by Paul Gilster | Sep 10, 2018 | Outer Solar System |
The announcement that the Dawn spacecraft is running out of its hydrazine fuel was not unexpected, but when we prepare to lose communications with a trailblazing craft, the moment is always tinged with a bit of melancholy. Even so, the accomplishments of this mission in its 11 years of data gathering are phenomenal. They also speak to the virtues of extended missions, which in this case gave us views and a wealth of information about Vesta but also a continuation of its stunning orbital operations around Ceres. And at Ceres it will stay, a silent orbiting monument to deep space exploration.
“Dawn’s legacy is that it explored two of the last uncharted worlds in the inner Solar System,” said Marc Rayman of NASA’s Jet Propulsion Laboratory in Pasadena California, who serves as Dawn’s mission director and chief engineer. “Dawn has shown us alien worlds that for two centuries were just pinpoints of light amidst the stars. And it has produced these richly detailed, intimate portraits and revealed exotic, mysterious landscapes unlike anything we’ve ever seen.”
Image: This artist’s rendering shows NASA’s Dawn spacecraft maneuvering above Ceres with its ion propulsion system. Dawn arrived into orbit at Ceres on March 6, 2015, and continues to collect data about the mysterious and fascinating world. The mission celebrated its ninth launch anniversary on September 27, 2016. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA.
Speaking of Marc Rayman, he deserves great thanks for his efforts at keeping an ongoing chronicle of Dawn operations available in his Dawn Journal. In his latest entry, Rayman notes how he always had to write these entries in haste because of his full schedule, but it’s the mark of a gifted narrator that haste is never an impression the reader comes away with. He has always seemed to be a patient and thorough writer who took the time to get things right.
The last two entries have been cases in point, describing the end of the Dawn mission and what is happening aboard the spacecraft. Immediately ahead is the final act, the loss of hydrazine that will eventually cause Dawn to lose the ability to orient itself — this could occur within weeks — and thus the spacecraft will no longer be able to point its solar panels at the Sun or its radio antenna at Earth (Dawn’s reaction wheels failed earlier in the mission, making hydrazine a critical factor). Radio silence will ensue. What happens next is an interesting question:
We also took a short look at the long-term fate of the spacecraft. To ensure the integrity of possible future exploration that may focus on the chemistry related to life, planetary protection protocols dictate that Dawn not contact Ceres for at least 20 years. Despite being in an orbit that regularly dips so low, the spaceship will continue to revolve around its gravitational master for at least that long and, with very high confidence, for more than 50 years. The terrestrial materials that compose the probe will not contaminate the alien world before another Earth ship could arrive.
So we have a window of about 50 years and perhaps more before Dawn will come down on Ceres, and Rayman’s inference here is that this gives time to mount another mission to Ceres before any contamination could occur. But given that it has also been 50 years since Apollo, I for one don’t necessarily see this as a very large window, and can only hope that its presence will be a motivator for a return to the dwarf planet before we have to wonder whether what we find there could have been affected by anything from Earth.
Dawn is the only spacecraft to orbit a body in the asteroid belt, and it is also the only spacecraft to orbit two extraterrestrial destinations, a feat that was accomplished thanks to its ion propulsion system. Dawn reached the 4.5 billion year old Vesta in 2011 and spent 14 months orbiting it, showing us a mountain at the center of the Rheasilvia basin that turns out to be twice the height of Mt. Everest, along with multiple canyons that fit into Grand Canyon scale. We also learned that Vesta, with its violent history, was the source of a common family of meteorites.
Ceres turned out to be even more of a surprise, with its bright salty deposits made up of sodium carbonate in the form of a slushy brine that originated from below the crust. Some regions on Ceres were geologically active in comparatively recent times, indicating a deep reservoir of liquid. Organic molecules turned up in the area around Ernutet Crater, but we lack the instrumentation aboard the spacecraft to be able to say whether they were formed by any biological processes. “There is growing evidence that the organics in Ernutet came from Ceres’ interior, in which case they could have existed for some time in the early interior ocean,” said Julie Castillo-Rogez, Dawn’s project scientist and deputy principal investigator at JPL.
With its high-resolution images, gamma ray and neutron spectra, infrared spectra, and gravity data, Dawn has delivered full value and continues, as this JPL news release reminds us, to “swoop over Ceres about 22 miles (35 kilometers) from its surface — only about three times the altitude of a passenger jet.” For his part, Marc Rayman thinks about Dawn after it goes silent as “an inert, celestial monument to human creativity and ingenuity,” which it is. But the data Dawn gathered still lives, and will resonate in the form of discoveries and new papers for decades.
by Paul Gilster | Aug 30, 2018 | Asteroid and Comet Deflection |
How extraordinary that we can sometimes tell so much from so little. Extraordinary too how careful we must be to make sure we’re not reading too much into small sample sizes. All of which brings me to the Japanese Hayabusa probe, a spacecraft that survived continual mischance on its journey to asteroid 25143 Itokawa, but was somehow able to return tiny grains of surface material to Earth. And using those materials, scientists are now revealing a violent past that tells us something not only about how the asteroid formed but what happened to it long after.
The work of Kentaro Terada (Osaka University) and colleagues, the investigation follows a complicated path back to the earliest era of our system. But let’s start with the sample collection, which almost didn’t happen: Already damaged from a major solar flare not long after liftoff on May 9, 2003, Hayabusa (the word means ‘falcon’ in Japanese) would also lose two of its three stabilizing reaction wheels. And when the command to deploy its Minerva mini-lander was given, the rover was lost.
Amidst these problems, JAXA (the Japanese space agency) scientists were finally able to bring the spacecraft into contact with the surface, enough so to disturb dust grains it could store for return to Earth. This would mark the first time the surface of an asteroid could be examined in the laboratory, and a decade of this investigation is yielding insights.
Image: The Hayabusa mission returned samples from Itokawa which are giving clues to the ancient history of the unusual asteroid. Image credit: ISAS, JAXA.
Scientists haven’t had a lot of material to work with, but it doesn’t take much. Examining micrometer-sized phosphate minerals using X-ray micro-tomography, the researchers have been able to perform isotope analysis of uranium (U) and lead (Pb), the latter enabled by Secondary Ion Mass Spectrometry (SIMS). This technique uses a focused ion beam on solid surfaces that causes the ejection of secondary ions that can be measured, revealing their molecular composition. Here’s how lead author Kentaro Terada explains the methods:
“By combining two U decay series, 238U-206Pb (with a half-life of 4.47 billion years) and 235U-207Pb (with a half-life of 700 million years), using four Itokawa particles, we clarified that phosphate minerals crystalized during a thermal metamorphism age (4.64±0.18 billion years ago) of Itokawa’s parent body, experiencing shock metamorphism due to a catastrophic impact event by another body 1.51±0.85 billion years ago.”
Itokawa was indeed formed some 4.6 billion years ago, in the formation period of the Solar System, but we also learn here that its subsequent life has been anything but serene. The second event Terada refers to would likely have been a collision with another asteroid.
Useful here is the comparison between the Itokawa particles and the composition of LL (Low (total) iron, Low metal) chondrites that fall to Earth. This work shows that the formation of Itokawa’s parent body was similar to that of typical LL chondrites — their mineralogy and geochemistry bear strong resemblances — but the collision history of Itokawa, with a catastrophic event 1.4 billion years ago, is significantly different from the ‘shock’ ages of most LL chondrites. The Itokawa shock history resembles, in fact, that of the Chelyabinsk meteorite.
The team goes deeper still, as witness this from the paper:
The observation of a deceleration in the rotation rate of Itokawa also constrains Itokawa’s evolution to within the last 0.1–0.4 million years during which period the conjunction of the two parts referred to as “head” and “body” by a low velocity impact occurred. This conjunction must have occurred after the disruption event and the subsequent main re-accumulation and possibly while the Itokawa fragments still resided within the main belt.
Itokawa was, in other words, pulverized by the collision revealed in these data, eventually reforming into the object we study today over a period of time. Following several billion years in the main asteroid belt, Itokawa was ejected by gravitational resonances into its current Earth-crossing orbit. Drawing on previous work on Itokawa orbits, the authors predict that at some point within the next million years, the asteroid will collide with Earth or else break apart.
Image: Back-scattered electron images of the Itokawa particles. (A–C) Show back-scattered images of polished sections of RA-QD02-0056, RA-QD02-0031, RB-QD04-0025, respectively. (D) Shows the “simulated” slice image of RB-CV-0025 before polishing, based on X-ray microtomography. Here, the angle and depth are selected where the cross sections inside two phosphates become the largest. (E) Shows the “actual” microscope image after careful manual polishing. Most phosphate grains are on the order of 2?µm?×?4?µm to 4?µm?×?5?µm in size. Credit: Terada et al.
Much rides here on the analysis of a very small amount of material, as the paper is quick to add:
…we emphasize that our successful chronology results for Itokawa are based on a single brecciated particle, RA-QD02–0056, that includes several apatite grains. Such a brecciated grain is so fragile that it may not have been collected if the Hayabusa spacecraft sampling mechanism had operated as planned and its impactors struck the Itokawa surface.
We learn, however, that the Hayabusa team has found other particles that may include phosphorus materials, so further studies should put tighter constraints on the violent events of Itokawa’s evolution.
The paper is Terada et al., “Thermal and impact histories of 25143 Itokawa recorded in Hayabusa particles,” Scientific Reports 8, published 7 August 2018 (full text).
by Paul Gilster | Aug 10, 2018 | Astrobiology and SETI |
Now that we’re getting closer to analyzing the atmospheres of terrestrial-size exoplanets, it’s worth remembering how difficult the call on the existence of life is going to be. Long-time Centauri Dreams contributor Alex Tolley takes on the issue in his essay for today, pointing out along the way just how easy it is to see what we want to see in our data. While we can learn much from terrestrial biology, new approaches looking at ‘pathway complexity’ may offer useful indications of biology and a set of markers not constrained by our own unique sample of life on Earth. A lecturer in biology at the University of California, Alex brings us up to speed with extending our methods of life detection in ways that are ‘biology agnostic.’ Expect controversy ahead — will we know life when we see it, and how can we be sure?
by Alex Tolley
Manuel Werner, CC BY-SA 2.5, https://commons.wikimedia.org/w/index.php?curid=633977
Life: [noun]? The condition that distinguishes animals and plants from inorganic matter, including the capacity for growth, reproduction, functional activity, and continual change preceding death. – Oxford Living Dictionary [6]
Life, like pornography, is notoriously hard to define, but we mostly recognize it when we see it. Life, as we know it, is identified by a set of features, which individually, may be shown by non-living systems. A classic example is “fire”, that can exhibit a simple metabolism (combustion), growth (size and spread), and even “reproduction” (sparks ignite new fires). Fire, however, fails the test of life, as all terrestrial life has the cell as a basic unit, which is not a feature of fire, nor can fire evolve.
Fossils are clearly not living, yet they show the order that life exhibits which indicates that they are a remnant of an organism that was living. For example, the fossilized skull of a dinosaur shows considerable order with features that indicate it was from a living animal and very similar to other fossil skulls of its type. Fossil bone fragments are far harder to identify and experts can detect these when a layperson would see only a piece of rock. Microfossils are even harder, as the controversial objects in the meteorite ALH84001 indicate [7]. Are they natural formations or organisms?
When we consider how to recognize extraterrestrial life, we are largely constrained by the single sample we have. That should not stop us looking for Earth-type life as the low hanging fruit, as Earth-type life is an existence proof and well worth searching for signs of, whether with telescopes or probes.
Recent focus has shifted to spectroscopic analysis of exoplanet atmospheres. The logic is largely that of James Lovelock’s Gaia hypothesis, where the production of certain gases is a proxy for their generation by life. For a terrestrial-like world in the habitable zone (HZ), the existence of both oxygen (O2) and methane (CH4) implies life as these are primarily produced by life on Earth in the ratios required to prevent equilibrium. For a world more like the Archaean Era, an atmosphere rich in methane but excluding other gases like carbon monoxide (CO) indicates bacterial methanogens, as the geological serpentinization of ultramafic rocks like olivine is insufficient to maintain the CH4 levels.
It is this geological reaction that makes the presence of CH4 in the Martian atmosphere so ambiguous, as the masses are small enough to be produced by geology as well as subsurface pockets of life.
