What’s going on on the floor of Europa’s ocean? It’s hard to imagine a place like this, crushed under the pressure of 100 kilometers or more of water, utterly dark, although I have to say that James Cambias does wonders with an ice moon ocean in his novel A Darkling Sea (Tor, 2014). Science fiction aside, Europa Clipper is in queue for a 2024 launch, and we can anticipate a flurry of new studies that feed into plans for the mission’s scientific investigations. The latest of these puts Clipper on volcano watch. The work deploys computer modeling to show that volcanic activity seems to have occurred recently on Europa’s seafloor. The concept is that there may be enough internal heat to cause melting -- at least in spots -- of the rocky interior, which would produce the needed results. How this heating affects the moon is deduced from the 3D modeling of heat production and transfer in the paper, which was recently published in Geophysical Research Letters. The lead author is Marie...

On the matter of city lights as technosignatures, which we looked at on Friday, I want to follow up with Thomas Beatty's work on the issue in the context of an assortment of nearby stars. Beatty (University of Arizona, Tucson) assumes Earth-like planets examined via direct-imaging by LUVOIR, a future space telescope in planning, or HabEx, a different architecture for a likewise powerful instrument. What he's done is to take data from the Soumi National Polar-orbiting Partnership satellite to find the flux from city lights and the spectra of currently available lighting. He goes on to model the spectral energy distribution from such emissions as applied to exoplanet settings at various distances. Why look at city lights in the first place? Because they're another form of technosignature that may be within the realm of detection, and we'd like to find out what's possible and what any results would imply. In particular, Beatty reminds us, the National Academies' Exoplanet Science...

Our recent look at the possibility of technosignatures at Alpha Centauri is now supplemented with a new study on the detectability of artificial lights on Proxima Centauri b. The planet is in the habitable zone, roughly similar in mass to the Earth, and of course, it orbits the nearest star, making it a world we can hope to learn a great deal more about as new instruments come online. The James Webb Space Telescope is certainly one of these, but the new work also points to LUVOIR (Large UV/Optical/IR Surveyor), a multi-wavelength space-based observatory with possible launch in 2035. Authors Elisa Tabor (Stanford University) and Avi Loeb (Harvard) point out that a (presumably) tidally locked planet with a permanent nightside would need artificial lighting to support a technological culture. As we saw in Brian Lacki’s presentation at Breakthrough Discuss (see Alpha Centauri and the Search for Technosignatures), coincident epochs for civilizations developing around neighboring stars are...

Jim Benford's study of 'lurkers' -- possibly ancient probes that may have been placed here by extraterrestrial civilizations to monitor our planet's development -- breaks into two parts. The first, published Friday, considered stars passing near our Sun in the lifetime of the Solar System. Today Dr. Benford looks at the Drake Equation and sets about modifying it to include the lurker possibility. Along the way, he develops a quantitative way to compare conventional SETI with the strategy called SETA -- the search for extraterrestrial artifacts. Both articles draw on recently published work, the first in JBIS, the second in Astrobiology. The potential of SETA and the areas it offers advantages over traditional SETI argue for close observation of a number of targets close to home. by James Benford Introduction “To think in a disciplined way about what we may now be able to observe astronomically is a serious form of science.” –Freeman Dyson I propose a version of the Drake Equation for...

Jim Benford is continuing his research into the still nascent field known as SETA, the Search for Extraterrestrial Artifacts. A plasma physicist and CEO of Microwave Sciences, as well as a frequent Centauri Dreams contributor, Benford became intrigued with recent discoveries about Earth co-orbital objects -- there is even a known Earth Trojan -- and their possibilities in a SETI context. If we accept the possibility that an extraterrestrial civilization may at some point in Earth’s 4.5 billion year history have visited the Solar System, where might we find evidence of it? Two papers grew out of this, one in Astrobiology, the other in the Journal of the British Interplanetary Society (citations below). In the first of two posts here, Jim explains where his work has led him and goes through the thinking behind these recent contributions. by James Benford Part 1: How Many Alien Probes Could Have Come From Stars Passing By Earth? 1. Searching for Extraterrestrial Artifacts Alien...

