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The Great Venusian Bug Hunt

Our recent focus on life detection on nearby worlds concludes with a follow-up to Alex Tolley’s June essay on Venus Life Finder. What would the sequence of missions look like that resulted in an unambiguous detection of life in the clouds of Venus? To answer that question, Alex takes the missions in reverse order, starting with a final, successful detection, and working back to show what the precursor mission to each step would have needed to accomplish to justify continuing the effort. If the privately funded VLF succeeds, it will be in the unusual position of making an astrobiological breakthrough before the large space organizations could achieve it, but there are a lot of steps along the way that we have to get right.

by Alex Tolley

In my previous essay, Venus Life Finder: Scooping Big Science, I introduced the near-term, privately financed plan to send a series of dedicated life-finding probes to Venus’ clouds. The first was a tiny atmosphere entry vehicle with a dedicated instrument, the Autofluorescing Nephelometer (AFN). The follow-up probes would culminate in a sample return to Earth, all this before the big NASA and ESA probes had even reached Venus at the end of this decade to investigate planetary conditions.

When the discussion turns to missions on or around planets or moons that may be home to life, the focus is on whether these probes could be loaded with life-finding instruments to front-load life detection science. The VLF missions are perhaps the first, to make detecting life the primary science goal since the Viking Mars missions in the mid-1970s, with the possible exception of ESA’s Beagle 2 (Beagle 2 lander’s objectives included landing site geology, mineralogy, geochemistry, atmosphere, meteorology, climate; and search for biosignatures [8]).

The approach I am going to use here is to start with what an Earth laboratory might do to investigate samples with suspected novel life. I will then reverse the thinking for each mission stage until the decision to launch a Venusian atmosphere entry AFN becomes the obvious, logical choice.

So let us start with the what science and technology would likely employ on Earth, assuming that we have samples from the VLF missions previously undertaken that indicate that the conditions for life are not prohibitive, and earlier analyses that suggest that the collected particles are not just inanimate but appear to be, or contain life. As we do not know if this life is truly from a de novo abiogenesis or common to terrestrial life and thus perhaps from Earth, there are a number of basic tests that would be employed to determine if the VLF samples contain life.

The key analyses would include:

1) Are there complex organic molecules with structural regularities rather than randomness? For example, terrestrial cell membranes are composed of lipid chains with a certain length of the carbon chain (phospho- and glycolipids peak at 16- and 18-length chains). Are there high abundances of certain molecules that might form the basis of an information storage molecule, e.g. the 4 bases used in DNA – adenine, thymine, guanine, cytosine, or an abundance subset of the many possible amino acids?

2) Are the cell-like particles compartmentalized? Are there cell membranes? Do the cells contain other compartments that manage key biological functions [5]?

3) Do the molecules show homochirality, as we see on Earth? If not, and the molecules are racemic as we see with amino acids in meteorites, then this indicates a non-biological formation. Terrestrial proteins are based on levorotatory amino acids (L-amino acids), whilst sugars are dextrorotatory (D-sugars).

4) Do the samples generate or consume gases that are associated with life? This can be deceptive as we learned with the ambiguous Viking experiment to detect gas emissions from cultured Martian regolith. Lab experiments can resolve such issues.

5) Do the samples have different Isotope ratios than the planetary material? On Earth, biology tends to alter the ratios of carbon and oxygen isotopes that are used as proxies in analyses of samples for paleo life. For example, photosynthesis reduces the C13/C12 ratio and therefore can be used to infer whether carbon compounds are biogenic.

Note that the goals do not initially include using optical microscopes, or DNA sequencers. Terrestrial life is increasingly surveyed analyzing samples for DNA sequences. DNA reading instruments will only work if the same nucleobases are used by Venusian life. If they are, then there is the issue of whether they come from a common origin to terrestrial life. For bacteria-sized particles, electron microscopes are more appropriate.

The types of instruments used include mass spectrometers, liquid and gas chromatographs, optical spectrometers of various wavelengths, nanotomographs (nano-sized CT scans), atomic force microscopes, etc. These instruments tend to be rather large and heavy, although specially designed ones are being flown on the big missions, such as the Mars Perseverance rover. Table 1 below details these biosignature analyses to be done on the returned samples.

Table 1 (click to enlarge). Laboratory biosignature analyses for the returned samples, the instruments, and the specific outputs.