Where we have extraterrestrial samples, such as carbonaceous meteorites, asteroids and the recent confirmation of organic material on Mars, there is a need to differentiate abiotic from biotic processes. The classic examples of biotic processes based on our Earthly sample include the chirality of amino acids and sugars, the isotopic changes of elements due to favored selection in biological processes, such as the reduced carbon-13/carbon-12 ratios, and the odd number of carbon atoms in many lipids.
As our planetary probes increase in sophistication, and the idea that subsurface icy moons might be hospitable for life, there is a need to include the instruments to test for possible biosignatures to try to reduce ambiguity.
Biology as a System
Returning to the question of recognizing life, a key point is that it exhibits a number of features that need to be present so that we can distinguish it from inanimate objects. For terrestrial life, the basic unit is the cell, which encapsulates all the components needed to exhibit the features we identify with life, maintaining order and fighting entropy, by interacting with the external world. With the evolution of photosynthesis, that order is maintained by the capture of a tiny amount of the energy emitted by our sun. This is now the dominant source of energy for the terrestrial biosphere. Even the simplest unicellular organisms require hundred of genes, and therefore unique functional protein molecules to maintain themselves. Higher organisms require tens of thousands of genes, producing hundreds of thousands of unique proteins to maintain their more complex structures and life cycles.
We can again see the problem of detecting life from limited features with the three Viking experiments that proved ambiguous. Had there been a microscope to view a culture, the presence of cells, their growth and reproduction over time would have clinched the presence of life.
While this approach can work for samples in our solar system, for exoplanets, we must rely on proxies that are primarily measurable using spectrographic techniques. Conceivably, a telescope could image a world, detecting seasonal changes in photosynthetic organisms, providing direct evidence. For worlds with life still only in its prokaryotic state, remote direct imaging of life may prove impossible.
For samples in our solar system, we can expect a search based on terrestrial life analogs, so the usual suspects will be searched – proteins with chiral amino acids, DNA, lipids with odd-numbered carbon atoms, as well as more subtle signs such as carbon-13/carbon-12 ratios. But we should also look for evidence that is terrestrial biology agnostic, especially if we are hoping to discover very different life forms from unique geneses.
Sara Seager: Going Beyond the Presence of a Molecule
Sara Seager’s team has been at the forefront of considering biosignatures beyond the usual proxies of atmospheric gas mixing ratios. Her paper [8] (see also CD post Ambiguity in Life Detection?, October 31, 2017) collated the range of small organic molecules that exist and their source whether biotic or abiotic or both. At the 2018 Breakthrough Discuss conference, she noted that biology does have some apparent constraints and explained the paucity of biotic molecules with nitrogen-sulfur (N-S) bonds, even though these compounds abound in industrial chemistry because of their usefulness. Terrestrial biology is rich with thiol reactions and has evolved replication and metabolisms that generally eschew molecules with such N-S bonds. This phenomenon constitutes a possible biosignature. While this is one specific example, there are likely many others. However, constraining our ideas to terrestrial biology may result in us missing non-terrestrial biologies that are different, providing false negatives. What is needed is a more general approach that is biology agnostic.
Lee Cronin: A Generalized Approach
Lee Cronin’s group has been formulating a more biology agnostic approach, one that is based on living organisms being homeostatic systems [4]. His approach is to assume molecules can be constructed by assembling sub-units and that this confers a minimal construction pathway, which he calls “pathway complexity”. One can consider this as a tree of all possible molecules composed of the building blocks with the number of construction steps needed to build the molecule. This is an indication of the non-randomness of the molecule. If a molecule in a sample is highly enriched compared to the possible random set of molecules that could be constructed at random, this is indicative of a construction pathway that in turn is indicative of life.
Figure 1 below shows the concept of construction of a specific molecule from building blocks.
Figure 1. Illustration of a complexity pathway in blocks, with the target shown by the yellow box. A combinatorial explosion in structures is illustrated by the other faded structures shown, which are just a small set of the many alternative structures that could be constructed. (Online version in color.) [4]
Figure 2. An illustrative graph of complexity against size of the state space. Orange regions are impossible as they are above or below the bounds of the measure. The green region is where living systems may be most probable, where structures are neither too simple to be definitively biological, nor too complex to exist at all. [4]
Cronin states? :
“We can extend the basic complexity measure above to cope with assessing the complexity of a group of objects that contain identical connection motifs (figure 5). In this case, we examine a population of objects and abstract out a common graph based on connected subunits that share features. For example, if examining a set of cups or mugs, then we can create a common graph of ‘handle connected to body’, regardless of potential variations in size/colour etc. If examining a set of human beings, then we could create a common graph of bone connectivity, ignoring variations in size/shape of individual bones, or any material in the body other than bones.”
He concludes:
“It is clear that biological and biologically derived systems have an ability to create complex structures, whether proteins or iPhones, that is not found elsewhere in nature. Assessing the complexity of such artefacts will be instrumental in searching for undiscovered biospheres, either on Earth [29] or elsewhere in the Solar System, and would make no assumptions about the details of the biology found. We propose Pathway Complexity as the natural measure of complexity for the production of artefacts. In this context, we argue that there is a critical value of Pathway Complexity above which all artefacts must be biologically derived. This approach provides a probabilistic context to extending the physical basis for life detection proposed by Lovelock [30]. In further work, we will show how this applies to a range of other systems, and propose a series of experimental approaches to the detection of objects and data that could be investigated as a possible biosignature. In the laboratory, we are interested in using this approach to develop a system that can explore the threshold between a non-living and living system. Pathway Complexity may also allow us to develop a new theory for biology. This might inform anew way to search for life in the laboratory in terms of the complex products a system produces and if they could have arisen in any abundance by chance, rather than trying to measure the intrinsic complexity of the living system itself.”
Kauffman: Self Organization Theory of Life
In 1993, Stuart Kauffman published The Origins of Order: Self Organization and Selection in Evolution [2]. I consider it a tour de force? in theoretical biology. Of relevance to this post are chapters 7 and 8 on the concept of autocatalytic sets, and the crystallization of metabolisms.
Autocatalytic sets are best thought of as a linked set of components, e,g, catalytic RNA, that can build each component from others in the set. The effect of which is to rapidly increase the RNA species included in the set. From an origin of life perspective, Kauffman showed that the probability of autocatalytic sets arising increases to unity as the number of RNA species increases. Metabolisms similarly crystalize when there are enough reactants so that a complete, self-contained metabolism can be sustained. Again, the probability of such a complete metabolism will increase as the number of reactants increase.
As Kaufmann states:
“Thus we arrive at a new point of view. The emergence of a connected metabolism as a supracritical web requires a sufficient complexity of organic molecules and a sufficient complexity of potential catalysts. At that point, such a connected web is an inevitable emergent collective property of the chemical system.”? [2] p348.
The relevance to Cronin’s work should be clear. Once a self-sustaining set of components appears, the components in that set will increase rapidly compared to others in the vast space of possible components. Cronin’s metrics, such as “pathway complexity” naturally emerge when considering the number of components compared to the possible components due to random reactions.
While Kauffman’s work is theoretical, Cronin has shown that lab experiments [5] support this basic concept. In terms of biology, they are agnostic in origin, therefore freeing us from focusing on terrestrial biology as our single sample of life, and informing us of possible biosignatures.
Biosignature Search
Sampling the compound space is not something that is likely to be possible anytime soon, if ever, using spectral analysis of [exo]planet atmospheres. Even Seager’s list of possible biosignature compounds are effectively trace compounds, and there is no way to determine whether her N-S bonds hypothesis works for an exoplanet from telescopic observations.
However, the solar system is another matter, and targets such as Mars, the plumes of Enceladus, the organics on the [sub]surface of comets, Ceres and the Europan sub-surface ocean are ripe for this sort of systems analysis using mass spectrometers and IR spectroscopy on probes to determine the mix of compounds in a physical sample.
While future telescopic observations that can image worlds directly may show up life as lush, boreal zones on exoplanets, nearer to home we may be able to sample the biological detritus of such worlds through wanderers like ‘Oumuamua that may have captured bacterial life from living worlds. If exoplanet life is largely bacterial, then probes sampling the upper atmosphere or even the surface can use this technique to determine if life exists without the difficulty of trying to cultivate bacterial colonies and observing the results. While interstellar probes that could sample such worlds are a relatively distant prospect, they are possible in the centuries to come using propulsion technologies that do not require new physics.
Conclusion
Confirmation bias involves seeing the data supporting what you are expecting. The lack of artificial objects in the heavens that is the context for the Fermi Question elicits polar views of “we are the only life” to “technological life is there, we don’t recognize it”. Similarly, the lack of unambiguous signals found by SETI results in a similar dichotomy. As we noted, the ambiguous objects in the ALH84001 meteorite that came from Mars have proponents for either proposition — life and non-life. Early searches for “missing links” in the evolution of humans that found a few bones and partial skulls also resulted in polar views of whether modern humans had evolved from an apelike ancestor or been created in his present form. We can be sure that any spectroscopic evidence of proxies for life – biosignatures – will be similarly interpreted.
So far, chemical analysis of samples in our solar system have been teasers, hinting at possible life, but no more. While a video of a living animal in a sample tube would be unambiguous (although there will no doubt be claims of “it is a hoax”), the most compelling approaches would be confirmation of DNA or proteins, preferably with no known terrestrial copies. This, however, assumes life is very similar to terrestrial life, and techniques used to find such molecules will miss life that may be very different from terrestrial life. Starting from the model that living systems are complex systems, yet not so complex as to be random, chemical analyses within the scope of that with existing analyzers may well be able to indicate life with far less ambiguity than the focus upon a few proxy molecules. In this regard, the theoretical bases described by Kaufmann and Cronin, and confirmed with experiments on terrestrial living organisms, offers perhaps the best approach for sampling probes that we can envisage in the near future, although the mass penalty of a microscope would be very much appreciated.
References
1. Petkowski J et al “Natural Products Containing a Nitrogen?Sulfur Bond” J. Nat. Prod. 2018, 81, 423?446
2. Kauffman S. “The Origin of a Connected Metabolism” ch 10, p343 in The Origins of Order, 1993
3. Domagal-Goldman S et al “Life Beyond the Solar System: Remotely Detectable Biosignatures” 2018, arXiv:1801.06714 [astro-ph.EP]
4. Cronin Lee “A probabilistic framework for identifying biosignatures using Pathway Complexity” 2017, Philos Trans A Math Phys Eng Sci. 2017 Dec 28;375(2109). pii: 20160342. doi: 10.1098/rsta.2016.0342.
5. Doran D et al “A recursive microfluidic platform to explore
the emergence of chemical evolution” 2017, ? Beilstein J Org Chem.? 2017 Aug 17;13:1702-1709. doi: 10.3762/bjoc.13.164. eCollection 2017.
6. http://en.oxforddictionaries.com/definition/life
7. http://en.wikipedia.org/wiki/Allan_Hills_84001
8. Seager, Bains and Petkowski, “Toward a List of Molecules as Potential Biosignature Gases for the Search for Life on Exoplanets and Applications to Terrestrial Biochemistry,” ? Astrobiology 16(6) (June 201), 465-485
by Paul Gilster | Jul 6, 2018 | Uncategorized |
Kelvin Long is a familiar face on Centauri Dreams, the author of several previous articles here and many publications in the field of interstellar studies. The creator of Project Icarus, the re-design of the Project Daedalus starship of the 1970s, Long was a co-founder of Icarus Interstellar and went on to head the Initiative for Interstellar Studies. He also served as editor of the Journal of the British Interplanetary Society during a critical period in the journal’s history, and authored Deep Space Propulsion: A Roadmap to Interstellar Flight (Springer, 2011). Today he turns his thoughts to catastrophe, and the question of what would happen to human civilization if it were reduced to a small remnant. Could we preserve the most significant treasures of our science, our culture, in the face of a devastated Earth? Exploring these ideas takes us deep into the past before turning toward what Kelvin sees as a possible solution.
by Kelvin F Long
The year is 2050. Earth is a thriving metropolis with a population exceeding 9 billion. Progress has been made in harmonising social-cultural tensions around the world and nation state war is now an infrequent event. A young child of the future steps out into the bright sunshine of a gorgeous new morning. Her day is still ahead of her as she out stretches her arms and smiles at the mellifluous call of the singing birds. But then looking up, she notices something in the distance, a long streak across the sky that is moving rapidly, and seems to be descending towards the ground. It disappears behind the horizon, and shortly later a blinding flash engulfs the world. The girl looks on stunned, eyes struggling against the light, to see the gradual build-up of a mushroom cloud that starts to reach high into the atmosphere. The impact event was hundreds of miles away, yet soon it engulfs the world in a global climate change and sends Tsunamis sweeping over coastal cities destroying all in the path. In response to oceanic earthquakes, the water becomes so big, that it pushes across the flat land masses; unrelenting mega white horses to a trampled poppy field below. One day, this will form into wedge shaped chevron deposits hundreds of feet high, composed of ocean floor micro-fossils. Within days of the event the girl will learn that billions of people are wiped out as the human civilization draws to a rapid stagnation. All infrastructure and governments are gone, and only small pockets of communities around the world survive, numbering thousands at best. She was one of the lucky ones, her small community of one hundred people survived just barely on their high mountain top position. This is fortunate for a girl named Hope.
