I’ve maintained for years that the first discovery of life beyond Earth, assuming we make one, will be in an extrasolar planetary system, through close and eventually unambiguous analysis of an exoplanet’s atmosphere. But Alex Tolley has other thoughts. In the essay below, he looks at a privately funded plan to send multiple probes into the clouds of Venus in search of organisms that can survive the dire conditions there. And while missions this close to home don’t usually occupy us because of Centauri Dreams’ deep space focus, Venus is emerging as a prominent exception, given recent findings about anomalous chemistry in its atmosphere. Are the clouds of Venus concealing an ecosystem this close to home?
by Alex Tolley
Introduction
The discovery of phosphine (PH3), an almost unambiguous biosignature on Earth, in the clouds of Venus in 2021 increased interest in reinvestigating the planet’s clouds for life, a scientific goal that had been on hiatus since the last atmospheric entry and lander vehicle mission, Vega-2 in 1984. While the recent primary target for life discovery has been Mars, whether extinct, or extant in the subsurface, it has taken nearly half a century since the Viking landers to once again look directly for Martian life with the Perseverance rover.
However, if the PH3 discovery is real (and it is supported by a reanalysis of the Pioneer Venus probe data), then maybe we have been looking at the wrong planet. The temperate zone in the Venusian clouds is the nearest habitable zone to Earth. If life does exist there [see Figure 1] despite the presence of concentrated sulfuric acid (H2SO4), then it is likely to be in this temperate zone layer, having evolved to live in such conditions.
Figure 1. Schematic of Venus’ atmosphere. The cloud cover on Venus is permanent and continuous, with the middle and lower cloud layers at temperatures that are suitable for life. The clouds extend from altitudes of approximately 48 km to 70 km. Credit: J Petkowska.
But why launch a private mission, rather than leave it to a well-funded, national one?
National space agencies haven’t been totally idle. There are four planned missions, two by NASA (DAVINCI+, VERITAS), one by ESA (EnVision) to investigate Venus, all due to be launched around 2030, as well a Russian one (Venera-D) to be launched at the same time:
VERITAS and DAVINCI+ are both Discovery-class missions. They are budgeted up to $500 million each. EnVision is ESA’s mission launching in the same timeframe. All three missions have target launch dates ranging from 2028 (DAVINCI+, VERITAS) to 2031 (EnVision). As with any large budget mission, these missions have taken a long time to develop. DAVINCI was proposed in 2015, the revised DAVINCI+ proposed again in 2019, and selected in 2021 for a 2028 launch. VERITAS was proposed in 2015, and selected only in 2021. Then there is the seven years of development, testing, and finally launch in 2028. EnVision was selected in 2021, and faces a decade before launch.[5,6,7].
DAVINCI+’s goals include:
1. Understanding the evolution of the atmosphere
2. Investigating the possibility of an early ocean
3. Returning high resolution images of the geology to determine if plate tectonics ever existed.
[PG note: NASA GSFC just posted a helpful overview of this mission.]
Image: The Deep Atmosphere Venus Investigation of Noble gases, Chemistry, and Imaging (DAVINCI) mission, which will descend through the layered Venus atmosphere to the surface of the planet in mid-2031. DAVINCI is the first mission to study Venus using both spacecraft flybys and a descent probe. Credit: NASA.
VERITAS’s rather similar goals involve answering these questions:
1. How has the geology of Venus evolved over time?
2. What geologic processes are currently operating on it?
3. Has water been present on or near its surface?
EnVision’s goals include:
1. Determining the level and nature of current activity
2. Determining the sequence of geological events that generated its range of surface features
3. Assessing whether Venus once had oceans or was hospitable for life
4. Understanding the organizing geodynamic framework that controls the release of internal heat over the history of the planet
In addition, Russia has the Venera-D mission planned for a 2029 launch that has a lander. One of its goals is to analyze the chemical composition of the cloud aerosols. [8]
There is considerable overlap in the science goals of the four missions, and notably none have the search for life as a science goal, although the 3rd EnVision science goal could be the preparatory “follow the water” approach before a follow-up mission to search for life if there is evidence that Venus did once have oceans.
As with the Mars missions post Viking up to Perseverance, none of these missions is intended to look directly for life itself. Given the 2021 selection date for all three missions and the end of decade launch dates, it will be somewhat frustrating for scientists interested in searching for life on Venus.
Cutting through the slow progress of the national missions, the privately funded Venus Life Finder mission aims to start the search directly. The mission to look for life is focused on small instruments and a low-cost launcher. Not just one but a series of missions is planned, each increasing in capability. The first is intended to launch in 2023, and if the three anticipated missions are successful, Venus Life Finder would scoop the big science missions in being the first to detect life in Venus should it exist.
Some history of our views about Venus
Before the space age, both Venus and Mars were thought to have life. Mars stood out because of the seasonal dark areas and Schiaparelli’s observation of channels, followed by Lowell’s interpretation of these channels as canals, which carried the implication of intelligence. Von Braun’s “Mars Projekt” (1952) inferred that the atmosphere was thin, but the astronauts would just need O2 masks, and his technical tale had the astronauts discover an advanced Martian civilization. The popular science book “The Exploration of Mars” (1956) written by Willy Ley and Wernher Von Braun and illustrated by Chesley Bonestell, supported the idea of Martian vegetation, speculating that it was likely to be something along the lines of hardy terrestrial lichens.