For the goal of detecting biosignature gases and their changes, table 2 shows the prior information collected from probes and telescopes that might indicate extant life on Venus.

Table 2 (click to enlarge). Prior data of potential biosignature gases in the Venusian atmosphere.

Given that these are the types of experiments on samples returned to Earth, how do we collect those samples for return? Unlike Mars, life on Venus is expected to be in the clouds, in a temperate habitable zone (HZ) layer. The problem is not dissimilar to collecting samples in the deep ocean. A container must be exposed to the environment and then closed and sealed. Apart from pressure, the ocean is a benign environment.

Imagine the difficulties of collecting a sample near the bottom of a deep, highly acidic lake. How would that be done given that it is not possible to take a boat out and lower an acidic resistant sample bottle? The VLF team has not decided how best to do this, but the sampling is designed to take place from a balloon floating in the atmosphere for the sample return mission.

Possible sampling methods include:

  • Use of aerogels
  • Filters
  • Electrostatic sticky tape
  • Funnels, jars, and bottles
  • Fog Harp droplet collector
  • Gas sampling bags

In order to preserve the sample from contamination and to ensure planetary protection from the returned samples, containment must be carefully designed to cover contingencies that might expose the sample to Earth’s biosphere.

Note that this Venus Return mission is no longer a small project. The total payload to reach LEO, that includes the transit vehicle, balloon and instrument gondola, plus Venus ascent vehicle, and transit vehicle to Earth, is 38,000 kg, far more massive than the Mars Perseverance Mission, double the launch capability of the Atlas V and Ariane V launchers, and requiring the Falcon Heavy. The number of components indicates a very complex and difficult mission, probably requiring the capabilities of a national space organization. This is definitely no longer a small, privately funded, mission.

But let’s backtrack again. The samples were deemed worth the cost of returning to Earth because prior missions have supported the case that life may be present in the atmosphere. What experiments would best be done to make that assessment, given a prior mission that indicated this ambitious, complex, and expensive effort was worth attempting?

The science goals for this intermediate Habitability Mission are:

1) Measure the physical conditions in the cloud layer to ensure they are not outside of a possible extremophile range. The most important metric is perhaps temperature, as no terrestrial thermophile can survive above 122 °C, nor metabolize in solids. A lower bound might be that water freezes at 0 °C, although salt water will lower that freezing point, so halophiles could live in salty water at below 0 °C. Is there water vapor in the clouds that indicates that the particles are not pure sulfuric acid? Allied with that, are the particles less acidic than pure H2SO4? Are there non-volatile elements, such as phosphorus and metals, that are used by terrestrial biology to harvest and transfer energy for metabolism?

2) Can the organic materials previously detected be identified to indicate biologic rather than abiologic chemistry? Are there any hints at compound regularity that will inform the sample return mission? Can we detect gas changes that indicate metabolism is happening, and are the gases in disequilibrium? Of particular interest may be the detection of phosphine (PH3) emissions, an unambiguous terrestrial biosignature, detected in the Venusian clouds by terrestrial ground-based telescopes in 2020.

3) Are the non-spherical particles detected in a prior mission solid or liquid, and are they homogeneous in composition (non-biologic) or not (possible life).

To be able to do these experiments, the mission will use balloons that can float in the Venusian clouds. They may need to be able to adjust their altitude to find the best layers (but this adds complexity, risk, and cost) and travel spatially, especially if there is a desire to sample the patchy cloud layers that are strongly UV absorbing and have been likened to algal blooms on Earth.

A balloon mission is quite complex and carries a number of instruments, so that cost and complexity is now substantial. A simpler, low-cost, prior mission is needed that will capture key data. What is the simplest, lowest mass mission possible that will inform the team that this balloon mission should definitely go ahead if the results are positive? What science goals and instrument[s] could best provide the data to inform this decision?

This earlier mission is designed around two sources of information that it can leverage. First, there are the many Venus entry probe missions from the early 1960s to the mid 1980s. The most intriguing information includes the observation that there were particles in the clouds that were not spherical as would be expected by physics, and this non-spherical nature might indicate cellular life, such as bacilli (rod-shaped bacteria).