Introduction
The future is uncertain. Whilst it is important to emphasise the positive reasons for the exploration of Earth and space, it is also important not to be in denial about the risks that really face us; for they are not insignificant. They are many and varied in type. From the potential for nation state warfare, to disease pandemics, to global climate change, to risks from above such as impact events by asteroids or comets or even the possibility alien invasion. The sure way to guarantee our survival is to follow the lead of Elon Musk and to make the human race an interplanetary species; and indeed to go further with an interstellar species. But until we have reached this point we are vulnerable. The proposal made in his article is not an alternative to the current plans for the colonization of space and the continued building up of infrastructure, but it is a complimentary pathway to increase the probability of human survival into the coming centuries. In particular, it should be taken on board that the assumptions of this project is that a possible future exists where rocket technology no longer even exists as a worst case survival scenario.
The Apkallu initiative is a proposed project to help reboot human civilization, on the assumption that some small pockets of human communities survive around the world during a global cataclysm, but all the remnants of our industrialised and developed civilization are destroyed. This includes our cities, our farms, our libraries, our infrastructure, and our transport networks; in essence the human race is thrown back to being a hunter-gatherer species and must begin again. It is named after the Sumerian sages who are said to have helped humankind establish civilization and culture and giving us the gifts of a moral code, mathematics, architecture, agriculture and all ways necessary to teach us how to become civilized. The Sumerian civilization is one of the first to appear in recorded history, which included the invention of its own writing form called Cuneiform. Before we discuss what the Apkallu initiative actually is, it is worth reminding ourselves of some essential context.
Impact Threats and Other Risks to Human Survival
We know that objects have impacted the Earth throughout its history and continue to do so today. Approximately 66 million years ago, it is believed that an impact event resulted in the Cretaceous-Tertiary (K-T) extinction. This led to devastation in the global environment and a prolonged winter which affected the photosynthesis of plants and plankton life. It also resulted in the destruction of a plethora of terrestrial organisms, including mammals, birds, insects and most famously the dinosaurs. The object, an asteroid or comet, was 10-15 km in diameter with a likely impact velocity of around 20 km/s and an associated kinetic energy of impact of around 30,000 – 1000,000 Gtons TNT equivalent, depending on the assumptions. It left an impact crater in the Yucatan Peninsula in Mexico, and likely created 300 feet high Tsunami’s over an impact zone of around 3,000 miles.
Another example is the Arizona Meteor crater, which was the result of a Nickel-Iron object around 50 m in size impacting the Earth 50,000 years ago. With impact velocities ranging from 2.8 – 20 km/s this would have impacted with an associated kinetic energy of 10.7 – 26.2 Mtons TNT equivalent. Today, a crater remains of the impact event, 1.2 km in diameter and over 550 feet deep.
In 1908 a comet is believed to have impacted eastern Siberia, causing a flattening of a forest 2,000 square km in size. Since no impact crater was found, it is believed that the object disintegrated at an altitude of 5 – 10 km above the ground. The estimated energy of the air burst explosion was 10 – 15 Mtons TNT equivalent; depending on the assumptions one makes.
In July 1994 a comet split into 21 fragments ranging in size up to 2 km, and impacted the upper atmosphere of Jupiter with an impact velocity of around 60 km/s. The total energy of these impacts was around 6,000 Gtons TNT equivalent creating dark red spots with some being 12,000 km in size. Had this comet impacted the Earth, it would have posed a major threat to human existence.
During late 2017 we observed the close flyby pass of an asteroid of interstellar origins named ‘Oumuamua. Much of the nature of this objects remains uncharacterised, but some sensible estimates of the maximum potential impact energy suggest 4.2 – 46.9 Gtons TNT equivalent, had it impacted the Earth.
Then in April this year that an object named Asteroid 2018 GE3 passed closed to Earth and was spotted 119,500 miles away, which is closer than the Moon, which orbits at an average distance of 238,900 miles. The object was first observed by the NASA funded Catalina Sky Survey project based at the University of Arizona Lunar and Planetary Laboratory. It was first observed a mere 21 hours before the closest approach to the Earth. The object was estimated to be at least 150 – 360 ft in diameter.
How many more are out there waiting for us? No doubt some will argue that the impact risks are statistically small and we should not be concerned about them. We know there are many asteroids in our own Solar System, varying in size from 1 m up to 1,000 km. Approximately 16,000 objects have been found near Earth, but this is a small fraction of the estimated total that is out there, which varies between 1 – 2 million. Statistically, this presents a threat to human existence and life as we know it. Indeed, it is the belief of this author that impact events which can lead to global devastation of the human population may be as frequent as 1/1,000 – 1/10,000 years.
In addition to impact risks there are many other threats to human existence. This may include the implications of magnetic field reversal. Such an event occurred 41,400 years ago during the last ice age, called the Laschamp event. It caused a magnetic field reversal leading to a drop in its strength. This resulted in more cosmic rays reaching the Earth and an increased production of the isotopes Beryllium 10 and Carbon 14.
There are also the risk of enhanced solar activity such as through large scale solar flares, or the possibility of the Sun entering unstable periods in its evolution for which are current models of stellar-structure are not aware. This could be due to the passage of our Sun through the spiral density arms of the galaxy. There are the risks of nation state war or even global thermonuclear war that could drive us towards extinction, either through direct destruction or through altering the climate. There are the risks of human disease pandemic, which surely must become more probable in an increasing global population. There are the risks of human destruction of elements of the biosphere, such as pollutions of the oceans, soils, deforestation or polluting of the atmosphere. There are the risks that microbes could be introduced into our biosphere from an alien planet that is infectious to our biodiversity.
Then there is the actual risk of alien invasion, from a species set on conquering other lower species or seeking resource acquisition no matter the costs. It may be assessed that some of these are low probability. However, the fact that there are so many risks to the future survival of humankind should be a concern, and it is vital that we take a proactive approach to adaptability and survival, instead of a reactive one when such events occur.
Assumptions of a hypothetical Near-Human Extinction
Imagine a situation where human kind is nearly wiped out by some global cataclysm. This could be an impact event or one of the other risks highlighted earlier. In a worst case scenario, but one where some humans survive, we might make the following assumptions:
- 1. All infrastructure is destroyed, to include buildings, power utilities, city plumbing, dams, transport networks, agriculture and farming, huge portions of the plant and animal kingdom.
- 2. All information sources are destroyed, to include all the world libraries, computers and electronic memory. It is possible that some books will be discovered over time as communities explore the rubble remaining from the metropolis. Books would become precious beyond their current value.
- 3. The global climate is in turmoil and hostile, but with isolated regions of stability such that with determination survival is possible.
- 4. The geological, climatic, oceanic activity and effects of the cataclysm event, within weeks, months or years will gradually return towards some level of stable Earth.
- 5. Small pockets of humans survive around the Earth, perhaps 10s to 100s each but with the total not exceeding thousands.
Given this scenario, we can note that the surviving generation will remember the world as it was before. They will use this knowledge to teach their children. At this point knowledge is based upon direct memory. Those children will then grow up, with their parents dying off, and they will remember what their parents taught them and some of those children may even have some memories of the world before. But for the most part we are dealing here with recent history and part mythology. The grandchildren will also be born and grow up, but they will have no direct memory of the world the way it was before. At this point we are dealing with history and mythology. Within the third or fourth generation there is a risk that all knowledge will be lost, and especially if that knowledge is not captured and written down. All received knowledge then becomes both mythology and fantasy.
There are solutions to this practiced by the Native North Americans for example, which is to communicate stories verbally and also use this to impart wisdom, and those stories are accompanied by rituals. However, one cannot believe that such a method of communication does not contain significant information error propagation with each successive generation, compared to the original version.
The History of Humans on Planet Earth
In the event of a global cataclysm, assuming small pockets of human communities survive, but the majority of human civilization and associated technological infrastructure is destroyed, how can we ensure a chance at rebooting human knowledge? Indeed, is it possible that this has in fact occurred in the recent past and this is a part reason for the many Megalithic structures on Earth?
Until recently, Sumer was the earliest known civilization in the historical Mesopotamia, and is located in modern Iraq. It dates back to 3,000 B.C and was likely settled around 4,000-5,500 B.C by proto-Euphrateans or Ubaidians. The people from this era are credited for many great inventions and discoveries which led to the advance of their society. This includes in mathematics, geometry, agriculture, architecture, economics and law to name a few. One of the most famous objects discovered from this period is the Code of Hammurabi, a 2.25 m tall stone wall consisting of 282 laws, such as “an eye for an eye” and is the first legal system from the Old Babylonian period.
The Code of Hammurabi, created 1750 B.C, currently housed at the Louvre, Paris (image credit: K. F. Long)
It is important to note that in the Babylonian creation mythologies, which were written in Cuneiform, there are around a thousand lines of text on seven clay tables. The focus of this text is the creation of humankind for the service of the gods. These texts are called the Enûma Eliš, and arguably they have a clear lineage to the Judeo-Christian Bible. The Cuneiform script was scribed, using a wedge-shaped marker onto a wet clay tablet and also cylinder seals. These are small round objects typically an inch in length engraved with information. Once dried the inscription was permanent. The information preserved on tablets and seals was Cuneiform text but also contained figurative scenes or descriptions of events or objects. Such objects are breathtaking in their clarity, gorgeous in their artistic nature, and contain a wealth of information about the society, its rituals, values, business, science and technology.
Photographs of Sumerian Cylinder Seals from the Private Collection of the Author (image credit: K. F. Long)
The Holy Bible records a flood story that engulfed all of planet Earth. This is recorded in Genesis chapters 6 – 9, and the flood seems to last for around one hundred and fifty days. Other cultures have recorded similar stories. For example the Sumerian tale of Ziusudra and the Atra-Hasis also describes a global flood story that is similar to that told in Genesis. In the Sumerian story the flood lasts for seven days. An account is also told in the Epic of Gilgamesh, which is more similar to the Biblical story. Also, the Hindu mythology tells of a great flood in the Satapatha Brahmana. It is very easy to dismiss the possibility of a global flood as pure mythology, but the occurrence of a similar story in so many cultures around the world is at least suggestive that it may be a memory of an actual event which many today are regarding as mythology. Indeed, science may be catching up with the past.
Geologists and climatologists study a period in Earth’s history called the Younger Dryas, which occurred 12,900 to 11,700 years ago and saw a return to glacial conditions which temporarily reversed the gradual climatic warming after the last glacial maximum which began receding around 20,000 years ago. It led to many catastrophic effects including the decline of the Clovis culture in North America and the extinction of many megafauna which included the Mammoths; the last of which survived into the Holocene around 4,500 years ago in Africa, Europe, Asia and North America.
Illustration of the Younger Dryas period
In recent years, evidence is emerging that the Younger Dryas period may have been caused by a cometary impact event on the North American ice sheet, around 12,900 years ago. The evidence for his includes the discovery of a 10 million ton deposit of impact spherules across four continents, and the discovery of a Nano-diamond rich layer. In addition, analysis of underground soils indicates massive wildfire and abrupt ecosystem disruption on California’s Northern Channel Islands. Scientists have also discovered very high temperature impact melt products as evidence for an air burst explosion. All of this is dated to around 12,900 years ago, at the onset of the Younger Dryas. If this is proven to be correct, then a global cataclysm may indeed have occurred in our recent past. Speculating, if any advanced civilizations existed on Earth prior to this date, they may have been wiped out by this cataclysm forcing civilization to start from the beginning again.