Just how useful is oxygen as a biosignature? It’s a question we’ve examined before, always with the cautionary note that there are non-biological mechanisms for producing oxygen which could make any detected biosignature ambiguous. But let’s go deeper into this, thanks to a new paper on ‘oxygen false positives’ out of the University of California at Santa Cruz. The paper, produced by lead author Joshua Krissansen-Totton and team, offers scenarios that can place an oxygen detection in the broader context that would distinguish any such find as biological. Let’s begin with the fact that in addition to its obvious interest because of Earth’s history, photosynthesis involving oxygen requires the likely ubiquitous carbon dioxide and water we would expect on habitable zone planets. Helpfully, oxygen should be readily detectable on exoplanets because of its absorption features, which are prominent not only in visible light but in the near infrared and thermal infrared, if we include ozone....

Interesting news out of CNRS (the French National Center for Scientific Research) renews our attention to the mechanisms for supplying the early Earth with water and carbonaceous molecules. We've looked at comets as possible water sources for a world forming well inside the snow line, and asteroids as well. What the CNRS work reminds us is that micrometeorites also play a role. In fact, according to the paper just out in Earth and Planetary Science Letters, 5,200 tons of extraterrestrial materials -- dust particles from space -- reach the ground yearly. Image: From the paper's Figure 1, although not the complete figure. The relevant part of the caption: Fig. 1. Left: Location of the CONCORDIA station (Dome C, Antarctica). Centre: View of a trench at Dome C. Credit: Rojas et al. This conclusion comes from a study spanning almost twenty years, conducted by scientists in an international collaboration involving laboratories in France, the United States and the United Kingdom. CNRS...

Let's take a look at how Earth's carbon came to be here, through the medium of two new papers. This is a process most scientists have assumed involved molecules in the original solar nebula that wound up on our world through accretion as the gases cooled and the carbon molecules precipitated. But the first of the papers (both by the same team, though with different lead authors) points out that gas molecules carrying carbon won't do the trick. When carbon vaporizes, it does not condense back into a solid, and that calls for some explanation. University of Michigan scientist Jie Li is lead author of the first paper, which appears in Science Advances. The analysis here says that carbon in the form of organic molecules produces much more volatile species when it is vaporized, and demands low temperatures to form solids. Moreover, says Li, it does not condense back into organic form. "The condensation model has been widely used for decades. It assumes that during the formation of the...

I've used the discovery of 'Oumuamua as a learning opportunity. I knew nothing about the Local Standard of Rest (LSR) when the analysis of the object began, but soon learned that it measured the mean motion of interstellar materials in the Milky Way near the Sun. The Sun moves clockwise as viewed from galactic north, with an orbital speed that has been measured, through interferometric techniques, at 255.2 kilometers per second, give or take 5.1 km/s. Invoking the LSR in this connection calls for a quote from Eric Mamajek (JPL/Caltech) in his paper "Kinematics of the Interstellar Vagabond 1I/'Oumuamua (A/2017 U1)" (abstract here): 'Oumuamua's velocity is within 5 km/s of the median Galactic velocity of the stars in the solar neighborhood (<25 pc), and within 2 km/s of the mean velocity of the local M dwarfs. Its velocity appears to be statistically "too" typical for a body whose velocity was drawn from the Galactic velocity distribution of the local stars (i.e. less than 1 in 500...

I’m only just getting to Steven Desch and Alan Jackson’s two papers on ‘Oumuamua, though in a just world (where I could clone myself and work on multiple stories simultaneously) I would have written them up sooner. Following Avi Loeb’s book on ‘Oumuamua, the interstellar object has been in the news more than ever, and the challenge it throws out by its odd behavior has these two astrophysicists, both at Arizona State, homing in on a possible solution. No extraterrestrial technologies in this view, but rather an unusual object made of nitrogen ice, common in the outer Solar System and likely to be similarly distributed in other systems. Think of it as a shard of a planet like Pluto, where nitrogen ice is ubiquitous. Desch and Jackson calculated the object’s albedo, or reflectivity, with the idea in mind, realizing that the ice would be more reflective than astronomers had assumed ‘Oumuamua was, and thus it could be smaller. As the authors note: “Its brightness would be consistent with...