Shape however, is insufficient, as life must be able to interact with the environment to feed, grow, and reproduce. On Earth, these functions require a range of organic molecules – proteins, DNA, RNA, lipids and sugars. This implies that organic compounds must be present in these non-spherical particles; otherwise the shape may be due to physical processes, including agglomeration and/or merging of spherical particles.

The VLF team is also testing some of the assumptions and technology in the lab, confirming for example that autofluorescing of carbon materials works in concentrated sulfuric acid. Their lab experiments show that linear carbon molecules like formaldehyde and methanol in concentrated H2SO4 result in both UV absorption and fluorescence over time, implying that the structures are altered, as is found in industrial processes. From the report:

If there is organic carbon in the Venus atmosphere, it will react with concentrated sulfuric acid in the cloud droplets, resulting in colored, strongly UV absorbing, and fluorescent products that can be detected (…). We have exposed several samples containing various organic molecules (e.g., formaldehyde) to 120 °C, 90% sulfuric acid for different lengths of time. As a result of the exposure to concentrated sulfuric acid all of the tested organic compounds produced visible coloration, increased absorbance (mainly in the UV range of the spectrum), and resulted in fluorescence (…)

It should also be noted that Misra has shown that remote autofluorescing can detect carbon compounds and distinguish between organic material (leaves, microbes on rocks, and fossils) and fluorescing minerals [6,7].

Table 3 (click to enlarge). The science goals for the balloon mission, showing that the AFN is the best single instrument to both detect and confirm the non-spherical particles found in the prior Venus probes, and the presence of organic compounds in the particles. It can also determine whether the particles are liquid or solid, and estimate the pH of the particles.

Of the possible choices of instruments, the Autofluorescing Nephelometer (AFN) best meets the requirements of being able to measure both particle shape and the presence of organic compounds. This can be seen in table 3 above for the science goals of the balloon mission. The instrument is described in the prior post and in more detail in the VLF Report [1]. Ideally, both conditions should be met with positive results, although even both together are suggestive but not unambiguous.

Organic compounds can form in concentrated H2SO4, and cocci are essentially spherical bacteria. Nevertheless, a positive result for one or both justifies the funding of the follow up mission. Conversely, a negative result for both, especially the absence of detectable organic compounds would put a nail in the coffin of the idea that there is life in the Venusian clouds (a classic falsification experiment) – at least for that 4-5 minute data acquisition mission as the probe falls through the HZ layers of clouds where these non-spherical particles have previously been detected.

It could certainly be argued that life is patchy, and just like failing to catch a fish does not mean there are no fish to be caught, it is possible that the probe fell though a [near] lifeless patch and that other attempts should be made, for example the balloon mission that will take measurements over a wider range of space and time.

The first VLF probe mission begs the question of why we should even consider Venus as an abode for life. The prior missions have shown that the surface is a very hot, dry, and acidic environment which is inimical to life as we know it. The only suggestions for the presence of life are the aforementioned patchy UV absorbing regions implying organic compounds in the clouds, and the presence of the biosignature gas PH3.

For life to be on Venus, either the conditions must once have been clement to allow abiogenesis, or life must have been seeded by panspermia to allow it ultimately to evolve to survive in the cloud refugia when the oceans were lost during the runaway greenhouse era. Is there any evidence that Venus was once our sister world with conditions like Earth, but warmer, before the runaway greenhouse conditions transformed the planet?

The scholarly literature is divided, from the optimistic view of Grinspoon [2] and others that Venus had an early ocean that lasted for long enough (e.g. 1 Gy), to support life [3], to the pessimistic view of Turbet [4] that modeling suggests Venus never had an ocean (and that Earth was only able to condense one during the faint young sun period.

It is to try to answer these questions that the science goals of NASA’s and ESA’s DAVINCI+, VERITAS, and EnVision probes are designed to meet.

The VLF team, however, have supported their plan with the optimistic view that early Venus was clement and that life could have taken hold, and therefore a series of dedicated, life-finding missions will best answer the question of whether there is life on Venus, rather than establishing that a paleo climate on Venus was indeed present and lasted long enough to allow life to emerge, or long enough for it to have been transferred from Earth by the time we are sure life on Earth was present.

If the first VLF mission returns positive results, then it seems likely that the following missions, however designed and by whom executed, will push forward the science goals toward more life detection. Negative results could well derail subsequent life detection goals. The time frame will overlap with the Mars sample return mission that will collect the Perseverance rover samples for analyses back on Earth. It may well also overlap with the early results of biosignature detection on exoplanets. Whatever the outcome, the end of this decade will be an exciting time and will pose fundamental questions about our place in the galaxy.