Unlike Mars, the surface of Venus was not observable, just the dense permanent cloud cover. It was believed that Venus was younger than Earth and that the clouds covered a primeval swamp full of animals like those in our planet’s past. With the many probes starting in 1962 with the successful flyby of Mariner 2, it was determined that the surface of Venus was a hellish 438-482 C (820-900 degrees F), by far the hottest place in the Solar System. Worse, the clouds were not water as on Earth, but H2SO4, in a concentration that would rapidly destroy terrestrial life. Seemingly Venus was lifeless.
Some scientists thought Venus was much more Earth Like in the past, and that a runaway greenhouse state accounted for its current condition. If Venus was more Earth Like, there could have been oceans, and with them, life. On Earth, bacteria are carried up from the surface by air currents and have been found living in clouds and are part of the cloud formation process. Bacteria have been found in Earth’s stratosphere too. Bacteria living in the Venusian oceans would likely have been carried up into the atmosphere and occupy a similar habitat. If so, it has been hypothesized that bacterial life may have evolved to live in the increasingly acidic Venusian clouds just as terrestrial extreme acidophiles have evolved, and that this life is the source of the detected PH3.
The First Science Instrument
Is there any other evidence for life on Venus? Using two instruments, a particle size spectrometer and a nephelometer, the Pioneer Venus probe (1978) suggested that some tiny droplets in the clouds were not spherical, as physics would predict, and therefore might be living [unicellular] organisms.
But these probes could not resolve some anomalies of the Venusian atmosphere that might as a whole, indicate life.
1. Anomalous UV Absorber – spatial and temporal variability reminiscent of algal blooms.
2. Non-spherical large droplets – possible cells
3. Non-volatile elements such as phosphorus that could reduce the H2SO4 concentration and a required element of terrestrial life
4. Gases in disequilibrium, including PH3, NH3
Enter the Venus Life Finder (VLF) team, led by Principal Investigator Sara Seager, whose team includes the noted Venus expert David Grinspoon. The project isfunded by Breakthrough Initiatives. The initial idea was to do some laboratory experiments to determine if the assumptions about possible life in the clouds were valid.
As the VLF document states up front:
The concept of life in the Venus clouds is not new, having been around for over half a century. What is new is the opportunity to search for life or signs of life directly in the Venus atmosphere with scientific instrumentation that is both significantly more technologically advanced and greatly miniaturized since the last direct in situ probes to Venus’ atmosphere in the 1980s.
The big objection to life in the Venusian clouds is their composition: extremely concentrated sulfuric acid. Any terrestrial organism subjected to the acid is dissolved. [There is a reason serial killers use this method to remove evidence of their victims!]
To check on the constraints of cloud conditions on potential life and the ability to detect organic molecules, the VLF team conducted some experiments that showed that:
1. Organic molecules will autofluoresce in up to 70% H2SO4. Therefore organic molecules are detectable in the Venusian cloud droplets.
2. Lipids will form micelles in up to 70% H2SO4 and are detectable. Cell membranes are therefore possible containers for biological processes.
3. Terrestrial macromolecules – proteins, sugars, and nucleic acids – all rapidly become denatured in H2SO4, ruling out false positives from terrestrial contamination
4. The Miller-Urey experiment will form organic molecules in H2SO4. Therefore abiogenesis of precursor molecules is also possible on Venus.
With these results, the team focused on building a single instrument to investigate both the shapes of particles and the presence of organic compounds. Non-spherical droplet shapes containing organic compounds would be a possible indication of life. This instrument, an Autofluorescing Nephelometer, is being developed from an existing instrument, as shown in figure 2.
Figure 2. Evolution of the Autofluorescing Nephelometer (AFN) from the Backscatter Cloud Probe (BCP) (left of arrow) to the Backscatter Cloud Probe with Polarization Detection (BCPD) (right of arrow). The BCPD is further evolved to the AFN by replacement of the BCPD laser with a UV source and addition of fluorescence-detection compatible optics.
All this in a package of just 1 kg to be carried in the atmosphere entry vehicle.
Reaching Venus
The VLF team has partnered with the New Space company Rocket Lab which is developing its Venus mission. The company has small launchers that are marketed to orbit tiny satellites for organizations that don’t want to use piggy-backed rides with other satellites as part of a large payload. Its Electron rocket launcher has so far racked up successes. The Electron can place up to 300kg in LEO.
For the Venus mission, the payload includes the Photon rocket to make the interplanetary flight and deliver a 20 kg Venus atmosphere entry probe that includes the 1 kg AFN science package. To reach Venus, the Photon rocket using bi-propellant generates the needed 4 km/s delta V. It employs multiple Oberth maneuvers in LEO to most efficiently raise the orbit’s apogee until it is on an escape trajectory to Venus. Travel time is several months.
The Electron rocket, the Photon rocket, and the entry probe are shown in the next three figures.
The photon rocket powers the cruise phase from LEO to Venus intercept. This rocket uses an unspecified hypergolic fuel and will carry the entry probe across the 60 million km trajectory of its 3-month Venus mission.
Figure 3a. Electron small launch vehicle. The Electron ELV has successfully launched 146 satellite missions to date for a low per launch cost. A recent test of a helicopter retrieval of the 1st stage indicates that reusability is possible using this in-flight capture approach, therefore potentially saving costs. The kick stage in the image is replaced by the Photon rocket for interplanetary flight.
Figure 3b. High-energy Photon rocket and Venus entry probe.
Figure 3c. The small Venus probe is a 45-degree half-angle cone approximately 0.2m in diameter. Credit: NASA ARC.