Given that we are just emerging as a spacefaring species, it seems reasonable to think that any civilizations we are able to detect will be considerably more advanced -- in terms of technology, at least -- than ourselves. But just how advanced can a civilization become before it does irreparable damage to itself and disappears? This question of longevity appears as a factor in the famous Drake Equation and continues to bedevil SETI speculation today. In a paper in process at The Astronomical Journal, Amedeo Balbi (Università degli Studi di Roma “Tor Vergata”) and Milan ?irkovi? (Astronomical Observatory of Belgrade) explore the longevity question and create a technosignature classification scheme that takes it into account. Here we’re considering the kinds of civilization that might be detected and the most likely strategies for success in the technosignature hunt. The ambiguity in Drake’s factor L is embedded in its definition as the average length of a civilization’s communication...

Héctor Socas-Navarro (Instituto de Astrofísica de Canarias) is lead author of a paper on technosignatures that commands attention. Drawing on work presented at the TechnoClimes 2020 virtual meeting, under the auspices of NASA at the Blue Marble Space Institute of Science in Seattle, the paper pulls together a number of concepts for technosignature detection. Blue Marble’s Jacob Haqq-Misra is a co-author, as is James Benford (Microwave Sciences), Jason Wright (Pennsylvania State) and Ravi Kopparapu (NASA GSFC), all major figures in the field, but the paper also draws on the collected thinking of the TechnoClimes workshop participants. We’ve already looked at a number of technosignature possibilities in these pages, so let me look for commonalities as we begin, beyond simply listing possibilities, to point toward a research agenda, something that NASA clearly had in mind for the TechnoClimes meeting. The first thing to say is that technosignature work is nicely embedded within more...

The reaction to Avi Loeb's new book Extraterrestrial (Houghton Mifflin Harcourt, 2021) has been quick in coming and dual in nature. I'm seeing a certain animus being directed at the author in social media venues frequented by scientists, not so much for suggesting the possibility that 'Oumuamua is an extraterrestrial technological artifact, but for triggering a wave of misleading articles in the press. The latter, that second half of the dual reaction, has certainly been widespread and, I have to agree with the critics, often uninformed. Image credit: Kris Snibbe/Harvard file photo. But let's try to untangle this. Because my various software Net-sweepers collect most everything that washes up on 'Oumuamua, I'm seeing stark headlines such as "Why Are We So Afraid of Extraterrestrials," or "When Will We Get Serious about ET?" I'm making those particular headlines up, but they catch the gist of many of the stories I've seen. I can see why some of the scientists who spend their working...

While we often think about so-called Dysonian SETI, which looks for signatures of technology in our astronomical data, as a search for Dyson spheres, the parameter space it defines is getting to be quite wide. A technosignature has to be both observable as well as unique, to distinguish it from natural phenomena. Scientists working this aspect of SETI have considered not just waste heat (a number of searches for distinctive infrared signatures of Dyson spheres have been run), but also artificial illumination, technological features on planetary surfaces, artifacts not associated with a planet, stellar pollution and megastructures. Thus the classic Dyson sphere, a star enclosed by a swarm or even shell of technologies to take maximum advantage of its output, is only one option for SETI research. As Ravi Kopparapu (NASA GSFC) and colleagues point out in an upcoming paper, we can also cross interestingly from biosignature searches to technosignatures by looking at planetary atmospheres....

The stars move ever on. What seems like a fixed distance due to the limitations of our own longevity morphs over time into an evolving maze of galactic orbits as stars draw closer to and then farther away from each other. If we were truly long-lived, we might ask why anyone would be in such a hurry to mount an expedition to Alpha Centauri. Right now we’d have to travel 4.2 light years to get to Proxima Centauri and its interesting habitable zone planet. But 28,000 years from now, Alpha Centauri -- all three stars -- will have drawn to within 3.2 light years of us. But we can do a lot better than that. Gliese 710 is an M-dwarf about 64 light years away in the constellation Serpens Cauda. For the patient among us, it will move in about 1.3 million years to within 14,000 AU, placing it well within the Oort Cloud and making it an obvious candidate for worst cometary orbit disruptor of all time. But read on. Stars have come much closer than this. [Addendum: A reader points out that some...