1. Seager S, et al Venus Life Finder Study (2021) Web accessed 02/18/2022 https://venuscloudlife.com/venus-life-finder-mission-study/

2. Grinspoon, David & Bullock, Mark. (2007). Searching for Evidence of Past Oceans on Venus, American Astronomical Society, DPS meeting #39, id.61.09; Bulletin of the American Astronomical Society, Vol. 39, p.540

3. Way, M. J.,et all (2016), Was Venus the first habitable world of our solar system?, Geophys. Res. Lett., 43, 8376–8383, doi:10.1002/2016GL069790.

4. Turbet, M., Bolmont, E., Chaverot, G. et al. Day–night cloud asymmetry prevents early oceans on Venus but not on Earth. Nature 598, 276–280 (2021). https://doi.org/10.1038/s41586-021-03873-w

5. Cornejo E, Abreu N, Komeili A. Compartmentalization and organelle formation in bacteria. Curr Opin Cell Biol. 2014 Feb;26:132-8. doi: 10.1016/j.ceb.2013.12.007. Epub 2014 Jan 16. PMID: 24440431; PMCID: PMC4318566.

6. Misra, A.K., Rowley, S.J., Zhou, J. et al. Biofinder detects biological remains in Green River fish fossils from Eocene epoch at video speed. Sci Rep 12, 10164 (2022). https://doi.org/10.1038/s41598-022-14410-8

7. Misra, A. et al (2021). Compact Color Biofinder (CoCoBi): Fast, Standoff, Sensitive Detection of Biomolecules and Polyaromatic Hydrocarbons for the Detection of Life. Applied Spectroscopy. 75. 000370282110339. DOI:10.1177/00037028211033911.

8. Beagle 2. https://en.wikipedia.org/wiki/Beagle_2 Accessed July 2, 2022


Comments on this entry are closed.

  • Mike Serfas July 5, 2022, 9:05

    Is it possible to do circular dichroism spectroscopy without entering the Venus atmosphere? Venus Express detected radio evidence of lightning strikes as common as Earth’s, and the Akatsuki orbiter reported seeing one lightning strike with its Lightning and Airglow Camera. ( https://www.nationalgeographic.com/science/article/
    does-lightning-strike-on-venus-mysterious-flash-help-solve-puzzle explains and links to the specifications). Unfortunately, that camera took five years to detect one strike. Nonetheless – could a future orbiter have a better camera that would detect multiple frequencies after many of the dark side lightning strikes and compare the circular polarization states? Would the density of airborne microbes or biochemicals be expected to be strong enough to have an effect?

    • Alex Tolley July 5, 2022, 17:25

      That question is well above m ability to answer. A paper on detecting plant life on Earth based on detecting circular polarization suggested that they could detect different plants because of the polarizing effect of chlorophyll. In the venus case, as they could detect algae in a lake, that would perhaps be relevant. However, note that this technique required that the plants had chlorophyll. With an unknown lifeform, we cannot assume such convenient large homochiral molecules and therefore this instrument might “look through” a Venusian tree right in front of it and not see it.

      Biosignatures of the Earth

      • Mike Serfas July 6, 2022, 18:23

        Thanks! This is a good reference. I should admit, thinking of going from something impressive to do with daylight to … doing it with lightning flashes may have been my wishful thinking getting the better of me.

        I’m thinking it’s not so much the size of the molecule as whether there is significant absorption from a single chiral molecule. And it’s admittedly rather optimistic to expect that from Venus also.

  • Andrew Palfreyman July 5, 2022, 9:21

    Why the aversion to the cheap and simple in situ optical microscope?

    • Alex Tolley July 5, 2022, 17:13

      +The simple answer is that bacteria, the life we are most likely to find, are too small to resolve with a light microscope. Bacteria are much smaller than eukaryote cells like yeast, or chlorella alga.

      bacteria: 0.2 – 2 uM
      yeast: 10 uM
      Chlorella 2 – 10 uM

      A light microscope uses light with an average wavelength of 550 nm (o.55 uM). This makes the bacteria, at best, look like blurred dots. And this is with a good quality microscope with a magnification up to 1000x. A small microscope with a magnification of 40-100x is not going to see these bugs at all, and certainly not with any hope of identifying them as life or not.