Fast and Cheap
The cost of the mission to Venus is not publicized, but we know the cost of a launch of the Electron rocket to LEO is $7.5m [12]. Add the photon cruise stage, the entry probe, the science instruments, the operations and science teams. All in, a fraction of the Discovery mission costs, but with a faster payback and more focussed science. Rocket Lab has not launched an interplanetary mission before, so there is risk of failure. The company does have other interplanetary plans, including a Mars mission using two Photon cruise stage rockets for a Mars orbiter mission in 2024.
Is the Past the Future?
The small probe and dedicated instrument package, while contrasting with the big science missions of the national programs, harkens back to the early scientific exploration of space at the beginning of the space age. The smaller experimental rockets had limited launch capacity and the scientific payloads had to be small. Some examples include the Pioneer 4 lunar probe [11] and the Explorer series [10].
These relatively simple early experiments resulted in some very important discoveries. The lunar flyby Pioneer 4, launched in 1958, massed just 6.67 kg, with a diameter of just 0.23 m, a size comparable to the VLF’s first mission [11]. These early missions could be launched with some frequency, each probe or satellite containing specific instruments for the scientific goal. Today with miniaturization, instruments can be made smaller and controlled with computers, allowing more sophisticated measurements and onboard data analysis. Miniaturization continues, especially in electronics.
Breakthrough StarShot’s interstellar concept aims at have a 1 gm sail with onboard computer, sensors, and communications, increasing capabilities, reducing costs, and multiplying the numbers of such probes. With private funding now equaling that of the early space age experiments, and the lower costs of access to space, there has been a flowering of the technology and range of such private space experiments. The VLF mission is an exemplar of the possibilities of dedicated scientific interplanetary missions bypassing the need to be part of “big science” missions.
Just possibly, this VLF series of missions will return results from Venus’ atmosphere that show the first evidence of extraterrestrial life in our system. Such a success would be a scoop with significant ramifications.
References
1. Seager S, et al “Venus Life Finder Study” (2021) Web accessed 02/18/2022
https://venuscloudlife.com/venus-life-finder-mission-study/
2. Clarke A The Exploration of Space (1951), Temple Press Ltd
3. Ley, W, Von Braun W, Bonestell C The Exploration of Mars (1956), Sidgwick & Jackson
4. RocketLab “Electron Rocket: web accessed 02/18/2022 https://www.rocketlabusa.com/launch/electron/
5. Wikipedia “List of missions to Venus” en.wikipedia.org/wiki/List_of_missions_to_Venus
6. Wikipedia “DAVINCI” en.wikipedia.org/wiki/List_of_missions_to_Venus
7. Wikipedia “VERITAS” en.wikipedia.org/wiki/VERITAS_(spacecraft)
8. Wikipedia “EnVision” en.wikipedia.org/wiki/EnVision
9. Wikipedia “Venera-D” en.wikipedia.org/wiki/Venera-D
10. LePage, A, “Vintage Micro: The Second-Generation Explorer Satellites” (2015) www.drewexmachina.com/2015/09/03/vintage-micro-the-second-generation-explorer-satellites/
11. LePage, A, “Vintage Micro: The Pioneer 4 Lunar Probe” (2014)
www.drewexmachina.com/2014/08/02/vintage-micro-the-pioneer-4-lunar-probe/
12. Wikipedia “Rocket Lab Electron”, en.wikipedia.org/wiki/Rocket_Lab_Electron
https://www.youtube.com/watch?v=IlKwh1O9oVg&t=25s
Dmitry,
2 thoughts:
1. Have you contacted JP Aerospace to see whether they can help you with the project testing in the Earth’s atmosphere. Your femtosats are analogous to their pongsat program and they might well be an affordable way to test your probe deployment in a high stratosphere release.
2. I don’t know anything about the science of your Indicator Mission, but have you thought of contacting Sara Seager’s VLF team at MIT about a possible collaboration for the first balloon mission? If nothing else, you might get good feedback on your your experiment.
The sun is the hottest body in the Solar System.
Also, will exoplanet study reveal life that has not reached photosynthesis yet?
Technically, yes. See my CD article Detecting Early Life on Exoplanets that examines the spectrographic biosignature of Archaean methanogens on exoplanets.
I also recommend looking at Sara Seager’s paper on a proposed list of possible biosignature molecules in Toward a List of Molecules as Potential Biosignature Gases for the Search for Life on Exoplanets and Applications to Terrestrial Biochemistry.
Why the tremendous aversion to microscopes? They can be made light, and we now have capable AI to do in situ analysis of images.
Microscopes can certainly be made to be small, although the commercial consumer ones have insufficient magnification to see bacteria. In fact, most student lab microscopes can barely do this with 1000x oil immersion lenses. I have an Olympus CX22 microscope at home that was very similar to the student microscopes used in our undergraduate lab classes. Very nice kit but not suitable for anything much smaller than blood cells and yeast, both of which are much larger than bacteria.
So we would need a lightweight microscope similar in design to consumer small, portable, electronic microscopes with a magnifying power of 1000x plus. OTOH, if the cells are the size of eukaryotes, then one with 100-400x magnification would be sufficient.
The other possibility is to try to grow the sample on a medium as they did on Viking, and use a microscope as one instrument to look at the medium for colonies. Unfortunately, most terrestrial microbes cannot be cultivated this way, so this is a risky approach.
What about this?
https://www.techbriefs.com/component/content/article/tb/supplements/ptb/briefs/30030
There have been a number of such small SEM instruments whose price and size might just be suitable for the big-science Discovery/Flagship missions.
I’d like to know what the limitations are as a small SEM might be just the ticket to directly observing the presence of bacteria and other microbes, even viruses in samples. For bodies in space, like comets and asteroids, the instrument doesn’t even need a vacuum chanber.