At some point in our past we moved from a hunter-gatherer species to an agricultural-farming one, where we embraced the domestication of animals and crops. This is marked by a period called the Neolithic, and occurred around 10,200 years ago. It is considered to be the last period of the stone age and commenced the beginning of the Neolithic revolution. It ended with the emergence of the Copper and Bronze and Iron ages and our new abilities to use metals. It is remarkable that we have apparently exploded technologically and social-culturally over the last 10,000 years or so to the state where we have computers, cars, aeroplanes and communication satellites. What was it that propelled us forward over such a short space of time? Why had we not achieved this level of maturity previously? Was it the formation of a critical population density? Was it global climatic conditions? What is our tribal nature and inability to get organized? What it some other threats to our existence?
Homo sapiens in our modern form may be several hundred thousand years old. Paleolithic cave art certainly goes back to 40,000 years but may be 60,000 years if we include what is currently being claimed to be art from Neanderthal man. Evidence from the out of Africa hypothesis puts homo sapiens at around 130,000 – 180,000 years old. But there are alternative versions which claim populations emerging out of Africa as early as 350,000 years ago. Evidence for older findings includes discoveries of anatomically modern human skull fossils at Jebel Irhour in Morocco (315,000 years) and Middle Awash in Ethiopia (160,000 years). The history of human evolution is far from settled and ‘thinking man’ may be much older than we realised.
Ancient Megaliths
A story from ancient Sumeria is that of an amphibious being called Oannes (also known as Adapa) who apparently taught humankind wisdom. The story was told by Berossus in 290B.C, a Chaldean Priest in Babylon. Berossus described Oannes as having the body of a fish but underneath the figure of a man. He is said to dwell in the Persian Gulf, rising out of the waters in day time and furnishing humankind in the instruction of writing, arts and other subjects. Here are the words of Berossus:
“At first they led a somewhat wretched existence and lived without rule after the manner of beasts. But, in the first year appeared an animal endowed with human reason, named Oannes, who rose from out of the Erythian Sea, at the point where it borders Babylonia. He had the whole body of a fish, but above his fish’s head he had another head which was that of a man, and human feet emerged from beneath his fish’s tail. He had a human voice, and an image of him is preserved unto this day. He passed the day in the midst of men without taking food; he taught them the use of letters, sciences and arts of all kinds. He taught them to construct cities, to found temples, to compile laws, and explained to them the principles of geometrical knowledge. He made them distinguish the seeds of the earth, and showed them how to collect the fruits; in short he instructed them in everything which could tend to soften human manners and humanize their laws. From that time nothing material has been added by way of improvement to his instructions. And when the sun set, this being Oannes, retired again into the sea, for he was amphibious. After this there appeared other animals like Oannes.“
Whether this is pure fiction or has any resemblance to historical events does not matter, but it is this story that has given rise to the idea of building what this author is calling a ‘minilithic artefact’ under the Apkallu Initiative as will be discussed further below. As an aside it is worth noting that in his book Intelligent Life in the Universe, written with L. S. Shklovskii (Pan Books, 1977), the astronomer Carl Sagan opened a discussion on the Sumerian civilization with “I came upon a legend which more nearly fulfils some of our criteria for a genuine contact myth”.
On planet Earth we know that species rise up and fall and suffer extinction. The fossil record has shown this for many a species. There are also arguments that Homo Sapiens are not the only occurrence of intelligence on Planet Earth (see for example the recent book Other Minds by Peter Godfrey-Smith’ on the Octopus, William Collins, 2016). Why then is it not possible, in the last million years, that an earlier species of man, or other life form on Earth, could have evolved to similar levels of intelligence to that which we possess today, to include a technological level similar in extent? Such a people would predate modern recorded history, and it is at least plausible that some memory of them could be preserved in the creation mythologies of our various ancient cultures.
Many ancient Megalithic structures have been found by archaeologists around the world. This includes for example the Great Pyramid and the Great Sphinx in Giza (4,500 years old), Tiwanaku and Pumapunku in West Bolivia (3,500 years old), Stonehenge in England (5,000 years old), Machu Picchu in Peru (550 years old) to name a few. However, recently our linear understanding of human evolution from a hunter-gatherer species to an agricultural-farming one has been placed under scrutiny, by the discovery in 1996 of G?bekli Tepe, a site in the South eastern Anatolia region of Turkey, which may date back to 12,000 years old. The site demonstrates a superior knowledge of construction techniques, geometry and other disciplines and to enable its construction would have required a food surplus to exist – before the arrival of the Neolithic revolution. In addition, it is arguable that to get to a point where you can construct something like G?bekli Tepe would take thousands of years of advancement of knowledge in itself. This might suggest that the builders were 15,000 – 20,000 years old.
A potentially even older site has also been found in West Java, called Gunung Padang, which was discovered in 1914. It may be the largest megalithic site in South Eastern Asia. Radiocarbon dating puts the site at several different eras spanning 6,500 – 20,000 years ago, although the dating claims are controversial among archaeologist in Indonesia. A large structure has also been discovered beneath the surface some 15 m down and includes large chambers. This discovery, and that of G?bekli Tepe, is telling us that our linear understanding of history is in need of revision.
Interglacial Periods in Earth’s History
Given the existence of G?bekli Tepe and Gunung Padang, the idea that an earlier intelligent and advanced civilization existing on Earth is not so implausible. However, were there opportunities in Earth’s history for this to occur? An examination of climatic conditions would seem to suggest so.
During the history of Earth there have been five major ice ages, and we are currently in the Quaternary Ice Age at this time, which spans from 2.59 million years ago. Within the ice ages are sub-periods known as glacial and interglacial periods.
Recent measurements of the relative Oxygen isotope ratio in Antarctica and Greenland show the periods of glacial and interglacial periods throughout history over the last few hundred thousand years. This is a measurement of the ratio of the abundance of Oxygen with atomic mass 18 to the abundance of Oxygen with atomic mass 16 present in ice core samples, 18O/16O, where 16O is the most abundant of the naturally occurring isotopes. Ocean water is mostly comprised of H216O, in addition to smaller amounts of HD16O and H218O. The Oxygen isotope ratio is a measure of the degree to which precipitation due to water vapour condensation during warm to cold air transition, removes H218O to leave more H216O rich water vapour. This distillation process leads to any precipitation having a lower 18O/16O ratio during temperature drops. This therefore provides a reliable record of ancient water temperature changes in glacial ice cores, where temperatures much cooler than present corresponds to a period of glaciation and where temperatures much warmer than today represents an interglacial period. The Oxygen isotope ratios are therefore used as a proxy for temperature changes by climate scientists.
The Vienna Standard Mean Ocean Water (SSMOW) has a ratio of 18O/16O = 2005.2×10-6, so any changes in ice core samples will be relative to this number. The quantity that is being measured, ?18O, is a relative ratio calculated as in the units of % parts per thousand or per mil. The change in the oxygen ratio is then attributed to changes in temperature alone, assuming that the effects of salinity and ice volume are negligible. An increase of around 0.22% is then defined to be equivalent to a cooing of 1?C.
There are differences in the value of ? between the different ocean temperatures where any moisture had evaporated at the final place of precipitation. As a result the value has to be calibrated such that there are differences between say Greenland and Antarctica. This does result in some differences in the proxy temperature data based on ice core analysis, and Greenland seems to stand out, such as indicating a more dramatic Younger Dryas period (11,600 – 12,900) than other data.
An analysis of this data shows that the climate has varied cyclically throughout its history and is manifest of natural climate change. In particular what emerges out of the data are some interesting lessons about the recent history of planet Earth. Data shows the rapid oscillations of the climate temperature from the average temperature of today, indicative of glacial and interglacial periods. In particular, the data shows that during the Holocene period, beginning approximately 11,700 years before present, the temperature varied between 2-4 ?C.
It is reasonable to assume that human civilizations under development will do better when the climate is kinder. This means that the warmer it is the better civilisations will do, and the colder it is, the harder the struggles. In particular we can expect that during the conditions of a colder climate that agricultural farming will suffer, and so there will be less food to go around, which will affect both lifespan and population expansion. To support this it is worth noting that the current epoch, the last 10,000 years has been one of the longest interglacial period for at least the last quarter of a million years and it is reasonable to therefore assume that this is one of the factors which has allowed human development from the emergence of the Neolithic period coming out of the last ice age.
The data also shows that there was a large global warming period known as the Eemian around 115,000 – 130,000 years ago. The average global temperatures were around 22 – 24 ?C, compared to today where the average is around 14 ?C. Forests grew as far north as the Arctic circle at 71? latitude and North Cape in Norway Oulu in Finland. For comparison North Cape today is now a tundra, where the physical growth of plants is limited to the low temperatures and small growing seasons. Given that homo sapiens may have been here since around 300,000 years ago, this seems like a major opportunity for the development of human society from a people of hunter gatherers to one of agricultural developers and the development of a civil society.
There have been other interglacial periods that have resulted in global temperatures being either equivalent or above the average today, and the data shows temperature spikes of periods at around 200,000 years, 220,000 years, 240,000 years, 330,000 years and 410,000 years. Each of these interglacial periods will typically last at least 10,000 years.
Temperature Proxy Data Showing Opportunities for the Rise of Advanced Civilization in Recent Prehistory
The Apkallu Initiative
It is fully admitted that much of the above contains speculation, but until we have a firmer grasp of history it would be unwise to rule such possibilities out. We turn our attention then to the future and solving the problem of how to preserve human knowledge in the event of a global cataclysm such that humankind can restart again so that within centuries we mature back to similar levels of today’s technological advancement. Ultimately this is a statistical problem, in that by reducing the time of each cycle for maturing to technological capability, one improves the probability of survival. It is sensible to think of this concept as a civilization accelerator.
The Apkallu Initiative is therefore a proposal to construct a minilithic artefact (analogous to Megalithic artefacts) that can survive for a time duration exceeding 100,000 years. This duration is chosen for three principal reasons:
- 1. The recent ice core records suggest that within that time period there may be several opportunities (~4) where the climatic conditions are sufficiently supportive for human existence to facilitate growth beyond basic survival.
- 2. It approximately corresponds to four processional cycles of the Earth around the equinoxes, which typically last 25,920 years. We note that many of the ancient Megaliths seem to have been preoccupied with the measurement of the equinoxes; which may relate to lost memory of previous cataclysms.
- 3. It is difficult to design for an artefact that can survive longer than this, although desirable.
The artefact would be a form of archaeological-architectural device from the standpoint of future humans who uncover it. The device would be replicated perhaps 1,000 times and distributed around the seven continents of the Earth. Ideally, some could also be placed in space, on the Moon or Mars. The idea is that any future human surviving a global cataclysm that finds this artefact and studies it sufficiently, it will give them the knowledge they need to rapidly advance human civilization at an accelerated rate.
Painting illustrating future man finding the archaeological artefact (credit: K. F. Long)
The artefact would be a form of long distance communication. We have of course attempted message plaques in the past such as the Voyager Golden Record and the Pioneer Plaque. Indeed, the Code of Hammurabi from the Sumerian civilization is a form of minilithic artefact, but just specific to moral and legal codes. Another example would have been the tablets for the Biblical Ten Commandments.
There is a question of what materials to construct the artefact from. Plastics and metals will likely degrade over thousands of years. Electronic memory is not useful if it is subject to flip switching and also requires a computer interface to read it. It therefore seems sensible to construct the artefact out of stone; perhaps in a similar manner to the Sumerian Cuneiform on wet clay tablets. One of the options may be Diorite. It would perhaps be useful to depict both logograms, with syllabic and alphabetic elements, as well as phonetics and even determinatives to create appropriate semantic descriptions.
There is a question of what information should the artefact contain. It should contain the foundation knowledge of human civilization. This is a subjective decision. One example we might take lessons from for example was the Trivium (logic, grammar, rhetoric) and the Quadrivium (arithmetic, geometry, music, astronomy) of the classical world. Both were considered preparation work before delving into the study of philosophy and theology. In addition to these, the artefact might contain many other disciplines of thought, such as human biology, medicine, architecture, chemistry, physics, law, history, music, language, agriculture, botany, ethics and other subjects. Experts in appropriate disciplines would need to be consulted to derive the say 12 base foundation knowledge or tenets that govern a field from which in principle all else can be derived given time.
