Life on Venus?

[KerikBalm]

https://en.wikipedia.org/wiki/Water_activity#Selected_aw_values

On earth, we don't observe any life in areas with an a_w less than about 0.6. 

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4438321/

https://sfamjournals.onlinelibrary.wiley.com/doi/full/10.1111/1462-2920.12598

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1693405/

Which has previously been brought up with regards to the suitability of the putatve salty brines on Mars: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7358355/

Life on earth simply does not appear to be able to function with an a_w of less than 0.6. Given the very dry conditions in some places such as the atacama and Sahara deserts, and other hypersaline environments (some of which have extremophiles, others are even saltier and don't seem to have life), if life on Eart hcould have adapted to such low water activity, it should have already done so.

Its extremely unlikely that it would be able to do so from small amounts of microbes on the surface of a probe that was not assembled in those extreme environments (favoring non-extremophile contamination), followed by a long period in space subject to ionizing radiation without conditions allowing active DNA repait,  to be shed in small amounts on a very different environment, as opposed to the gradual transitions that we observe in earth environments.

I think the possibility of contamination from Earth is overblown for Mars, and especially for Venus. Europa and Enceledus on the other hand... I'm not sure how briny the subsurface water is there, it may be quite mild for Earth life.

The atmoshere of Venus is very very dry, with a very low water activity: https://www.liebertpub.com/doi/10.1089/ast.2020.2244#:~:text=2.3.&text=Venusian water activity is much lower than any analogous habitat on Earth.&text=The habitat inside liquid droplets,of liquid water (15%).

Its not contamination from Earth probes, and I doubt its life. If it is life, it must have fundamentally different biochemistry, because Earth life's biochemistry does not appear capable of living in such low a_w conditions, despite prolonged contact with such conditions, and all manner of intermediate environments to facilitate the evolutionary transition.

Edited September 16, 2020 by KerikBalm

[Guest]

Atacama does have extremophiles. Although, they depend on very rare events when it does rain, and they're not quite "alive" when they're dry. Indeed, such cases tend to inspire discussion about what it actually means to be alive. The search for life had focused on finding water for a very good reason. 

Of course, anything found on Venus will have different biochemistry. As I said, whatever we find, whether life, chemistry, or something inbetween, it'll be seriously weird. If it's life, it should still involve water in some way, but since it's so rare, it would have to make an effort keep it in. Maybe even synthesize it itself (maybe phosphine could be a byproduct of such a process?). Water can have some funny behavior if bound up in something, I'm not sure if Venus Express would have shown it if the clouds were full of microbes with a death-grip on any water molecules.

Either way, we need to confirm phosphine with more remote observation, and then we need a probe on site. Ideally, some sort of blimp with a propulsion system and as many experiments as we can hang off it.

Edited September 16, 2020 by Guest

[kerbiloid]

Venus never rains.

[cubinator]

4 minutes ago, kerbiloid said:

Venus never rains.

Sure it does. It's just H₂S, not water.

[sevenperforce]

13 minutes ago, Dragon01 said:

As I said, whatever we find, whether life, chemistry, or something inbetween, it'll be seriously weird. If it's life, it should still involve water in some way, but since it's so rare, it would have to make an effort keep it in.

Life doesn't need water. You could rather easily have life which uses liquid hydrogen sulfide or sulfuric acid or pretty much any covalent molecule as its primary solvent and metabolic base. It's easier if it's a diamagnetic molecule like hydrogen sulfide so that you can get hydrogen bonding.

My chemistry-fu is probably my area of greatest scientific weakness, but I'm sure that someone with better chemistry chops than myself could come up with a closed-loop metabolic pathway involving phosphoric acid, phosphine, hydrogen sulfide, carbon dioxide, sulfur dioxide, and some sort of acid anhydride. 

The bond energy for carbon dioxide is 4.2 kJ per mole, while the bond energy for sulfur dioxide is on the order of 1 kJ per mole, so if you have life that is based on the reduction of sulfur dioxide to carbon dioxide there's a lot of potential energy there.

[Guest]

The thing is, it's not just metabolic pathways. Life needs more than that. Most notably, it needs to be happening in something. That means, some sort of solvent. Water is a really good candidate because of the aforementioned weird behavior when in contact with the other molecules, not to mention being highly polar and being able to create hydrogen bonds. I could come up with a closed loop pathway, but not make it happen without water. Most notably, acids are only really acids when disassociated in, guess what, water. The key feature that makes acid an acid is the fact that is disassociates, releasing H+ ions into the solution and binding OH- ions, shifting the balance towards the former. Out of solution, ionic bonds are very strong, and an anhydrous acid is a very different beast from one that's in water.