Most of the out-of-this-world scientists’ acquaintance with microbiology labs is limited to getting their “tickets punched” for the mandatory requirements towards their academic degrees. And that, if there is such a reqirement for that degree.
With their acquaintance with microscopes thus limited, one should not expect microscopes to figure prominently in their thinkng.
That would be amazingly cool if they found Venusian life in the upper atmosphere. If nothing else, it would also spur some serious Venusian ground probes to study the geology and atmosphere, to see when it turned hostile.
It would also seriously burnish the credentials and standing of Seager and others of the VLF team, and certainly, put her in the history books.
As for the serious study of geology and atmosphere, that is supposedly what the DAVINCI+, VERITAS, Envision, and Venera-D probes are supposed to do at the end of this decade and the beginning of the next.
Rovers like those on Mars would be a serious engineering challenge but might have spinoff applications. When I was young, I recall a [semi-serious?] proposal to power rovers on Venus using wind turbines to drive the wheels or tracks. Demo scale models were run over a simulated rugged terrain in a tv studio, with fans providing the simulated winds. [I think it was an episode of the BBC’s “Tomorrow’s World”. My memory is of it is in B&W, suggesting it was pre-1970s.
Audacious yet intriguing! The thrill of discovery and the resultant fame and a Nobel prize or two are the drivers. My favorite science explainer had a less enthusiastic view of the claims of PH3 existing in the venereal atmosphere. I hope subsequent data showed her to be wrong.
https://www.youtube.com/watch?v=-xMRoICR9SE
A balloon-borne probe seems like an ideal way of atmospheric exploration but would be far more challenging from a cost and technology perspective. The Russians did it so it could certainly be done again but with a more capable science package.
The controversial PH3 signal might well prove as ephemeral as the claim for arsenic-based life, or the “fossil microbes” in the Martian meteorite.
However, there are other interesting anomalies that could be interpreted as indicators of life, and it should be noted that the first VLF mission is not looking for PH3, but rather different properties to look for life signs.
False claims constantly appear in science, some sensational. But the scientific method is self-correcting. Given the approximately 30% of false claims in psychology and medical papers, there should be some better way to exclude false claims, mostly due to small samples, contamination, p-hacking, and data mining. Some of those techniques can be countered, such as medical journals requiring the purpose of the experiment to be available before the experiment is attempted to prevent data mining for significant effects, as well as better use of statistical techniques.
“Is the life elsewhere in the universe” is one of those big questions that will attract lots of attention, and an unambiguous positive result will be very significant.
There are some papers against the biologic origine of phosphine in Venus:
https://www.pnas.org/doi/full/10.1073/pnas.2121702119
https://ui.adsabs.harvard.edu/#abs/2021NatAs…5..631V/abstract
I am glad you raised this issue, as it allows me to make some points:
1. Science works via repeatable experiments, not speculation. There may be good reasons to be skeptical of life in Venus, but that is why the only good approach is to do the experiments. That will eventually clarify the case whichever way the truth lands. No amount of Aristotelian “speculating on the number of teeth a horse has” beats actually doing the count.
2. Take special note of the timing as well as the low cost. This touches up a theme of the last post – the “Wait Equation”. This mission is based on the idea that going ahead to look for lfe now is better than waiting for the slow, deliberative approach of the national space agencies as exemplified by the search for life on Mars since Viking. I hoped that was clear in the essay.
Lastly:
3. This is a private venture. It will not reduce public funding for other science. Millner has every right to spend his money any way he likes. Doing science rather than building another superyacht seems like a good tradeoff to me (but I am biased)
[I have a short comments discussion with the inestimable Dwayne Day on The Space Review commenting on an article on CubeSats by Jeff Foust. He is countering my argument about the value of CubeSat type missions for interplanetary science. He makes good arguments, although I believe he will be proven wrong as small probe missions gain technological maturity.]
With no ill will towards any Venutians, I would prefer to find a mature prebiotic environment. Somehow geochemistry transforms into biology. We would learn more about abiogenesis from an ecosystem at or near the transition. With that crucial information we could better predict where life is possible.
Thank you Alex Toley. I am a sucker for numbered lists.
Where are you hoping to find such an environment, and how could we recognize such an environment? Europa, Titan? What features would be needed to be reached between the available organic molecule precursors and life? Is it gradual or does life make a phase change that rapidly changes from pre-biotic to life? IDK.
OTOH, recognizing life might be a lot easier, and in turn, provide such pre-biotic clues if the biology is very different.
In either case, if one is interested in biology and life in the universe, missions dedicated to uncovering these questions are more interesting than other science goals, unless teh overlap of information is clear.
I am not suggesting this mission be cancelled, hard to complain about low cost missions that could deliver ground breaking discoveries, just hoping the mission delivers a negative result. Since biology must arise from geochemistry, missions studying geology and geochemistry do overlap with missions searching for biology.
On Earth, life has erased evidence of the transitional ecosystem and left us largely confused about the nature of this transitional ecosystem. That is likely to be repeated wherever life emerges. A unique biology may offer some clues or leave us as confused. All of our theories for abiogenesis predict stable, transitional ecosystems and the only way we can confirm how that transition occurs is on a world where abiogenesis failed.
Any body where we can predict life will struggle to emerge is a candidate for a mission. Though, I don’t see how we could study a transitional ecosystem without electron microscopes, mass spectrometers, a whole lab I guess.
Geochemistry > RNA: https://www.science.org/content/article/did-volcanic-glasses-help-spark-early-life
There are quite a few acidophilic organisms. Most of them need a pH above 1 or 2 ( https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8751164/ ), which is likely to disqualify them here, but I’ve seen figures of pH 0.2 ( https://pubmed.ncbi.nlm.nih.gov/29414445/ ) or maybe even lower, though the details need close checking.