The goal of the information content imprinted onto the artefact would be as follows:
- Goal 1: The continued survival of the human species at peace.
- Goal 2: The accelerated technological, social-cultural growth of human civilization from an assumed stagnated level.
- Goal 3: The preservation of moral and ethical philosophy
There is also a question of what language. One approach would be to take lessons from historical artefacts which contained several languages to ensure future interpretation. This includes the Rosetta Stone (2,200 years old) which contains ancient Egyptian hieroglyphics, demotic and ancient Greek. Another example is the Fuente Magna of the Americas (5,000 years old), found in Bolivia but contains both ancient Pukara and a proto-Sumerian alphabet. Another example is the Behistun inscription (2,500 years old) found in Iran, which contains three different cuneiform script languages, that of Old Persian, Elamite and Babylonian.
There is also the question of the size and shape of the artefact, and although you want it big enough to find, you also want to manage the construction cost of the project. Something around 6 – 12 inches would seem a good optimum size. The exact shape would have multiple surface areas to facilitate different disciplines of knowledge. One idea is a Dodecahedron, which has 12 faces.
The proposal of the Apkallu Initiative is to form a team which then designs and leads the construction of such an artefact. This can then be reproduced and distributed to different locations around the world. Some would eventually be displayed in art galleries or museums and some will be lost to the land and sea, but the hope is that in the event of the cataclysmic scenario described above that future human will stumble across such an artefact, and after studying it, teach their community everything they need to become a civilized and socially-technologically advanced society. Currently no team has been formed, but this article is an initial invitation of interest and anyone interested can contact the web site: https://www.apkalluinitiative.com/
Our ability to become an interstellar capable species depends in the near term on our ability to survive here on Earth or in near-space. The preservation of the deep knowledge and learning of the human experience is critical to this future, if we are to continue to progress, avoid stagnation and decay or even complete extinction or avoid repeating mistakes of the past.
Finally, such a project has the potential to inspire long-term thinking among differing human societies, and so in itself may be a self-perpetuating mechanism toward social-cultural harmonization and increased global awareness of our fragility in the great Cosmos. In addition, because of its interdisciplinary nature, it has the potential to involve all of humanity on its journey, as we jointly work toward a back-up plan to ensure that humanity can survive in the millennia ahead.
The author dedicates this article to the efforts of Graham Hancock and Randall Carlson, whose significant research inspired this initiative. It was written to garner scrutiny of the idea, before deciding whether to proceed or not. Feedback is invited.
by Paul Gilster | May 18, 2018 | Astrobiology and SETI |
Ronald Bracewell’s name doesn’t come up as often in these pages as I might like, but today James Jason Wentworth remedies the lack. Bracewell (1921-2007), active in radio astronomy, mathematics and physics for many years at Stanford University, developed the concept of autonomous interstellar probes. Such a craft would be capable not only of taking numerous scientific readings but of communicating with any civilizations it encounters. His original paper on these matters dates back to 1960 and relies on artificial intelligence, long-life electronics and propulsion methods that don’t necessarily involve high percentages of c. Jason considers these factors from the perspective of 2018 and explains what a program sending such probes to numerous stars might look like. If you’re recalling Arthur C. Clarke’s ‘Starglider’ from The Fountains of Paradise, you’re not alone, but as the author notes, there are quite a few directions in which to take these ideas.
by J. Jason Wentworth
The writer wishes to extend his special thanks to Ellen N. Bouton, Archivist, at the National Radio Astronomy Observatory, for locating and providing a scan of Dr. Ronald N. Bracewell’s June 1, 1974 Stanford University Alumni Conference lecture, “Studies of Extraterrestrial Life” (Reference 25), and to Jim Hassel, Library Technician at the Rasmuson Library, University of Alaska Fairbanks, for providing scans of the Nature and American Journal of Physics articles (References 21, 22, and 23).
Starflight and the Matter of Time
The problems of interstellar spaceflight, more than any other type of travel, whether on Earth or in space, are inextricably bound up with time. This is true of starprobes as well as starships. Everything about starflight—from the choice of onboard power systems to the desires of the mission personnel (and those who fund the missions) to see the final mission results, and everything in between—is determined, or at least heavily influenced, by the lengths of the journeys. Insisting on rapid trips compounds the difficulties and costs of the missions, while being content to accept longer transit times eases their engineering (and financial) challenges, including those posed by cosmic rays and physical erosion. Lower interstellar cruise velocities also make stellar rendezvous missions less difficult. However, settling for slower interstellar passages introduces another possible cause for partial or total mission failure—the breakdown of components and systems due to aging and wear. The planners of interstellar missions must arrive at acceptable compromises between these and other competing, and sometimes diametrically opposed, factors. Longer missions also exacerbate another, all-too-human problem, which would be present even for the fastest possible missions: the long intervals between departure and arrival at distant stellar systems. Fortunately, there are countervailing factors which may—of necessity, in some cases—make slower interstellar missions acceptable, and even desirable.
Just as the Galileo and Cassini spacecraft examined asteroids and/or Venus while in flight to their destination outer planets, there are other, closer interstellar worlds that starprobes may be able to investigate while en route to other stars. If interstellar asteroids like 1I/2017 U1 (‘Oumuamua) are as common as some astronomers suspect, interstellar probes may have more to do while in transit than collecting fields and particles data and making VLBI (Very Long Baseline Interferometry) radio astrometric observations. Indeed, it would be prudent, in the interests of the probes’ safety—and to collect population statistics of use to future starship missions—for them to keep a constant watch for such objects, as well as for ejected comets, rogue planets, and even brown dwarfs, all of which (even if observed from afar) would be scientifically rewarding targets of opportunity. [1]
But before such interstellar probe missions can come to fruition, it will be necessary to develop electronics and power systems that can operate reliably in interstellar space for decades, centuries, or even longer. We will have to create machines which are, for practical purposes, immortal. While no such devices have been developed for consumer use (where “planned obsolescence” appears to often be a design factor), it is not uncommon for electronic devices—including solid-state ones—to remain perfectly functional for decades. As Dr. Ronald N. Bracewell (the electrical engineer and radio astronomer who developed the interstellar exploration/messenger probe concept that bears his name) pointed out in his 1974 book The Galactic Club: Intelligent Life in Outer Space, the lifetimes of electronic components and systems could already, at that time, be accurately predicted (an engineering capability that had existed long before he wrote the book).
He gave an extreme example, to demonstrate how even the lifetimes of large, distributed electronic systems operating in hostile environments can be known. A transatlantic submarine telephone cable contains many amplifiers built into the cable along its length, with each amplifier containing many vacuum tubes (not transistors, he found interesting to note). The entire cable is required to operate as a functional whole for twenty years under water (and hopefully longer). But even though none of these cables’ components had been subjected to a twenty-year test, engineers were able to simulate such tests for entire cables with confidence. The service lifetimes of transistors, he noted, could also be determined, because their deterioration depends in a calculable way on their temperature. If they were maintained at very low temperatures, which is easily done between the stars (and even, with known techniques, closer to a star), electronic devices could easily have indefinite lifetimes. Bracewell also suggested that if it proved necessary, some components could even—in a manner foreshadowing today’s 3D printing—be produced aboard interstellar probes as they neared their destination stars. [2]
Another enemy of such probes (and their electronics) is radiation and particle impact erosion, but these obstacles also appeared to be straightforwardly solvable to him. Referencing an article by I. R. Cameron in the July, 1973 issue of Scientific American (“Meteorites and Cosmic Radiation”), Bracewell noted in his book that the laboratory-measured rates of erosion on meteorites in space (between 0.2 to about 10 millimeters per 1 million years, depending on the meteorites’ compositions—and undoubtedly, where in interplanetary space they spent their lives after being exposed to space) indicated that a quite thin coating would suffice for protecting interstellar probes from erosion. [3] More recently, NASA and the Korea Advanced Institute of Science and Technology (KAIST) have been developing—and have working prototypes of—self-healing electronics for “spacecraft on a chip” vehicles. These devices can accept cosmic ray damage and then heal themselves (between 1,000 and 10,000 times, so far). [4]
Image: Ronald Bracewell (left), with Stanford’s Von Eshleman, a key figure in early research into gravitational lensing. Here the two are examining the horn antennae that Bracewell used in 1969 to determine that the Sun is moving relative to the cosmic background radiation. Credit: Linda Cicero/Stanford University.
Examples of Long-Life Spacecraft
Even today, there are examples of unexpectedly long-lived spacecraft, and this bodes well for the prospects of developing essentially immortal interstellar probes. The Sun-orbiting Pioneer 6, 7, 8, and 9 spacecraft, which were launched between 1965 and 1968, lasted for decades past their six-month design lifetimes; indeed, all of them except Pioneer 9 (which failed in 1983) may still be functioning. These probes have seldom been listened to since the 1980s (the spacecraft were last monitored between 1995 and 2000). [5] The Pioneer 10 and 11 outer planet probes (launched in 1972 and 1973, respectively) operated until 2003 and 1995, respectively. The Pioneer Venus Orbiter functioned in the hostile thermal and radiation environment near Venus between 1978 and 1992 (when it burned up in Venus’ atmosphere), and Voyager 1 and 2 are in their 41st year of operation. Even older spacecraft continue to function, and two—despite decades of exposure to Van Allen belt radiation—came back to life after having fallen silent many years before.
Three of the U.S. Air Force’s LES (Lincoln Experimental Satellite) spacecraft have exhibited this unexpected longevity. LES 1, launched in 1965, was last heard from in 1967—until a British amateur radio operator heard its signal in 2013. [6] LES 8 and 9, launched together into geosynchronous orbit in 1976, are still operating 42 years later. [7 and 8]. In 1974, the AMSAT-OSCAR 7 (AO-7) ham radio satellite was launched into a near-polar, Sun-synchronous orbit as a “hitch-hiker” payload, from Vandenberg Air Force Base. It fell silent in 1981 when its battery shorted, and 21 years later it was heard again (after its short-circuited battery went open, allowing the satellite to operate on its solar cells when in sunlight). Despite its decades of passages through the Van Allen radiation belt, AO-7 remains fully functional, with all of its beacons and transponders operational when it is in sunlight, which is most of the time. [9]
Another long-lived spacecraft is ISEE-3 (the third International Sun-Earth Explorer, launched in 1978, which was re-named ICE—International Cometary Explorer—for the occasion of its 1985 encounter with Comet Giacobini-Zinner). After its many adventures (including multiple lunar flybys), it was re-contacted and operated by the private ISEE-3 Reboot Project in 2014. It may still be operable when it passes near the Earth again in 2031. [10]
Interstellar Probes that Can Learn and Make Decisions
While pre-programmed digital electronic computers would likely be sufficient for “fly-through” interstellar probes, stellar rendezvous probes would likely need to be able to learn and to make decisions for themselves (for seeking exoplanets around their destination stars, entering circum-stellar orbit in the proper plane and orbital direction, computing flyby trajectories to enable close examination of the system’s planets, etc.). This would especially be the case for Bracewell probes, which would also listen for any local, intelligently-produced radio and/or laser signals and attempt to contact any such civilizations, then learn their language(s) in order to act as local scientific and cultural emissaries of humanity. This would include informing the “local aliens” about how and where to contact the Earth directly, via interstellar radio and/or laser transmissions.
Analog computers, as the British biologist Rupert Sheldrake has pointed out, “enable complex, self-organizing patterns of activity to develop through sometimes chaotic, oscillating circuits.” He also noted that in 1952, William Ross Ashby, a British cybernetics researcher, published a book titled Design for a Brain, in which he showed how analog cybernetic circuits could model brain activity. More recently (as Sheldrake also noted), Mark Tilden developed insect-like robots that demonstrated self-organization—and even learning and memory—despite the fact that these devices contain fewer than ten transistors and have no computers in them. [11 and 12] BEAM (Biology Electronics Aesthetics Mechanics, or Biotechnology Ethology Analogy Morphology) robotics, a “reaction-based” type of machine building, was inspired by Tilden’s work. (In the nearer term, analog logic circuits-containing robots such as Tilden’s would be useful as rovers, “hopper” rovers, winged and aerostatic aerobots, instrumented boats, and submersibles for exploring planets, moons, asteroids, and comets in our own Solar System. In the future, stellar rendezvous starprobes could deposit similar robots on the worlds orbiting their target stars, and relay the robots’ findings to Earth.)