      Now one might hope that this might not be necessary if you can culture the bacteria, as is done in labs growing them on media. Liquid media might become cloudy, and solid media might show a colored patch. However, the vast majority of terrestrial bacteria cannot be cultured in the lab despite all our efforts and only knows what Venusian bugs might be like to grow.

      In a nutshell, a light microscope is not the instrument to use for bacteria. Now an electron microscope is a very different matter, but we cannot yet scale one down to the needed size and power for a space probe, even a Flagship class probe like Cassini.

      If we could be sure Venusian bacteria were based on the same biology as terrestrial bacteria, then a detector for DNA sequences would be the tool of choice. A nanopore DNA sequencer would be my choice, adapted to work in Venusian conditions, perhaps using microfluidics to extract and possibly replicate the sequences. Should this be the case, then DNA sequencing and analysis would be done on Earth once that had been established.

      As it is, I think that the VLF approach is a good choice for the first mission, albeit that even +ves for both the particle shape and organic content does not in any way rule out non-biological physical and chemical processes. It simply allows the go-ahead to start the next exploration phase. If there is no organic content in the particles (assuming that this is not a false -ve) then I would say that this mission reduces the chances that life on Venus exists. It may be that the probe missed a cloud with life, and other probes might be more successful. Is, a failure might be worth testing b repeating the experiment with a new probe of the same type if funding permits. Multiple failures would seem to end this line of experiments before the expensive balloon experiments are launched.

      • Michael July 6, 2022, 1:45

        Yes but if the blur wriggled about…I would put a microscope on the craft anyway.

        • Alex Tolley July 6, 2022, 8:14

          Assumptions about what you think of as life.

          Suppose you saw lots of dots jiggling about in the view field, would you assume the dots were alive. No. Brownian motion does that to inanimate particles. If you had the resolution to see the animals clearly swimming, that would be different, but that is not possible with the light microscope you have.

          If you see dots and they were not moving, would that indicate they were inanimate? Again no, because the life might be immobile, or have died while testing the sample.

          Far better to use what we have learned about the essentials of life to test for.

          Just think about what you would do if shown a clear lake on Earth and told you have just 5 minutes to determine if there is life in the lake or not (the time the first probe has to fall through the clouds and take readings). If you are allowed to take something back to a lab for analysis (sample return) what would you take?

          • Alex Tolley July 7, 2022, 11:16

            The answer today is just to take a sample of the water. There will be DNA fragments in that sample and they can be replicated and analyzed against the increasingly large genome databases. It was recently done in Scotland’s Loch Ness where a host of expected organisms were detected, but not Nessie.
            A news report about it: Loch Ness Contains No ‘Monster’ DNA, Say Scientists

      • Mike Serfas July 6, 2022, 18:33

        We should have NASA set people to work on scaling down every part of a near-field scanning optical microscope (NSOM) to the point where it weighs under a gram and costs under a dollar to mass produce … then drop a million of them on various planets of interest. Have them send an orbiter images from wherever water or sulfuric acid droplets (and contained microorganisms) can work their way on stage. Ideally we find life on Venus, but at the least we end up handing out disposable super-powerful microscopes in elementary school.

        • Alex Tolley July 7, 2022, 11:03

          I’ll settle for 30 g. ;) The NSOM has too high a resolution for most purposes and what you want is a super-lightweight optical microscope. Some years ago, MIT came up with a flat, folding design that just needed a tiny lens. The microscope was intended for use in the field in poor countries by doctors and others needing to highly magnify organisms. I think the cost was $1 per unit. Somewhere I think I still have the design. IMO this is the sort of technology for elementary schools as the children can look at what they find while they are outside collecting, rather than bringing the sample jars back to the classroom.

  • Geoffrey Hillend July 5, 2022, 15:22

    The first life on Earth may not have used photosynthesis, but there still would be some biosignature gases or waste products. Venus does not have any oxygen, so there can’t be any photosynthesis or bacteria at least not large amounts. Ultra violet light is also a problem in the upper atmosphere since there is no ozone layer in Venus atmosphere.