The first step on Venus needs to be some basic observation of the clouds (but some here may be able to fill in more here from what is known already!). Overall, Venus contains H2SO4, with a little bit of extra SO3 gas in the atmosphere (like “fuming” sulfuric acid), plus some water vapor that was never lost. However, when there are two different liquids involved, it starts to seem reasonable to think about rain falling on clouds! Does the drastic environment of Venus distill some of the water out of the H2SO4 and deposit it back unequally, so that there are some environments with a less acidic pH?
The many prior probes that analyzed the clouds have done the work you indicate, given the instruments available. AFAIK, there is no low-acid water droplet layer in or below the clouds. Overall, as you say, the Venusian clouds are very dry, with little scope for means to separate the H2SO4 from the little amount of water present.
If there is life derived from an earlier, more clement, surface ocean it is possible the internal pH of the cells might not be terribly acidic (admittedly that would be quite a proton pump!). How would this affect the autoflourescence required by the detector?
As you note, there is no requirement for the intracellular medium to be the same pH as the environment. IDK what the case is with terrestrial acidophiles. However, there are other ways of reducing pH, by neutralizing some of the acidity with bases. The VLF team speculates that this is the way any Venusian life does this, e.g. using ammonia-based molecules.
AFAICT from the prior experiments the team has done with autofluorescence, organic molecules can be detected in the whole range of H2SO4 concentration from 0-70% sulfuric acid.
Apparently terrestrial acidophiles actually do maintain an internal pH near neutral, with a huge pH gradient across their membranes.
Life in acid: pH homeostasis in acidophiles
Interesting paper showing the possible approaches to reducing free protons in the cytoplasm. Proton pumps and sequestering are the 2 main mechanisms.
I don’t know what the energetics of the reactions are, but I do wonder if the production of phosphine by hypothetical life in Venus is possibly a mechanism to remove protons.
I wonder if the fact that almost all terrestrial environments are near neutral doesn’t weight the evolutionary race in favor of a neutral intracellular environment? Because almost any organism that departed from that would be disadvantaged in virtually every environment.
Extremophiles live in environments that are, geologically, transitory. Their survival over time requires getting from one isolated extreme environment to the next, they *must* be able to at least survive neutral environments.
In the Venusian atmosphere, the extreme environment is there for good, and everywhere, so mutations in favor of an acidic internal environment would never be disadvantageous on that basis alone.
I doubt for reasons of chemistry that it would ever reach equilibrium with the atmosphere, (Terrestrial life hasn’t tracked ocean salinity, after all!) but if we find Venusian cloud life, I’d expect it at least to have evolved somewhat in that direction.
I have visions of Scott’s Alien with acid blood. ;)
The question is whether a more acidic cytoplasm has any possible selective advantages over better pH reduction mechanisms. My knowledge hits a wall in this regard. That acidophiles maintain their pH rather than adapt to the acidity seems like evidence that even rapidly evolving bacteria do not survive with lower internal pH. Why do they evolve mechanisms to keep their cytoplasm at a stable pH using a number of different mechanisms (all suggested for speculative life in the Venusian clouds) rather than adaptations to allow the internal pH to fall, even modestly? I do not think the argument that the terrestrial acidophiles must traverse non-acidic environments works. Many extremophiles are obligates to their conditions, unable to survive elsewhere, suggesting, to me, that they have found the better/best solution for survival. It may be that adapting existing mechanisms is more probable than trying to simultaneously adapt all proteins and metabolic activity to lower pH conditions. [It is through these multiple points of attack that new ideas for controlling pathogens are being developed.]
As evolution on Earth has maintained core metabolisms and proteins, as well as maintaining the reproduction mechanisms of DNA->RNA->proteins, I believe that any Venusian organisms would do the same as a wholesale internal adaptation to the acidic conditions would be so difficult as to be a vanishingly low probability compared to adapting the biology to maintain the conditions of the ancient Venus.
(Weasel words): “vanishingly low probability”, but not zero?
I would like to see a larger lander on Venus by NASA which includes a seismometer and seismograph to detect Venus quakes which would allow us to learn about the interior of Venus and more about it’s geology. Because of gravity, it is hard for me to imagine that life could evolve to stay aloft especially single celled life. I thought there might be micro fossils of aerobic micro organisms underground, or maybe the mountain tops, or “some of the ridges found on tesserae terrains, particularly in Ishtar Terra, form large mountain (or mons) belts.” Wikipedia. Once they became fossilized, the might be able to survive the heat. They could be chemically detected with a x ray spectrometer with an extension or mechanical arm might work.
Life was thought to exist on Mars, but animal life was ruled out on Venus in the 1950’s by scientists. Popular imagination and science fiction kept the life on Venus alive until the Mariner 2 Venus mission in 1962. “The kind of animal or vegetable life that we know on Earth probably could not exist on Venus. Observations with a spectroscope show carbon dioxide in the atmosphere, little or no free oxygen and almost no water.” Quote from National Geographic, January, 1953. Photograph’s taken with Mount Palomar’s telescope article. P. 125
Also In 1956, The US Naval Research Laboratory in Washington used a 50 foot dish to observe Venus which radiates radio waves between 3 to 10 centimeters which can only result with a surface temperature of over 300 degrees centigrade. Taylor, 2014.