HS cannot form hydrogen bonds, it's not polar enough. They're only a thing with water, HF (one bond per molecule, can only form chains) and ammonia (inconvenient shape, could possibly work, but only in extremely low temperatures). On Venus, water is pretty much the only option.

[cubinator]

Water is special because it's a solvent for SO MUCH stuff. It's ridiculous. Anything you want for life, anything you need, it dissolves in water. Other liquids like methane, ammonia, sulfuric acid, etc. all have certain molecules that dissolve in them, but the question is whether you can get enough "life ingredients" dissolved in a liquid that isn't water that the ingredients can make a recipe, and create a whole organism. We don't know of anything that's quite as good as water for that.

[Guest]

The things that don't dissolve in water are important, too.  The whole deal with cell membranes works based on what happens when you have a mixed water-lipid phase. We're mostly water, but a good chunk of us that isn't water consists of yet another solvent, this time nonpolar.

I think it might be possible to invert that arrangement, but you'll need water either way. It would be trapped in membranes and micelles, with stuff that needs a polar solvent inside (that, and all hydrogen bond magic happening in there). This actually sounds like a nice setup for a Venusian organism, as it would prevent the water from getting anywhere without getting through the nonpolar part.

[K^2]

One of the speculations has been that small droplets of water can form occasionally and be brought up to cloud layer with air currents. If some airborne spores exist, they can be dormant until they encounter such a droplet, then use it to reproduce until the droplet dries up, and form new spores. This is plausible with what we know of atmosphere of Venus and with types of life we know on Earth. Whether this is viable long term and if it could have evolved from ocean life when the oceans evaporated remains entirely unknown, of course, but that's a way Venus could have life without needing to invent a new solvent.

Of course, if this is the case, the cloud cities start sounding like a really bad idea. It's one thing to deal with scarcity of some resources, and completely another if atmosphere is filled with what's basically Venusian anthrax. Life that's all about capitalizing on any moisture droplets it finds is going to do bad things to human lungs.

[Scotius]

Oh, yes - that's what we need. Planet with atmosphere full of lung-eating bacteria. Like one Earth wasn't enough. Thanks 2020!

[kerbiloid]

"Sometimes a phosphine is just a phosphine."

[KerikBalm]

15 hours ago, Dragon01 said:

Of course, anything found on Venus will have different biochemistry. As I said, whatever we find, whether life, chemistry, or something inbetween, it'll be seriously weird.

but you said

On 9/14/2020 at 10:03 PM, Dragon01 said:

This actually got me thinking. We know terrestrial life can make phosphine, and that there are species that could survive in the atmosphere of Venus. Were the Venera probes decontaminated? I'm not sure if Soviets had an equivalent to Planetary Protection Officer at the time, and even if they did, they knew Venus was a hellhole back then, and extremophiles were poorly researched at the time. I wonder, what are the chances that one of those hitched a ride in one of the parachute containers, or on a balloon probe, and, having found a perfect environment, spread far enough for its metabolites to show up? It's a rather disturbing thought. 

I would say definitely not. That would lower the known a_w range of earth-life from 0.6 to about 0.15, among other issues.

On 9/14/2020 at 11:53 PM, Dragon01 said:

Remember, we know that there are bacteria on Earth that could survive in conditions similar to the upper atmosphere of Venus.

Define "similar", and define "survive". I would not define metabolically inactive spores that would still be viable if returned to milder conditions as capable of surviving in those conditions. If the life form cannot reproduce under those conditions, it cannot survive (in the long term) under those conditions. In particular on Venus, the reproduction rate needs to be fairly high to account for mixing of the upper atmosphere with the lower atmosphere where it will certainly be destroyed.

We know of no life on Earth that can replicate itself at anywhere even close to the a_w range of Venus. So we know of no life capable of surviving in similar conditions to the upper atmosphere of Venus.

On 9/14/2020 at 11:53 PM, Dragon01 said:

Either way, a bacteria in an unconstrained environment could grow rapidly

Define "unconstrained". In this case, the environment itself is a constraint. In my review of a_w limits of life, it seems most life lives in an a_w of 0.9-1.0, and although some life can still replicate at a_ws much lower, the division rate starts dropping by orders of magnitude. Growth is very very very slow around an a_w of 0.6 for all known Earth-life.