A network of such analog devices might also possibly (perhaps in combination with some digital subsystems—such devices are called hybrid computers) function together to form a type of STAR (Self-Testing And Repairing) computer, which could control interstellar spacecraft. Since about 1961, NASA’s Jet Propulsion Laboratory had conducted research on a digital STAR onboard computer, which later in that decade found favor for the planned four-spacecraft Grand Tour mission, for which a non-flight “study model” called TOPS (Thermoelectric Outer Planet Spacecraft) was built. [13, 14, and 15] Kenneth Gatland, and the Soviet engineer B. Volgin (as was mentioned on page 244 of the former’s book, Robot Explorers, see Reference 13), both discussed the need for interstellar spacecraft to have self-repairing computer systems that could also learn and make decisions for themselves. To ensure acceptable mission risks, the computer systems of interstellar probes (and of any robotic sub-probes that they might carry, in the case of some stellar rendezvous—or even “fly-through”—missions) would have to be able to repair themselves in some way, regardless of how rapidly or slowly the vehicles traveled. Fast starprobes would face more intense impact and erosion damage by high-velocity atoms and dust particles (and induced cosmic rays, at high relativistic speeds), while slow probes would be subjected to long-term bombardment by galactic cosmic rays during their decades-long or centuries-long journeys. Self-healing electronic components and STAR-type features appear to be promising solutions to ensure that the vehicles’ electronic brains would remain sharp during transit, and upon and after arrival.
Getting There—Practically and Affordably
Over the years, many interstellar probe concepts have been studied and advocated. Among the earliest ones were ion propulsion, which Soviet scientists discussed at the 1973 International Astronautical Congress in Baku, Azerbaijan. At that meeting, a paper written and endorsed by members of the USSR Academy of Sciences concluded that ion-drive starprobes using then-current technology were feasible. [16] They predicted a flight time of about four hundred years to Barnard’s Star (six light-years away), and a journey duration of six hundred years to stars approximately twelve light-years away. Elsewhere in the 1974 book that discusses the Soviet paper (Is Anyone Out There?, by Jack Stoneley with Anthony T. Lawton, see Reference 16), it is mentioned that ion-drive probe velocities of 5% of c, the speed of light, are possible. The researchers envisioned ion-drive probes about the size of a Saturn rocket, which would enter orbit around their target stars.
Nuclear pulse propulsion—using fission or fusion bombs, or laser- or electron beam-triggered fusion micro-explosions occurring at higher rates—has also been studied extensively. The designs of the Orion starship and the Project Daedalus starprobe (a 0.12 c stellar system fly-through probe) utilized both nuclear pulse methods. [17] While both the bomb-type (Orion) and the fusion micro-explosion-type (Daedalus) designs were enormous and extremely expensive, recent dramatic reductions in payload size and mass would make much smaller interstellar probes feasible. Dr. Mason Peck’s “Sprites”—chip-size spacecraft weighing just a few grams—could be accelerated to high interstellar transit velocities (and be decelerated for relatively slow flybys or circum-stellar orbit insertion) by much smaller propulsion systems. [18] In fact, a much smaller Daedalus-like starprobe could release dozens or even hundreds of Sprite probes, which could be targeted to fly by and examine all of the planets in the destination stellar system.
These tiny “spacecraft-on-a-chip” probes also make laser-pushed lightsails—and even solar sails—attractive as potential high-velocity propulsion systems. The Breakthrough Starshot lightsail starprobe project, and NASA’s notional 2069 0.1 c solar sail interstellar probe project (NASA is also considering other propulsion systems), have both become serious contenders thanks to Sprites. [19 and 20] Analyses of laser-pushed lightsails indicate that as the sail velocity approaches c, the beam’s effectiveness in imparting momentum to the sail falls sharply, because a visible light laser’s Doppler-shifted light descends to infrared frequencies (as the sail “sees” the beam’s light). [21, 22, and 23] For sail velocities of 0.1 – 0.2 c or so, these “wavelength-stretching” Doppler shift effects aren’t large enough to cause serious beam thrust drop-off.
G. Marx proposed a variation of the laser-pushed lightsail concept which could reduce the overall complexity and cost of such interstellar probes. [21] He pointed out that an X-ray laser located above the Earth’s atmosphere could emit a much more powerful collimated beam (for the same beam aperture) than an ultraviolet, visible light, or infrared laser. Since X-rays can only be reflected by grazing incidence (shallow-angle reflection) nickel reflectors (like those used in space-based X-ray imaging telescopes), an X-ray laser-pushed lightsail starprobe could be in the shape of a narrow cone of thin nickel foil, with the payload located in its rearward-facing tip. If spin stabilization proved necessary, the conical sail could have several spiral, ridged “flutes”—rather like the spirals depicted on a unicorn’s horn—running from its pointed tip to its base; the flutes would reflect some of the beam, imparting spin to the conical sail. Such X-ray lightsails could be quite small. A SETI “bonus,” for any aliens looking in our direction, would be that such an anomalous, directional X-ray laser beam emission coming from near our Sun should grab their attention (and vice-versa, if anyone out there launched X-ray laser-pushed lightsail starprobes—or starships—in our direction).
Sending slower probes would ease many of the challenges of designing such spacecraft, which would lower their unit cost and enable larger numbers of them to be launched. Cyril Ponnamperuma and A. G. W. Cameron pointed out that it would be extremely wasteful of economic and energy resources to design probes that would travel faster than 1 percent of the speed of light, advocating that technological resources should instead be devoted to ensuring that the probes would remain reliable for long periods. [24] At such a velocity, their propulsion requirements (including braking to enter circum-stellar orbits) and interstellar material (stray atoms and dust particles) erosion shielding requirements would be greatly reduced. Ronald Bracewell also supported this “longevity over speed” strategy, based on his conclusion that the closest spacing between civilizations was probably (except for rare, random close spacing) on the order of at least 100 light-years.
Such spacing would make radio and laser SETI searches problematic because we—and the nearest other technological civilization—would each have about 1,000 surrounding promising stars to check, yielding maximum odds of success of 1 in 1,000,000. The actual odds would be significantly lower than this due to both parties’ unavoidable complete ignorance of what frequencies to use, and when—and toward which star—each society was transmitting or listening at any time. These limitations led Bracewell to develop his interstellar messenger probe concept, which would avoid these problems (and would return data and images from all stellar systems visited—including those without resident intelligent life—making every probe mission scientifically worthwhile). He proposed that in order to examine their 1,000 closest stars, and to establish contact with intelligent beings found around any of them (or to at least inform the “seeking” planet of their existence), another technological civilization would dispatch 1,000 modest interstellar probes, launching at least one probe (and more, if finances permitted) per fiscal year. [25] Bracewell also suggested that humanity would one day engage in such interstellar exploration and SETI searches by means of starprobes. Frederick Ordway suggested that interstellar probes could also monitor for intelligent signals while in transit between the stars. [26]
The nanotechnology scientist Robert A. Freitas, Jr. also advocates the use of Bracewell probes, in a complementary fashion with traditional SETI searches. [27 and 28] Like Bracewell, he points out the relative insensitivity of a probe program’s effectiveness to interruptions in the probe launch rate (because probes already launched will continue with their missions). Freitas is also in favor of the development of self-replicating starprobes (Von Neumann probes), whose general principles were developed by the mathematician John Von Neumann. [29] While this is an economically and logistically attractive concept (because just a few probes, once launched, would multiply, at zero additional cost to the funding government), this approach has a potential ethical problem. Would an intelligent race—including our own—appreciate it if an alien spacecraft suddenly showed up and began harvesting the worlds of its stellar system to produce copies of itself? Its transmitted assurances that its purposes were entirely peaceful might ring very hollow. Also, the highly sophisticated technology that will be necessary for such self-replicating probes is nowhere near fruition. When we can build a device that—if set on the ground—can move around, find and process iron, and make tenpenny nails all by itself, there may be some hope for progress in this field; but even then, it must be remembered that even the simplest spacecraft are far more complex than carpentry nails.
Approach, Arrival, and Post-Arrival Activities
What terrestrial interstellar probes will do as they close in on their targets will depend not only on humanity’s technological capabilities, but also on economic and political considerations. These latter two factors are, of course, interdependent, and may be influenced by the probes’ transit times. (Modern-era governments are less enthusiastic about funding projects which will come to fruition long after the legislators involved are out of office, or even dead, and high-cost projects of this nature are even less popular among politicians.) Depending on the tradeoffs between these factors, interstellar probes may be either stellar system fly-through vehicles or stellar rendezvous (star-orbiting) spacecraft. While probes having cruise velocities of 10% – 20% of c would be more popular with the project scientists and enthusiasts, 1% of c probes would be considerably simpler and cheaper, and they would be less likely to meet premature ends due to in-transit debris impacts. From the point of view of the politicians who would appropriate the funding for the spacecraft, the difference between 0.1 c and 0.01 c probes would make little difference as far as their career durations were concerned, but the much lower price tag of each 0.01 c probe would be more attractive. Also, they could attract political merit by “investing in the future” and “voting to find new worlds for humanity to explore and, perhaps, discover other civilizations with whom we might one day communicate.”
Fly-through probes would be the least challenging in terms of size, complexity, propulsive capability requirements, and cost, while stellar rendezvous probes would be able to make more detailed observations of their target exoplanetary systems. Essentially immortal fly-through starprobes could also conduct “open-ended,” multi-target flyby missions, passing from star to star by utilizing stellar gravity assists to propel them. Such probes would be slow by human standards, as they moved in trajectories similar to those of comets that were ejected from stellar systems by encounters with gas giant planets. But in compensation, they would make leisurely passes through their destination stellar systems. This would give them time to examine the planets in some detail, and—if the probes were so equipped—to listen for intelligent electromagnetic signals and engage in communication with any “local aliens.” Ronald Bracewell initially advocated stellar rendezvous probes exclusively, but he later concluded that fly-through probes would also be sufficient for carrying out these functions. As David Darling wrote some years ago:
“More recently, Bracewell has suggested that it would be sufficient merely for a messenger probe to pass through a planetary system to achieve its goals (as in the case of Project Daedalus). Without the need for retrorockets, such a probe could be made smaller and at much lower cost. Our contribution to the success of attempts by alien races to establish contact in this way might be to construct a sophisticated space watch system, possibly an extension of one designed to search for Near-Earth Objects.” [30]
In his 1978 novel The Fountains of Paradise, Arthur C. Clarke described a stellar gravity assist-propelled, alien fly-through Bracewell probe called Starglider, which passed through the Solar System in 100 days after having been detected moving through the outer Solar System at six hundred kilometers per second. [31] Faster fly-through starprobes (particularly non-Bracewell ones intended only to examine stars and exoplanets) could make more rapid journeys, then slow down before arrival in order to conduct data-collecting and image-taking flybys.
A stellar rendezvous probe would require a greater delta-v capability, so that it could both accelerate to cruise velocity and later brake into orbit around its target star. Limiting such probes’ maximum velocity to 1% of the speed of light would reduce the amount of energy required for braking upon arrival. Ion or plasma propulsion could power the probes. Sail propulsion (using either a laser-pushed lightsail or a solar sail, with the latter utilizing a “Sun-diver” trajectory) could produce a departure velocity of 0.01 c, but braking into circum-stellar orbit upon arrival might limit the target list to multiple star systems (and only at certain times), where photo-gravitational braking could be used. An E-sail (Electric sail, which is pushed by solar wind or stellar wind ions) could also be employed for braking. One advantage of photon sails and E-sails for rendezvous starprobes is that after circum-stellar orbit capture, either type of sail would enable the spacecraft to change its orbit to visit interesting exoplanets in the system (especially in the star’s habitable zone), without expending any fuel.