Obviously, the mission is dedicated to finding life, not geology. The national missions coming at the end of the decade are looking into doing geology. The VLF probe will reach the ground but the data transmission stops below the cloud layer. The mission would be different if it was hoped for a probe to reach the ground, but that is outside of the scope of the mission, as none expects any life to be viable in the conditions on the surface.
As we have discussed in other posts, a body with a cool surface and a hot interior will have a zone that allows water to be in a liquid state, allowing subsurface life. This does not seem possible on Venus.
As I note in the article, prokaryotic life does exist in terrestrial clouds. A high surface-to-volume ratio allows such life to be kept aloft in air currents. There is a question if this life is independent of the surface or not.
With suitable evolved forms, even complex life could stay aloft. Envelopes of low-density gas could keep such creatures floating in the atmosphere, or dynamic soaring using thermal updrafts and wind shear can also be used. On Earth, baby spiders use threads of web material to catch winds to carry them aloft. The dense Venusian air might have allowed the evolution of the equivalent of buoyancy organs like fish swim bladders or behavioral approaches like secreting bubbles of gas.
The VLF team is aiming for the most likely life form that has been ubiquitous on Earth for billions of years, rather than the more recent complex life that emerged within the last billion years. To appropriate the SETI analogy, if all you can do is sample the ocean with a single drinking glass, don’t expect to find fish, but do look for microbes.
Alex Tolley:
Would you expect life that arose independently on Venus to use DNA/RNA for information storage with our identical genetic code, or, would you expect such life to be based on a completely different information storage organic polymer and a different set of amino acids for structural and catalytic purposes?
If subject to different environmental stresses early in abiogenesis, nucleic acid analogues may win in the fitness contest. This could also happen by the luck of the draw.
The fundamental questions are:
1. Is there life on Venus (indeed extraterrestrial life)
2. How comparable is it to terrestrial life. Due to the closeness of our 2 worlds, the underlying question is if Venusian life exists, and whether we share a common abiogenesis or not.
So there are possibly many shades of similarities and differences.
Is the old terrestrial mechanism of DNA->RNA->proteins the same, or not.
If DNA is used, is it the same as ours, or uses different nucleic acid bases? Does it use D-sugars to create its chirality? Are the proteins composed of the same 20 amino acids? Are the proteins of the same L-chirality? If it is the same, is the genetic code (3-base codon sequence to an amino acid) the same?
Are the core energy metabolisms the same?
How will we tease apart the similarities and differences to answer the question about sources of abiogenesis?
It would be easy to answer that question if the biology was so different that there was almost no similarity between terrestrial and Venusian life.
However, there was (is) quite possibly a transfer of microbial life from one world to the other. When they may have been similar, a lifeform could have survived in both environments. This is no longer true for terrestrial life that would be destroyed in the acid clouds of Venus. So far we have not had any evidence of life adapted to Venus living on Earth. [But as with SETI, we have hardly sampled the microbial life, and if it was very different, we wouldn’t detect it by DNA methods.]
The VLF team has wisely avoided the issue with this first probe by looking for:
1. Cloud droplets that are not forced by physics to be spherical and detected by the nephelometer. Rod-shaped droplets like bacillus or a prolate spheroid like coccobacillus.
would be examples. This non-spherical shape has been reported for some fraction of the droplets with prior probes.
2. Organic molecules in the droplets detected by autofluorescence. [Terrestrial organic molecules would be destroyed, so there would be no false positives.] This is not definitive for life as organic molecule residues do appear in chemical processes using very concentrated H2SO4, but it is suggestive.
My sense is if both of these are found, then this puts urgency to do the next mission using a balloon and with more instruments. OTOH, if neither are found, the likelihood of life in the clouds is diminished.
If life is found that last mission to return a sample to Earth is important. It will contain a treasure trove of unique biology. However, it would have to be analyzed and cultured in a biohazard facility until it could be confirmed that the microbes are safe to be run in labs with standard biohazard waste protocols. The explosion of journal papers on Venusian biology would be obvious, with no doubt specialty journals appearing rapidly. The biology would require lifetimes of study.
@Alex Tolley:
If other life we might find someday in the solar system is found to have an identical biochemistry to life on Earth using the familiar DNA–>RNA–> Protein template (even down to identical chirality etc.), then how can we be sure that this other life did not actually arise from a separate genesis? In other words, is there any way to even roughly quantify the likelihood that life from a second genesis would use our exact same template as opposed to one based on another family of organic compounds (e.g. polyaromatic sulfonyl halides)? How would you answer the person who maintains that, say, the microbes found on Enceladus even though they have biochemistry identical to Earth-based life are actually from an independent genesis which is reflective of some sort of built in tendency for the “terrestrial” DNA, RNA, protein system to arise after all on a variety of different planetary bodies?
Some have mentioned on here that life from an independent genesis would follow terrestrial biochemistry almost exactly or at least close enough to be indistinguishable from terrestrial biochemistry. Personally, I find this rather presumptuous and unlikely but I was wondering, Alex, what do you think the likelihood is that life would use a different set of organic molecules compared to those used by Earth-based life? A set of organic compounds and metabolic processes that would clearly allow us to say unequivocally that this life arose from an independent abiogenesis?
It’s an interesting question. The reality is that we don’t know much about this issue.
I would say that since we know that there can be small differences in the genetic code in bacteria, that in the lab we have artificially changed the genetic code to add new amino acids, and even altered the tRNA to work with a 4-base codon, and of course, there are many different metabolisms using a common core, that it seems unlikely that any de novo abiogenesis would end up with a biology pretty much identical to terrestrial biology. I would certainly jump to the side of those who argue for a common source for the biogenesis, whether from Earth, the other world, or a 3rd world elsewhere. But that is just my bias based on the idea that the genetic code is a “frozen accident” and could have other equally good alternatives.