15 hours ago, Dragon01 said:

Atacama does have extremophiles. Although, they depend on very rare events when it does rain, and they're not quite "alive" when they're dry. Indeed, such cases tend to inspire discussion about what it actually means to be alive.

For the purposes of this discussion, if they cannot replicate in those conditions, they cannot survive long term in those conditions. There are some places where the atacama desert surface samples come back seemingly sterile. What is there is thought to have blown in. On the surface without active DNA repair (thus active metabolism), UV light renders many spores non-viable rapidly. Of course just a mm or two under the surface can prevent that. Some stuff is blown in, other stuff can wait it out for the very rare rain or at least elevated humidity.

In the worst parts of the atacama desert, the humidity / a_w is about 3x better than the best case for Venus. The atacama desert is an oasis in comparison. If we don't find metabolically active life in the worst part of the atacama, then we won't find any life with earth-similar biochemistry on Venus. Cryptobiosis isn't good enough, especially when relying on suspension in droplets/aerosols to stay above the kill conditions. Even favorable circulation cells have mixing, and survival will depend on reproducing faster than the average lifetime of a particle in suspension. They cannot wait very long for better conditions, they must be metabolically active a significant portion of the time.

Earth-life won't do it if the best case situation for the worst of the atacama is a state of cryptobiosis most of the time.

14 hours ago, Dragon01 said:

Water is a really good candidate because of the aforementioned weird behavior when in contact with the other molecules, not to mention being highly polar and being able to create hydrogen bonds.

Which is one reason that a_w is very important. DNA's structure depends on said H-bonds. It will start to lose its ordered structure at an a_w of less than about 0.55. Such an a_w is wildly optimistic under any scenario for venusian clouds.

I'm not saying there can't be life in the clouds of Venus, I'm saying it can't have Earth-like biochemistry. If it is there, it can't be contamination from Earth.

6 hours ago, K^2 said:

One of the speculations has been that small droplets of water can form occasionally and be brought up to cloud layer with air currents. If some airborne spores exist, they can be dormant until they encounter such a droplet, then use it to reproduce until the droplet dries up, and form new spores. This is plausible with what we know of atmosphere of Venus and with types of life we know on Earth. Whether this is viable long term and if it could have evolved from ocean life when the oceans evaporated remains entirely unknown, of course, but that's a way Venus could have life without needing to invent a new solvent.

That is what the authors of this phosphine observation propose in a separate publication:

https://www.liebertpub.com/doi/full/10.1089/ast.2020.2244  (note the author overlap with https://www.nature.com/articles/s41550-020-1174-4#MOESM1 )

However, they pull a little switcheroo in their speculation, and switch from talking about water activity to water content. They start talking about the water content of droplets that are by their own admission, only 15% water - and thus have an a_w of about 0.15, which is 1/4th what anything on Earth has been observed to reproduce in. So this reproduction in droplets is plausible for Earth-life in water droplets on Earth - but it does not seem to be plausible for Earthlife in droplets with a composition similar to what we see on Venus. Metabolically active microbes in Earth's atmosphere (for which its still unclear if there is significant sustained replication up there, or if the airborne biosphere is basically due to ground-based life being swept up but surviving in the short-term)

6 hours ago, K^2 said:

Of course, if this is the case, the cloud cities start sounding like a really bad idea. It's one thing to deal with scarcity of some resources, and completely another if atmosphere is filled with what's basically Venusian anthrax. Life that's all about capitalizing on any moisture droplets it finds is going to do bad things to human lungs.

Well, based on the literature research I've done in the past couple days, the earth-life that does survive at low a_w does not survive at high a_w. Anything surviving in a droplet that is 15% water, and 85% H2SO4 is going to find that human lungs are extremely basic, with very different hydrogen bonding properties, that is very very very likely going to gum up all the works and kill it.

On top of that, as I mentioned, the biochemistries would have to be so different, it won't know what to do with the biomolecules it does find.

I wouldn't worry about it.

[Guest]

15 minutes ago, KerikBalm said:

I wouldn't worry about it.

Do note, just because the Venusian microbe would die doesn't mean it still wouldn't do damage. It's not just lungs, either, for something like that, even skin would appear to be one big glob of water. Although breathing sulfuric acid would, too, so the clouds cities would have to be enclosed, anyway.