Moore’s Law, first stated all the way back in 1965, came out of Gordon Moore’s observation that the number of transistors per silicon chip was doubling every year (it would later be revised to doubling every 18-24 months). While it’s been cited countless times to explain our exponential growth in computation, Greg Laughlin, Fred Adams and team, whose work we discussed in the last post, focus not on Moore’ Law but a less publicly visible statement known as Landauer’s Principle. Drawing from Rolf Landauer’s work at IBM, the 1961 equation defines the lower limits for energy consumption in computation. You can find the equation here, or in the Laughlin/Adams paper cited below, where the authors note that for an operating temperature of 300 K (a fine summer day on Earth), the maximum efficiency of bit operations per erg is 3.5 x 1013. As we saw in the last post, a computational energy crisis emerges when exponentially increasing power requirements for computing exceed the total power...

I see there's now a Wikipedia page for BLC-1, the intriguing SETI detection made by Breakthrough Listen at the Parkes Observatory in Australia. The dataset in which the signal, found at 982 MHz, turned up comes from observations made in April and May of 2019, and it's good to know that Breakthrough is working up two papers on the signal and subsequent analysis, given that the public face of the detection was originally in the form of a story leaked to the British newspaper The Guardian before the backup research was available. Image: CSIRO's Parkes radio telescope in New South Wales, Australia. Credit: Shaun Amy. The first thing to say about BLC-1 is that the acronym stands for Breakthrough Listen Candidate 1, marking the first time a signal has made it through to actual 'candidate' status after five years of observations, which is itself noteworthy given the intensity of the effort. The second thing is that this is a transient, meaning it's short-lived, and it hasn't repeated. That...

Sorry for the server problems the last few days, which resulted in some tinkering under the hood by people far more skilled at such things than I am. Meanwhile, those experiencing deja vu at seeing this post should take heart -- there is a simple explanation. Last week I posted an earlier article about Claudio Maccone's upcoming presentation on gravitational lensing and the FOCAL mission to exploit it, but had to withdraw the post when I realized the live session, a 'webinar' organized by Ravi Kumar Kopparapu (NASA GSFC) and Jacob Haqq Misra (Blue Marble Space Institute of Science), might not be available beyond a restricted audience. Once that was straightened out, the meeting had already occurred, but fortunately Dr. Maccone's session was recorded and is now available here. I'm going to go ahead and run the rest of that earlier post now, because most people didn't see it. Even so, and despite the fact that it was only up on the site for a few minutes, that turned out to be long...

If we ever make a SETI detection, will it be of biological beings or machine intelligence? As Alex Tolley explains in today's essay, there are reasons for favoring the latter possibility, leading our author to compose what he calls a 'light-hearted speculation' about machines searching for other civilizations of their own kind. Life seems to be easy compared to this. We are developing the tools to delve into planetary atmospheres in search of biosignatures, hoping to cull out ambiguities. But is there an equivalent in the machine world of a biosignature, and how would it be found? Interesting implications arise, some of them seemingly close to home. by Alex Tolley Curiosity Rover. Credit Nasa. Terry Bisson's amusing short sci-fi story "They're made Out of Meat" [4], is a communication between two individuals who express their disbelief that a biological species (detected on Earth by a galactic survey) can possibly be intelligent. The denouement is to erase the record of discovery...

Science fiction writers range freely through time, making many scientific papers fertile ground for plot ideas and settings. So here's an extraordinary one. We know that Earth's continents used to be packed into a single large land mass called Pangaea, which is thought to have broken apart about 200 million years ago as tectonic plates shifted. Interestingly, we can expect a remote future in which the continents will have once again come together, as Michael Way (NASA GSFC) has pointed out at an online poster session at the ongoing virtual meeting of the American Geophysical Union. And such a supercontinent has ramifications for habitability. Let's talk about those because they have a bearing on astrobiology as we examine exoplanets and consider their suitability for life. We're a decade or so (at minimum) away from being able to determine how land and sea are distributed on a nearby world, but climate modeling is useful as we look toward estimating habitability. That involves, as...