For our terrestrial tree of life, we use gene DNA sequences to relate one species to another. If we found life on another world with the identical biology, but with no commonality of gene or amino acid sequences, then this would be a strong argument that this life separated from Earth life at a very early stage, possibly even before the putative last universal common ancestor (LUCA). But we would still have the issue of a common abiogenesis. I would still say a common biogenesis, but I would keep an open mind based on future discoveries.
Bottom line is that I think that probability argues against separate abiogeneis events converging on an identical biology, but it is possible that the viable design space is so narrow that the assumed freedom to use different biology is false and that evolution strongly converges to an identical biology to ours.
But if anyone wants to argue for the other case, I’m game.
This is a great mission to our close cousin and much easier then Mars missions, one reason the Russians where so prevalent in studying Venus.
The possibility that Venus was destroyed as recently as 800 millions years ago by a giant impactor is also a good reason to look for life that may have survived in the atmosphere. As we have found on earth that there is a deep biosphere in the depths of our crust could life survive in Venuses deep crust? Would there be some surface or atmospheric indicators from such biology and could areas in the deep lithosphere be cooler then the surface?
As I say in reply to Geoffrey:
Well, here is some interesting news that would put life on early Venus.
JUNE 3, 2022
Scientists announce a breakthrough in determining life’s origin on Earth—and maybe Mars.
“Scientists at the Foundation for Applied Molecular Evolution announced today that ribonucleic acid (RNA), an analog of DNA that was likely the first genetic material for life, spontaneously forms on basalt lava glass. Such glass was abundant on Earth 4.35 billion years ago.”
https://phys.org/news/2022-06-scientists-breakthrough-life-earthand-mars.html
I look forward to more research data on this finding. If long, linear RNAs do form this way, it is a strong boost for the RNA-World theory.
The next issue is where these basaltic glasses are found. They are formed by hydro-volcanic processes and impacts. So they should be common in many terrestrial locations. They are also found [by the Curiosity rover] in the Martian regolith which would favor the idea of Mars being a possible abiogenesis location during its early history. I would guess the same would apply to Venus.
@Alex Tolley:
I was very excited upon hearing about this work suggesting that the geological production of RNA strands of a length sufficient for chemical evolution may occur readily on terrestrial planets with the right geology.
The Event Horizon channel on YouTube has a good video covering this recent work on the potential geological production of RNA. This exciting new idea could presumably be tested by going to locations on Earth where the geology is favorable to the production of RNA strands and actually seeing how much, if any, RNA is actually being made by the processes described at present. Perhaps we could also test the hypothesis by checking for geological production of RNA strands on the Red Planet.
Clearly, this new work on the geological production of RNA strands represents a breakthrough in the study of abiogenesis. Let’s assume that the RNA did form this manner in large quantities during the Hadean period. The question then becomes how did it couple with metabolic processes like the Citric Acid Cycle inside a protocell. For example, how did RNA and metabolism become part of a protocell which then produced more protocells, and so on? And, among these various steps in abiogenesis, how can we begin to quantify the likelihood that these would occur in any given period of time? In other words, it could be that RNA strands of a size sufficient for chemical evolution occur readily in the geological context described in the paper, but how readily do these RNA strands enter into micelles and how do these micelles come to acquire the metabolic framework.
Another question: if RNA strands of a sufficient length for chemical evolution occur readily, how much does this new information allow us to update (I am thinking Bayesian stats here) the probability of abiogenesis?
There are several possibilities on how this sequence might occur:
1. RNA, protocell, metabolism
2. Protocell, RNA, metabolism
3. Metabolism, protocell, RNA
4. Metabolism, RNA, protocell
5. Protocell, metabolism, RNA
6. RNA, metabolism, protocell
Then, of course, DNA and the genetic code become part of the equation as well.
If this pans out, then it certainly lends support for the RNA-World model. Remember that single-stranded RNA. unlike double-stranded DNA, can have useful tertiary structures and act like proteins. They still play a role in this regard in some processes, most notable in translation with tRNA. Would RNA need a cell? I don’t believe so. Similarly with metabolism, although metabolism does ideally need some way to constrain substrates and metabolites. There have been a number of ideas on how to determine what the last pre-biotic stages might look like, or the first basic cell.
If the RNA-World model is correct, then this easy production of longish [linear] chains of RNA might allow the exploration of RNA space, producing chains that autocatalyze more of themselves and start off the selection process and RNA evolution.
But note the work on deep-sea vents in basic rocks that favor protein formation. Proteins do not self-catalyze, AFAIK, so at some point, RNA would need to direct the formation of functional proteins that would include the catalysis of metabolic pathways. Would the genetic code start here, or would RNA molecules produce proteins in a different way than their transcription (mRNA) and translation (tRNA) functions today?
One useful result of this work is that since glass-basalts are so common, and RNA chains readily form, we should be able to detect their presence on worlds in a prebiotic state. If Europa or Enceladus is still prebiotic, shouldn’t we be able to detect RNA chains that have not been degraded by UV or heat? Would not the plumes have these chains? I don’t recall any analyses even hinting at this, so either this formation is not occurring on Europa, or life is present and these chains, if they occur, are consumed. [I am sure there are other possibilities]. If we look for these rocks in the Martian subsurface, is there any chance that fragments of these chains have “fossilized” and can be detected by laboratory analysis? [It doesn’t even matter if the chains are linear or branched.]