The spin-rigidized E-sail could also potentially serve as a probe-to-Earth communications antenna and—in a Bracewell probe—as a signal-monitoring and (if local technological life was found) local communications antenna. An E-sail, which uses positively-charged wires to repel the positively-charged solar or stellar wind ions, can use any number of such wires, from one up to dozens (in a “wagon wheel” configuration). [32] The wires (which are typically kilometers in length) are many wavelengths long at the frequencies used by spacecraft radio systems. Extremely long—in terms of multiple wavelengths—wire antennas are highly directional. As the ARRL Antenna Book says (the American Radio Relay League is the governing body for amateur radio in the United States), “The longer the antenna, the sharper the lobe becomes, and since it is really a hollow cone of radiation about the wire in free space, it becomes sharper in all planes. Also, the greater the length, the smaller the angle with the wire at which the maximum radiation occurs.” [33]
In other words, as the antenna is made longer (increasing the frequency of the radio transmitter and/or receiver that is connected to the wire causes the same effect), the radio energy is concentrated and emitted more and more off the end of the antenna (and the receive pattern is identical to the transmit pattern, so that the antenna is most sensitive to signals arriving at its end). In Section 2.1 of his online article, “Small Smart Interstellar Probes,” Allen Tough suggested that a probe could trail a very thin antenna. [34] A spinning “wagon wheel” E-sail, if its spin axis was precessed so that the Earth was in or near the sail’s plane of rotation, could communicate with Earth by electronically selecting each wire in turn (in a multiplexed way), as its far end was pointed at the Earth at some point during each rotation (multiplexed antenna systems have long been in use). This same arrangement could be used in the destination stellar system, for radio science data collection and (if the vehicle was a Bracewell probe) to listen for and communicate with any intelligent inhabitants in the system. Used with a variable matching network, the E-sail’s long wires could serve as signal monitoring and transmitting antennas over very wide frequency ranges.
An often-expressed objection to non-relativistic interstellar spacecraft (as generally expressed, space vehicles that travel at 10% or less of the speed of light) is, “It wouldn’t be worthwhile to send such slow interstellar probes because no one a century or more from now would be interested in data from them.” The systematic collection of other, often far older data in science does not support this contention. Astronomers directly image Jovian-type exoplanets that are hundreds of light-years away, and have even measured their wind velocities via transits, and that is—by definition—*very* old data. (Old astronomical photographs, and even hand sketches in notebooks, are prized because they enable more precise orbits of celestial objects to be computed, and because they record changes in such objects’ brightness and/or physical characteristics over time.) Slow starprobes would tell us a lot while they were en route to their target stars, and after arrival they would have far more detailed instrument and imager views than what we could ever perceive from the distant Earth. Another example that runs counter to this assumption involves Pioneer 10 and 11 and Voyager 1 and 2; no space scientists ever suggested that they be turned off “because they’re too old and obsolete.” On the contrary, they were (Pioneer 10 & 11) and are (Voyager 1 & 2) treasured for reporting on conditions in remote regions of space, where no other on-site instruments are available (New Horizons will also be so valued, after its last encounter).
Stellar system fly-through and rendezvous probes would carry out planet and satellite observations similar to those of planetary flyby and orbiter probes in our Solar System, and they would also examine the stars (and any companion suns) in their target stellar systems. Fly-through probes would seek out and target (for close flybys) any planets orbiting in their destination stars’ habitable zones, as well as observe other planets as closely as possible. Slower fly-throughs would enable more opportunities to observe more planets at closer range. Stellar rendezvous probes could, after braking into orbit around their assigned stars, change orbits to investigate the various planets; sail-equipped probes could conduct such “extrasolar Grand Tour missions” (including comet-like outer planet flybys to return to the near-star regions) without using any propellant.
Seeking Neighbors and Making New Friends
Bracewell interstellar messenger probes (of either the fly-through or rendezvous type) would, in addition to exploring their target stellar systems, listen for any local artificially-produced electromagnetic (radio or laser) signals, then attempt contact if any such signals were detected. Ronald Bracewell developed a complete, language-independent contact and communication plan, which the probes could implement if they heard intelligently-produced signals. By merely receiving such signals, a probe would know that on that frequency, the planet’s atmosphere was transparent to the signals. It would also know that somewhere on the planet and/or in its vicinity, someone (and likely many someones) would be operating a receiver capable of receiving that frequency. Armed with this knowledge, the probe—an electronic ambassador of the human race—could get to work. [35]
Ronald Bracewell divided the problem of contact with technological life in the Milky Way into three categories—abundant, sparse, and rare life—in which our nearest neighbors would be less than 30, 30 to 300, or from 300 light-years to the edge of the galaxy away. (He also listed two special, extreme cases, in which humanity is alone in the galaxy, or alone in the universe). Being moderately pessimistic (or moderately optimistic, depending on one’s point of view), he surmised that the nearest technological society was probably no closer than 100 light-years (within his sparse life category), meaning that our search would be in a spherical volume of space containing 1,000 stars likely to possess habitable planets. With such a large number of possible stars for us—and for the nearest extraterrestrial civilization—to each search via radio and/or optical SETI methods (and they wouldn’t all be the same stars), the odds of both societies happening to cross electronic paths would be significantly less than one in a million. These unpromising odds led him to develop the interstellar messenger probe concept, which overcomes the geometrical (statistical), fiscal (the cost in time and money), and political (funding and operation interruptions due to wars, revolutions, or economic depressions) problems that could derail long-term SETI and METI programs. No matter what happened at home (short of extinction or “being bombed back to the Stone Age” events), the probes would be transmitting their findings and would, if necessary, be waiting to re-establish contact.
Before arrival at its destination star, each probe would locate the star’s equatorial plane, in (or near) which its planets orbit. (Imaging the star’s starspots and tracking their motion, or viewing the star’s zodiacal light dust plane with an occulting disc coronagraph, would enable the star’s equatorial plane to be found.) Upon entering the system, the probe would observe the planets and their moons, paying particular attention to any planets orbiting in the star’s habitable zone. (Once it was close enough to the star, the probe could supplement its onboard power with stellar power collected via photovoltaic cells, thermocouples, or perhaps Stirling cycle generators.) If any such planets were present, the probe would enter orbit around the star in the habitable zone (or if it was a fly-through probe, it would adjust its velocity and course to ensure a slow pass through the system). If its monitoring revealed any artificial radio (or perhaps laser) signals, the probe would announce its presence by retransmitting portions of the signals back to their source, at the same frequency on which it received them. Anyone listening to (or watching, if the signals were video) the original signals would detect what seemed to be a strong echo, whose delay (of seconds to minutes, depending on the probe’s distance from the planet) would be twice the time required for the signal to go out to the probe. Such an odd effect would attract the attention of whoever was receiving the original signals, and radio direction-finding techniques would immediately show that the echo was coming from a point out in space. Not long after that, its orbit should be roughly known.
If such beings were intelligent enough to have radio, they should also be clever enough to signal to the probe that they know it is there, by changing their transmission to short phrases separated by quiet intervals in order to remove any overlap of each phrase and its echo. The probe would then detect that the character of the transmission had changed radically to one that was periodic, with a period which would indicate that the probe itself was influencing the distant transmitter. By promptly ceasing to echo, the probe could signal to its new neighbors that it knew that they knew it was there. In other words, both parties would then be aware of each other, and that each party was aware that the other knew of its presence. Once this milestone was reached, events could unfold in multiple ways.
The operator of the transmitter might be under some pressure to persuade the probe to change its frequency, so that the transmitter’s normal function could resume. But desiring to avoid losing this first precarious contact, the probe—which would have the initiative, yet would know very little about the capabilities of the aliens’ radio technology—might begin to test the capabilities of their radio equipment. Without understanding a word (or its equivalent) of their language (and vice-versa), the probe could discover technical parameters such as how sensitive their equipment was, its bandwidth capability (how fast they could receive), and whether another frequency would be more convenient (for technical or political reasons that the locals would know about, but which the probe wouldn’t). The probe would also need to ensure that its message wouldn’t be lost because it would sooner or later—due to the planet’s rotation—set below the horizon of its first contact. It might also have to be prepared for local phenomena (afternoon thunderstorms, sandstorms, starspots, etc.) that could interrupt radio communication.
To test the sensitivity of the aliens’ equipment it could simply weaken its echo. Each time they responded, the probe would weaken its reply, until its signal level dropped low enough that clear reception was difficult, after which the aliens—who could no longer “read” the probe’s signal—would cease to repeat. Having gathered this information, the probe would bring its transmission power back up to its normal level. It would then shift its frequency slightly, which the aliens (if that particular set of radio gear could do it) would follow, and then—if they were able to follow—it would shift its frequency a little more. (Ronald Bracewell noted that if an alien probe happened to first make contact with a commercial radio or television station on Earth, its operators would have great difficulty following the probe’s frequency shifts, but that as soon as a variable-frequency transmitter was brought into action, we could take the lead in changing the frequency slightly, to lead the probe off to another frequency that would be more convenient to us.) By slowly shifting its frequency (both up and down), the probe could also determine the frequency “windows” of the planet’s atmosphere (that is, at what frequencies the atmosphere was transparent to radio waves).
Bracewell also considered the possible political implications of a probe making contact with an alien civilization, if the civilization of the planet in question had any degree of sociopolitical similarity to ours. Unless that world had global political, social, and/or cultural unity, any given “nation” (perhaps even of a different species or subspecies on the planet) might desire to enter into exclusive relations with a probe, for reasons of prestige or possible economic or military advantage (from using the probe’s knowledge and/or technology). The probe’s message (and its mere existence) would likely be disturbing to the planet’s inhabitants, so it would have to be resourceful in order to avoid being trapped into secrecy, to avoid exclusive relations with one power (which would invite an attack by a rival power), and to avoid having its signal jammed by a minor power. The very nature of the probe’s movements, however, would tend to encourage a degree of cooperation between even rival powers, because the probe would set below any station’s horizon within hours. Also, the probe could identify any planet-wide entity (if there was one), to which it could transmit its message. It could simply reduce its transmission power level until respondents lacking large antennas, sensitive receivers, and planet-wide interconnection dropped out; the probe would deal with any organization(s) (analogous to NASA and its Earth-wide communications capabilities) that remained. If some power insisted on communicating with the probe independently, the planet-wide entity would have to defer to that nation for part of each day, or invite jamming for refusing to defer.
Bracewell envisioned that the probe’s message would be in the form of a television broadcast, because TV is like sign language. Geometrical shapes provide a way for two people who don’t understand each other’s languages to learn them. If technological intelligent alien beings have sight similar to ours (this seems likely), they probably have some form of television, and it could be utilized to foster mutual understanding. He pointed out that the number of words in the dictionary that can be defined by drawings probably runs into the thousands, and that many more could be defined by animated drawings. Not only nouns, but many verbs, adjectives, and adverbs can be depicted via television. Other words are harder to define in this way, but given such a “vidioctionary” that defined a few thousand basic words using still and animated pictures, it would be possible to interpret at least some of the more difficult ones.
Until common linguistic understanding was established between the probe and its new neighbors, television would also enable them to learn the answers to basic questions of importance, such as where the probe came from. The probe would first reach a television format in common with that of the aliens. This could be done by repeating its message until they worked out the probe’s TV format and repeated it back to the probe, or the probe could simply adopt their format, transmitting images of simple mathematical shapes (circles, squares, etc.); they could repeat the signal back to tell the probe, “You’ve got our TV format right!” Once this was done, the probe’s message could be a “zoom movie” (using computer graphic imagery where necessary).
It could begin with a view of a constellation or a star field (calculated to appear as it would from their planet) that included our Sun, with the view quickly zooming in on the Sun. The view could then zoom in further until the Sun appeared as a substantial disc, with sunspots visible on it. From their motion (with other nearby—in the angular sense—stars visible in the frame), the Sun’s axis of rotation and the axis’ orientation in space would be shown. Closer zooming would show our Solar System, and at last the view would zoom in on the Earth. Supplementary animated plan views (which could come after a video tour of the Earth) could show the interrelationships between the rotational and orbital periods of the Earth, the Sun, the Moon, and the other planets. Such views would provide the relative rotational and orbital periods (but the aliens, once they knew which star the probe had come from, could determine the Sun’s “absolute” rotational period via spectroscopy, and—possibly—the Earth’s rotational period by monitoring terrestrial radio, TV, and radar emissions). A “zoom travelogue” of our home planet would show our newly-discovered neighbors our world, its natural beauty, its architecture, and views and voices of the beings—and their science, industry, and cultures—that created and launched the probe.