    I still think the idea of observing Venus with a high altitude balloon can give a lot of useful information about Venus atmosphere. A mass spectrometer could be used to detect any biosignature molecules, DNA or waste products and also the exact chemical composition of the upper atmosphere, wind speed, direction, etc

    • Alex Tolley July 5, 2022, 19:17

      Detection of gases in disequilibrium is slated for the balloon missions. Obviously, PH3 is a prime target they hope to confirm, preferably formed in the particles by life. If water can be split, then methanogenesis that produces CH4 could be the energy source for the bacteria. Also, bear in mind that there is anoxygenic photosynthesis that can trap sunlight, fix carbon, but not give off O2. It uses H2S instead of H2O, and elemental S is released. Green sulfur bacteria do this on Earth. Given the abundance of H2SO4, is it possible that H2S is available to be split by sunlight? Anoxygenic photosynthesis.

      • Geoffrey Hillend July 6, 2022, 18:06

        I looked up in google and found out that extremophiles don’t need oxygen or sunlight and can live in sulfuric acid H2SO4. Interesting. The main problem is getting to the right altitude. They would have to have evolved from the ground and became aloft. Hydrogen balloons are light but very explosive and there is a lot of lightning due to the friction of HsSO4 droplets between 40 and 65 kilometers. The extremophiles might be light enough to stay aloft, it’s the getting to that altitude is the problem. Evolving the element He seems rather far fetched.

        • Alex Tolley July 6, 2022, 20:48

          So there are quite a large number of bacteria species that are anaerobic, including the archaea. You may recall I have posted several essays on the early Earth biosphere, and how life may have started, including the positive energetics of methanogens in the deep ocean vents when the rock is ultramafic.

          As for organisms reaching that altitude, on Earth bacteria have been found almost as high as samples have been taken. For such organisms, their size makes the air much more like a viscous liquid and so they can easily be lofted by winds. You may recall the post by Robert Zubrin about such organisms being pushed off the top of the atmosphere and seeding Mars. (not impossible.)

          The atmosphere of Venus is far denser (CO2 vs N2/O2) and at high pressure. At the HZ level of the clouds, the particles, whether acid droplets or bacteria are in a temperate 1 bar atmosphere. If liquid droplets can remain suspended as clouds at that level, so can bacteria. (Bacteria are found in terrestrial clouds and contribute to rain formation.)

          The controversial issue is whether life ever evolved on Venus (or arrived from elsewhere) and then was able to evolve to survive in the very extreme pH conditions currently in the clouds in the HZ. Recall that we had no idea about terrestrial extremophiles until relatively recently (the 1980s). So while I remain skeptical, I wouldn’t rule it out, and I would be delighted if it proved to be the case. Venusian life, like any non-terrestrial life, would be a goldmine for biology and the related industries. Just think of all those sci-fi shows where a corporation wants to get exclusive control of such alien life. Weyland-Yutani ring a bell?) Given the relatively low costs of Venus atmosphere missions, it seems worth at least looking for.

        • Geoffrey Hillend July 7, 2022, 3:10

          Thinking about this further one needs oxygen in order to for hydrogen to burn and an explosion.

  • Adam Crowl July 5, 2022, 19:26

    Hi Alex
    Nice write up. What do you make of the suggestion of ammonia in the clouds of Venus?
    Production of ammonia makes Venusian clouds habitable and explains observed cloud-level chemical anomalies
    …another provocative piece by Bains et al.

    • Alex Tolley July 5, 2022, 20:54

      Hi Adam,
      If true, that is one of the pieces the VLF team is hoping for as a way to neutralize the extremely low pH of the H2SO4 cloud particles. The first mission has no way to test this, other than some pH measurements that may be indicative. NH3 would be a good source of needed N for biological molecules as we know them too.

      I hope the mission gets underway next year and succeeds at least in demonstrating a small probe can do planetary science successfully, whatever the data tells us.

  • Ivan Vuletich July 5, 2022, 20:36

    As a non-biologist, shouldn’t indications of movement, growth and reproduction be added to your list of 5 key analyses? While non definitive in its own right, combined with one of the others it would almost be a slam dunk.

  • Afterthought July 5, 2022, 23:20

    I’m more in the “put life” rather than “find life” school of budgeting.

    • Alex Tolley July 6, 2022, 8:18

      So I show you an acid stream from leached mine tailings. Your task is to restore the stream so that it is definitely living. How do you remediate the stream?