Does anyone else have ideas on the detection of these RNA chains? [Mass spec, and RNA chips would be 2 possible detection methods.] And if they can be detected, what would be the implications for the state of the world they are found on?
Perhaps a surface sample, we drop a tank of compressed gas or water to make steam and make a rocket out of it which uses the thermal heat of venus to propel it back up.
Hi Alex & Paul
There’s a recent paper in PNAS suggesting that ammonia might play a role in Venus’s clouds, to make them more hospitable:
Production of ammonia makes Venusian clouds habitable and explains observed cloud-level chemical anomalies
Confirming the presence of ammonia should also be a science goal, if the modeling by Bains et al is correct.
Wow! If this holds up, this is like finding a whole new planet next door – one with clouds of sulfurous acid, not sulfuric, occurring as the salt, not the free acid, and with a pH of 1, not -11! Powered by … biological nitrogen fixation? That produces oxygen? This is some heady stuff.
The paper doesn’t really talk much about the oxygen, except to acknowledge that it has to be produced in order to wring out scarce hydrogen to make ammonia. I see a figure that the O2/CO2 ratio is 3e-7 or less ( https://ntrs.nasa.gov/search.jsp?R=19830062870 ), so it has to be consumed somehow, but with what? Or… is it sequestered??? Remember, O2 is a lift gas on Venus!
I had assumed ammonia had a snowball’s chance on Venus, but if this detail is right and the rest is wrong, it could end up leading to the most amazing notions.
Thanks for highlighting the reference. The VLF document includes a very short mention of ammonia as a means to increase pH and the link is actually the 3rd citation in the documents reference section.
Given all the comments are about the science, not the means of getting to Venus with a low mass probe and inexpensive small launcher, do we need a new article on the scientific arguments for and against life on Venus, and the proposed instruments and experiments to determine if life exists on Venus?
An article on the proposed instrumentation would certainly be to the point. Good idea.
I was initially disappointed to see a news article yesterday ( https://www.nature.com/articles/s41467-022-30804-8 ) based on a paper asserting that “proposed energy-metabolisms cannot explain the atmospheric chemistry of Venus”. However, the paper ( https://www.nature.com/articles/s41467-022-30804-8 ) only evaluates biochemistry depending on the presence of H2S or CO, both of which they say are not present at anywhere near the level needed. I’m not sure why they picked those, since both can act as Lewis bases, unlike ammonium ions. Also, some uses of “it’s” give the impression Nature Communications is not heavily edited, shall we say. For now I don’t think I’ll reduce the odds of life on Venus in my mind … fortunately, as there was not very much room to do so to begin with.
Apologies if it’s already been linked, but here’s a good site for info on early space missions, including Venus probes:
https://www.drewexmachina.com/blog/
Drew does a wonderful job, and has on occasional written articles for Centauri Dreams. I recommend his blog to anyone interested in exoplanet research.
Figure 3C shows what must the reentry vehicle. But would it be helpful to deploy a drag chute or the like to slow the decent through the atmosphere to increase the time for measurements?
The first probe is the simplest, least complex, approach to capturing the data desired. The entry probe falls through the dense atmosphere and only needs to survive up to 300 seconds of data acquisition and transmission time as it enters and exits the cloud layer.
The next proposed mission (Habitability) is more extensive, with balloons and samplers. Figure 4-7 in the referenced VLF report shows the use of a number of parachutes to aid the deployment of the various components. This mission is more complex, with more instruments and mass, and starts to depart from the simplicity of the first mission.
Thank you! Your expertise and enthusiasm for sharing knowledge is greatly appreciated!
Quoting from the main article:
“In addition, Russia has the Venera-D mission planned for a 2029 launch that has a lander. One of its goals is to analyze the chemical composition of the cloud aerosols. [8]”
Here is the most recent information on Venera D, which looks different from previous depictions of the probe:
http://www.russianspaceweb.com/venera-d-2021.html
To quote from the above linked page:
“Perhaps, the 2029 launch date reflected the expected funding and technical challenges before the Venera-D project.”
If Venera D does ever get built and launched, the Russians will be going it alone:
http://www.parabolicarc.com/2022/02/26/roscosmos-ends-u-s-participation-in-venera-d-mission-to-venus/
https://twitter.com/katlinegrey/status/1497478759464812544
Will they want to relive their glory days of exploring the second world from Sol? Back in the day at least one of their scientists publicly exclaimed they were tired of going to Venus. However, I can see multiple current political reasons why they might want to revise their space efforts for that planet.
Whether Venera D actually gets built, then makes it first into space and then to Venus will decide if our nearest planetary neighbor becomes part of their expansion plans.
I am also skeptical of the ability of Russia to carry out science space missions. It seems that they are ever more prolific in proposing space technology, lavished with CGI, but failing to actually progress the technology. The recent failures of their mature launchers and spacecraft add to the perception that their capabilities are not good. I recall that after the breakup of the USSR, Russia did not have the capability of producing the guidance hardware for their Progress craft, resulting in a collision with Salyut attempting a manual docking. The recent revelations that Russian military hardware is using scavenged microchips and that their fighter planes were using commercial GPS units taped to the “dashboard” suggest, to me, that Russia’s technological capabilities may have peaked and be on the decline.
While Russia acts as a Great Power, with a permanent position on the UN Security Council, its economy is about 40% of Germany’s on a nominal basis, and about 90% of Germany’s on a purchasing power parity basis.
The last time Russia sent a probe to Venus was with their Vega-2, in 1985, before the breakup of the USSR. It is questionable if they have the economic and technological capacity to even repeat these efforts, let alone match the more recent missions under development by NASA and ESA, and even the increasingly capable ISRO.