After this, the probe would have another, important piece of business to take care of—conveying the particulars (the frequency, listening schedule, etc.) of how the aliens could engage in direct radio (and/or laser) communication with the Earth. With multiple probes sent to as many stars, radio and/or laser communication telescopes on the Earth, the Moon, or in solar orbit would have to listen to the probes on a schedule, and blocks of time would also need to be allotted for receiving direct messages from any extrasolar civilizations discovered by the probes. (Any probe that found technological intelligent life could first send a report of the discovery to its Earthside controllers before attempting to contact the civilization—and probes that found no such life could also report their negative findings—as this would permit the most efficient use of the “listening time” blocks; such time periods need not be wastefully kept open for stars with no inhabited planets.) Bracewell believed—in the mid-1970s—that the direct interstellar communication information could be expressed by messenger probes using static and/or moving television images. With today’s vastly improved television and computer technologies, such information would likely be easier to convey effectively.
After this task was accomplished, the probe would be dispensable, although the aliens could learn much more about us (and vice-versa) through continued interaction with the probe, which could be packed with enormous quantities of information (even using today’s technology). If the probe met an untimely end, the aliens would have to transmit to the Earth a pictorial dictionary followed by their text or pictographs, and hope for the best. But assuming that the probe didn’t fail, it and they could learn each other’s languages, which would be most helpful for their direct transmissions to us. (The probe would have an “alien/Terran” language translation program, which the probe could send them a copy of on request.) The probe could readily learn their language in printed form, by utilizing an animated pictorial dictionary that they could transmit to it. Its first attempts to “talk” to them in their language might be quaint to them, but they could televise corrected versions back to it.
To be sure that it was properly understood, the probe could do what human beings do—say it again in different words. If they didn’t understand, they could question. (This is a huge advantage of real-time, quick-feedback loop communication with a local “resident” Bracewell probe; it facilitates rapid learning and understanding by both parties, as compared with very long-delay direct interstellar transmissions that take years, decades, or centuries each way). “Probe-mediated initial contact” would enable the direct interstellar transmissions between civilizations to be in mutually-understandable forms from the start. Knowledge of aliens’ languages would enable probes to exchange scientific (including medical and astronomical), philosophical, and cultural knowledge with them, and their races’ knowledge would, of course, immeasurably enrich our own civilization.
If we found even one other technological civilization, the messenger probe concept (which is tolerant of diversion of resources to urgent priorities, because interruption of the launching program does not affect in-flight probes’ chances of success) would enable our societies’ combined efforts to greatly enlarge the volume of galactic space in which more such societies could be sought out for contact. Our space program and theirs could, without wasteful overlap, dispatch messenger probes into large “bubbles” of unexplored space centered on our respective suns. But even if we are the only technological society for thousands—or tens of thousands—of light-years around, none of the Bracewell probes would be wasted, because they would return scientific data and images from the stellar systems they explored. (Even probes that failed to reach their destinations in functional condition would, if they operated well for several years, gather useful information on the interstellar medium, the galactic magnetic field, and cosmic rays in their regions of space.)
Launching interstellar messenger probes would be a “no-lose” (“win-win”) situation. Current and/or soon-to-be-in-hand technologies would likely be sufficient to produce and launch Bracewell probes, particularly ones designed to travel at 1% of the speed of light. (“Sun-diver” solar sails and large ion-drive spacecraft—Soviet scientists advocated the latter as starprobes in 1973, and wrote that they were feasible with then-current technology—could attain that velocity, given some engineering development work and flight testing; no new principles need to be discovered.) The “brains and senses” of Bracewell probes are probably already within our technological reach, at least in “breadboard” prototype form. Computers and software of the necessary sophistication to discriminate between natural radio noise and artificial signals—and to conduct the contact activities that Ronald Bracewell envisioned—already exist, as does the high-density information memory storage that such “electronic ambassadors” would require. The variable matching network-equipped, wideband-tunable longwire antenna and antenna multiplexing are both decades-old technology (which could be utilized if a braking E-sail’s wires were also used as probe-to-Earth, radio science, and alien signal-monitoring antennas; slowly rotating ion-drive starprobes could also use such antenna technology).
Sending realistically-realizable probes to other stars, even the nearest ones, will require patience. But even the fastest-possible (with foreseeable technology) ones, even if launched today, would not reach the Alpha Centauri system, let alone the considerably more distant potentially habitable stellar systems, within the lifetimes of most living adult interstellar spaceflight advocates. That is all the more reason to begin work on such ventures as soon as possible, so that—like trees planted by old men who knew they would never get to enjoy their shade—the first pictures and data from other stellar systems can inform and inspire the immediate descendants of our generation.
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[1] 1I/2017 U1 (‘Oumuamua) interstellar asteroid information, NASA Solar System Exploration website: http://solarsystem.nasa.gov/planets/oumuamua/indepth
[2] The Galactic Club: Intelligent Life in Outer Space by Ronald N. Bracewell, page 83 (Published 1974 and 1975 by W. H. Freeman and Company, San Francisco, CA, ISBN: 0-7167-0353-X and 0-7167-0352-1 pbk.) Amazon.com link: www.amazon.com/s/ref=nb_sb_noss?url=search-alias%3Dstripbooks&field-keywords=The+Galactic+Club+by+Ronald+Bracewell
[3] “Meteorites and Cosmic Radiation” by I. R. Cameron (Scientific American, Vol. 229, No. 1, page 65, July 1973)
[4] “Self-Healing Transistors for Chip-Scale Starships” (IEEE Spectrum, January 30, 2017): http://spectrum.ieee.org/semiconductors/devices/selfhealing-transistors-for-chipscale-starships
[5] Pioneer 6, 7, 8, and 9, Wikipedia article: http://en.wikipedia.org/wiki/Pioneer_6,_7,_8,_and_9
[6] LES 1 satellite, Google website citations.
[7] LES 8, 9, Gunter’s Space Page article: http://space.skyrocket.de/doc_sdat/les-8.htm
[8] Lincoln Experimental Satellite Turns 40, MIT Lincoln Laboratory website article: www.ll.mit.edu/news/LES-9-turns-40.html
[9] AMSAT-OSCAR 7, Wikipedia article: http://en.wikipedia.org/wiki/AMSAT-OSCAR_7
[10] International Cometary Explorer, Wikipedia article: http://en.wikipedia.org/wiki/International_Cometary_Explorer
[11] Morphic Resonance: The Nature of Formative Causation by Rupert Sheldrake, page 247 (4th Revision, Published 2009 by Park Street Press, Rochester, VT, ISBN: 978-1594773174 and 1594773173) Amazon.com link: www.amazon.com/Morphic-Resonance-Nature-Formative-Causation/dp/1594773173/ref=sr_1_1?ie=UTF8&qid=1520811667&sr=8-1&keywords=morphic+resonance+rupert+sheldrake
[12] “Redefining Robots” by P. Trachtman (Smithsonian Magazine, February 2000, pages 97 – 112)
[13] Robot Explorers by Kenneth Gatland, pages 239 – 244 (Published 1972 by Blandford Press, London, ISBN: 0-7137-0573-6) Amazon link: www.amazon.com/Robot-Explorers-Colour-Kenneth-Gatland/dp/0713705736/ref=sr_1_fkmr0_1?ie=UTF8&qid=1520817457&sr=8-1-fkmr0&keywords=robot+explorers+by+kenneth+garland
[14] Planetary Exploration: Space in the Seventies by William R. Corliss (NASA Publication EP-82, June 1971): http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19750065009.pdf
[15] Computers in Spaceflight: The NASA Experience by James E. Tomayko, pages 149 – 153 (NASA Contractor Report 182505, March 1988): http://history.nasa.gov/computers/Ch5-5.html
[16] Is Anyone Out There? by Jack Stoneley with Anthony T. Lawton, pages 15, 17, and 174 (Published 1974 by Warner Paperback Library, New York, NY) Amazon link: www.amazon.com/Anyone-Out-There-Jack-STONELEY/dp/0446765740/ref=sr_1_1?s=books&ie=UTF8&qid=1522566430&sr=1-1&keywords=Is+Anyone+Out+There%3F+by+Jack+Stoneley
[17] Nuclear pulse propulsion, Wikipedia article: http://en.wikipedia.org/wiki/Nuclear_pulse_propulsion
[18] “Sprites: A Chip-Sized Spacecraft Solution” (Centauri Dreams, July 17, 2014): www.centauri-dreams.org/2014/07/17/sprites-a-chip-sized-spacecraft-solution/
[19] Breakthrough Starshot, Breakthrough Initiatives website: http://breakthroughinitiatives.org/initiative/3
[20] NASA 2069 Alpha Centauri solar sail probe, Google website citations.
[21] “Interstellar Vehicle Propelled by Terrestrial Laser Beam” by G. Marx (Nature, Vol. 211, July 1966, pages 22 – 24)
[22] “Interstellar Vehicle Propelled by Terrestrial Laser Beam” by J. L. Redding (Nature, Vol. 213, February 1967, pages 588 – 589)
[23] “Was Marx right? Or how efficient are laser driven interstellar spacecraft?” by J. F. L. Simmons and Colin R. McInnes (American Journal of Physics, Vol. 61 (1993), pages 205 – 207)
[24] Interstellar Communication: Scientific Perspectives by Cyril Ponnamperuma and A. G. W. Cameron, page 100 (Published 1974 by Houghton Mifflin Company, Boston, MA, Library of Congress Catalog Card Number: 73-11945, ISBN: 0-395-17809-6) Amazon link: www.amazon.com/Interstellar-Communication-Perspectives-Cyril-Ponnamperuma/dp/0395178096/ref=sr_1_1?s=books&ie=UTF8&qid=1522566770&sr=1-1&keywords=Interstellar+Communication%3A+Scientific+Perspectives+by+Cyril+Ponnamperuma
[25] “Transcription of the Lectures of Ronald Bracewell on the Studies of Extraterrestrial Life” (Stanford Alumni Conference Lecture, delivered on June 1, 1974, pages 16 and 17 [this transcript is available by e-mail from the author at: blackshire@alaska.net]).
[26] Life in Other Solar Systems by Frederick I. Ordway, III, pages 78 and 79 (Published 1965 by E. P. Dutton & Co., Inc., New York, NY, Library of Congress Catalog Card Number: 65-12184) AbeBooks link: http://www.abebooks.com/servlet/SearchResults?sts=t&cm_sp=SearchF-_-home-_-Results&an=Ordway%2C+Frederick&tn=Life+in+Other+Solar+Systems&kn=&isbn
[27] “Interstellar Probes: A New Approach to SETI” by Robert A. Freitas, Jr. (Journal of the British Interplanetary Society, Vol. 33, pp. 95-100, 1980): http://www.rfreitas.com/Astro/InterstellarProbesJBIS1980.htm
[28] “The Case for Interstellar Probes” by Robert A. Freitas, Jr. (Journal of the British Interplanetary Society 36:490-495, November, 1983): http://www.rfreitas.com/Astro/TheCaseForInterstellarProbes1983.htm
[29] Self-replicating spacecraft, Wikipedia article: http://en.wikipedia.org/wiki/Self-replicating_spacecraft
[30] Bracewell probes, The Worlds of David Darling website article: http://www.daviddarling.info/encyclopedia/B/Bracewellprobes.html
[31] The Fountains of Paradise by Arthur C. Clarke (Various hardcover, paperback, audio, and e-book editions, first published 1978) Amazon link: www.amazon.com/Fountains-Paradise-S-F-Masterworks/dp/1857987217/ref=sr_1_1?s=books&ie=UTF8&qid=1520817523&sr=1-1&keywords=the+fountains+of+paradise+by+arthur+c.+clarke
[32] Electric sail, Wikipedia article: http://en.wikipedia.org/wiki/Electric_sail
[33] ARRL Antenna Book, pages 13-1 and 13-2 in Chapter 13, “Long Wire and Traveling Wave Antennas” (Published at intervals by the American Radio Relay League, Newington, CT): http://www.qrz.ru/schemes/contribute/arrl/chap13.pdf
[34] Small Smart Interstellar Probes (Section 2.1), Professor Allen Tough’s website: http://ieti.org/tough/articles/8.htm
[35] The Galactic Club: Intelligent Life in Outer Space by Ronald N. Bracewell, pages 59 – 83 (Published 1974 and 1975 by W. H. Freeman and Company, San Francisco, CA, ISBN: 0-7167-0353-X and 0-7167-0352-1 pbk.) Amazon.com link: www.amazon.com/s/ref=nb_sb_noss?url=search-alias%3Dstripbooks&field-keywords=The+Galactic+Club+by+Ronald+Bracewell