      It is a task like terraforming on a microscale, isn’t it?

  • Michael July 6, 2022, 8:43

    Here is a nice article on possible constraints on a biosphere at Venus.


    • Alex Tolley July 6, 2022, 13:22

      Interesting details that might narrow the HZ at least by reducing the upper bound due to high UV exposure.

  • Alex Tolley July 6, 2022, 9:38

    I am a fan of mid-20th century SciFi tv and movies. Of particular relevance here are the 1953 BBC tv drama miniseries, “The Quatermass Experiment”, and the 1951 movie “The Thing From Another World”.

    Both were made before the discovery of the structure of DNA in 1953, and within a decade of Schroedinger’s famous essay “What is Life?” (1944).

    While drama is key, one should note how primitive the capabilities of the doctors and scientists were in those 2 examples. In the case of TQE, the doctor looking after the surviving astronaut Victor Carroon, could only do simple blood tests and stare down a microscope. Despite Carroon’s skin and flesh showing obvious signs of changes, he was unable to do anything to understand the changes. Similarly, in TTFAW, with a team of top scientists under Carrington at the North Pole, none were able to do much more than inspect the torn-off arm of the Martian, and note its plant-like characteristics.

    When I was at university in the early 1970s, it was barely 2 decades after Watson and Cricks elucidation of DNA. We knew very little about genes (the university had a classic genetics course), proteins were being painfully slowly sequenced, the RNA theory of memory storage was a viable hypothesis (!), biotech was just getting started in the US, and the expensive sequencing of the human genome was decades in the future. Computers were mainframes that needed punched cards to program.

    The understanding of biology and the tools we currently have would be science fiction back then. Presented with even a few cells of the crashed Martian, or the skin of Carroon, we would be able to tell a lot more about the nature of the Martian and Carroon’s apparent traumatized state.

    When I compare more sci-fi shows and movies, the scientific investigations are just depicted as computer displays showing, apparently, everything the protagonists would want to know. Alien bug taking over a crew member, no problem. An alien species has been found, the computer will analyze it until it escapes to kill the crew because biohazard precautions were not seriously taken.

    With alien life, we are in some regards caught in between these 2 eras. We have a lot of knowledge about terrestrial life, but we are forced to rephrase Schroedinger’s 1944 question as “What is Alien Life?”. We should be so lucky to make as good a guess at the hypothetical nature of the storage molecule as he did, but now with the knowledge we have of DNA. We have a panoply of tools to investigate any putative life form, some of which will work, and others that do not as they are based on terrestrial life. We might be as in the dark as the scientists in “The Andromeda Strain” (1971), or we might find that alien life is not so fundamentally different from terrestrial life. The details may be different, but the fundamentals are recognizable. If so, over time, we will be able to adapt our tools to investigate this alien life, which will make our “toolbox” even better to investigate other alien life as we come across it.

  • Spaceman July 7, 2022, 12:36

    @Alex Tolley:

    Each of the 20 “essential” amino acids has a different R group. Thinking about the diversity of possible carbon-based life elsewhere in the Universe, I wonder about how much variety there might be in terms of the number of different amino acid R groups that such eco-life might utilize for protein-making. There are so-called non-proteinogenic amino acids like theanine (I just bought some cold brew coffee that has theanine as an added ingredient lol). From a computational synthetic organic chemistry standpoint, is there a way to calculate how many types of R groups could exist on a polypeptide of a certain length??

    • Alex Tolley July 7, 2022, 13:48

      The possible number of R groups is vast – it just depends on how many carbons you allow. To be functional in proteins I would think the carbon number has to limited in size as if they are too large they will interfere with their neighboring and cross-linked AAs in the protein. Looking at the 20 life uses, the longest linear R-group c-c chain is 5 carbons (lysine). There are more carbons but either the chain is broken with a N or S, or the chain ends with aromatic groups. One could probably work out the size of the largest AAs as a possible limiting factor.

      There is a chemistry database out there that could give you estimates based on the constraints you put on the R groups. Sorry, I don’t have the link.

      As you know, there have been experiments to add new amino acids to proteins by tailoring the tRNA and the genetic code in model bacteria.

  • Robin Datta July 7, 2022, 13:25

    Alien life may or may not resemble ours, with an entirely different separate origin or a separate origin constrained to be similar by physical, chemical, and other influences. Convecgence and divergence may make the different similar and the similar different, facilitating or impeding detection.

    More advanced and/or specialized detecting modalities may more easily overlook significant features.

  • John Donaldson July 7, 2022, 17:58

    Not too keen on bringing exotic biology back to Earth. A mistake in transport could end up killing us.

  • Joe H. July 11, 2022, 21:02

    Since the distance between stars is not constant this will be a factor in any interstellar mission. Planning a flyby or an orbit of an exo-planet will require artificial intelligence of the highest order.

  • ljk July 26, 2022, 16:52

    60 years ago, the first American attempt to explore Venus by space probe:


    My CD essay on Mariner 1 and those other pioneers of interplanetary exploration here:


  • ljk July 26, 2022, 16:53

    New updates on the search for life on Venus here…


  • ljk July 27, 2022, 12:40

    Mission Architecture to Characterize Habitability of Venus Cloud Layers via an Aerial Platform

    by Rachana Agrawal 1,*ORCID,Weston P. Buchanan 1ORCID,Archit Arora 1,Athul P. Girija 1ORCID,Maxim De Jong 2,Sara Seager 3,Janusz J. Petkowski 3ORCID,Sarag J. Saikia 4,Christopher E. Carr 5ORCID,David H. Grinspoon 6ORCID,James M. Longuski 1 andon behalf of Venus Life Finder Mission Team
    School of Aeronautics and Astronautics, Purdue University, West Lafayette, IN 47907, USA
    Thin Red Line Aerospace Ltd., Chilliwack, BC V2R 5M3, Canada
    Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
    Spacefaring Technologies Pvt. Ltd., Bengaluru 560066, India
    School of Aerospace Engineering and School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA 30332, USA
    Planetary Science Institute, 1700 East Fort Lowell, Suite 106, Tucson, AZ 85719-2395, USA
    Author to whom correspondence should be addressed.
    Academic Editor: Pierre Rochus
    Aerospace 2022, 9(7), 359; https://doi.org/10.3390/aerospace9070359
    Received: 7 June 2022 / Revised: 27 June 2022 / Accepted: 2 July 2022 / Published: 6 July 2022

    (This article belongs to the Special Issue The Search for Signs of Life on Venus: Science Objectives and Mission Designs)

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    Venus is known for its extreme surface temperature and its sulfuric acid clouds. But the cloud layers on Venus have similar temperature and pressure conditions to those on the surface of Earth and are conjectured to be a possible habitat for microscopic life forms. We propose a mission concept to explore the clouds of Venus for up to 30 days to evaluate habitability and search for signs of life. The baseline mission targets a 2026 launch opportunity. A super-pressure variable float altitude balloon aerobot cycles between the altitudes of 48 and 60 km, i.e., primarily traversing the lower, middle, and part of the upper cloud layers.

    The instrument suite is carried by a gondola design derived from the Pioneer Venus Large Probe pressure vessel. The aerobot transmits data via an orbiter relay combined with a direct-to-Earth link. The orbiter is captured into a 6-h retrograde orbit with a low, roughly 170-degree, inclination. The total mass of the orbiter and entry probe is estimated to be 640 kg.

    An alternate concept for a constant float altitude balloon is also discussed as a lower complexity option compared to the variable float altitude version. The proposed mission would complement other planned missions and could help elucidate the limits of habitability and the role of unknown chemistry or possibly life itself in the Venus atmosphere.


    9. Conclusions

    We propose a balloon mission to explore the cloud deck of Venus in search of signs of life and to investigate the habitability of cloud particles. The balloon explores the cloud region from 48 to 60 km—completing the baseline mission after two weeks, with the possibility of extended operations lasting up to one month. Science data is returned via an orbiting relay and direct-to-Earth transmission. The balloon deploys miniature probes at select times during its flight operations to provide spatial and temporal diversity in acquired data.

    The science payload is a mix of novel high TRL and low TRL instruments. The unique astrobiology-focused goals of the mission, combined with the challenging operational environment, require the capability advancement of instruments that have not yet been applied to planetary exploration. Such instruments, carried by a variable float-altitude balloon, would enable the characterization of habitability and poorly understood phenomena in the Venus clouds and could possibly result in the discovery of signs of life at Venus—which, if confirmed, would be among the most significant events in human history.