When I speculated about Venera contamination, I was under impression that water content of Venusian clouds was still up in the air. It does appear Venus Express measured it. Of course, this assumes our models, derived from Venus Express data, are accurate. Perhaps there's more water out there than we thought, for example lower down in atmosphere. That mission wasn't particularly expecting to find much water in first place, and being an orbiter, was limited in what it could see from up there. As I said, we could really use a blimp probing those clouds.

[KerikBalm]

3 minutes ago, Dragon01 said:

Do note, just because the Venusian microbe would die doesn't mean it still wouldn't do damage. It's not just lungs, either, for something like that, even skin would appear to be one big glob of water. Although breathing sulfuric acid would, too, so the clouds cities would have to be enclosed, anyway.

They'd have to be enclosed, but if there is a tiny leak, you don't neccessarily have to rush to contain it. On the other hand, if it contains a deadly pathogen, you could be in big trouble.

A big glob of water for something not used to it can be deadly. A very simple example is dumping a sea-going fish into fresh water...

https://sfamjournals.onlinelibrary.wiley.com/doi/full/10.1111/1462-2920.12598

Quote

There are only reports of cell division for between 20 and 30 microbial species or communities at ≤ 0.690 a_w ([refs snipped]). Whereas all of these species are obligately xerophilic eukaryotes or obligately halophilic prokaryotes, which have low rates of cell division – or are incapable of growth – close to a water activity of 1, the ultimate limit for multiplication of even the most resilient strains appears to be ∼0.61 a_w

The organisms we know of that can tolerate low a_w fare very poorly when put in an a_w of close to 1. The even more extreme conditions of Venus would suggest that any Venusian organism would be killed by the salt, pH and water content of our bodies.

3 minutes ago, Dragon01 said:

When I speculated about Venera contamination, I was under impression that water content of Venusian clouds was still up in the air. It does appear Venus Express measured it. Of course, this assumes our models, derived from Venus Express data, are accurate. Perhaps there's more water out there than we thought, for example lower down in atmosphere. That mission wasn't particularly expecting to find much water in first place, and being an orbiter, was limited in what it could see from up there. As I said, we could really use a blimp probing those clouds.

I'm in favor of more exploration. I just think its

#1 Nearly impossible that there is life resembling Earth-based life/that is contamination from Earth/that poses a threat to Earthly organisms

#2 Unlikely that there is life on Venus, but if so it will be very different from ours and not even have DNA/RNA

#3 Very likely that we will learn something new about Venus or chemistry.

 

[Space Nerd]

18 hours ago, cubinator said:

Sure it does. It's just H₂S, not water.

You mean sulfuric acid?

[K^2]

3 hours ago, KerikBalm said:

Well, based on the literature research I've done in the past couple days, the earth-life that does survive at low a_w does not survive at high a_w. Anything surviving in a droplet that is 15% water, and 85% H2SO4 is going to find that human lungs are extremely basic, with very different hydrogen bonding properties, that is very very very likely going to gum up all the works and kill it.

Hey, who are you calling basic? 

But yeah, good point. They say "water droplet", but in Venusian atmosphere these droplets would need to be diluted with more water before you can use them safely for battery acid.

It does occur to me that, for example, DNA will certainly be completely destroyed by this pH level. I know terrestrial extremophiles generally adapt their biochem to environment, but in this case, I'm not sure that's even possible if this life was to evolve from oceans. Seems like the only way to combat it is a cell wall that can withstand the environment and some powerful proton pumps. I wonder if that's even viable, and whether something like that, if existed, would be less picky about pH.

Edited September 17, 2020 by K^2

[magnemoe]

20 hours ago, Dragon01 said:

Atacama does have extremophiles. Although, they depend on very rare events when it does rain, and they're not quite "alive" when they're dry. Indeed, such cases tend to inspire discussion about what it actually means to be alive. The search for life had focused on finding water for a very good reason. 

Of course, anything found on Venus will have different biochemistry. As I said, whatever we find, whether life, chemistry, or something inbetween, it'll be seriously weird. If it's life, it should still involve water in some way, but since it's so rare, it would have to make an effort keep it in. Maybe even synthesize it itself (maybe phosphine could be a byproduct of such a process?). Water can have some funny behavior if bound up in something, I'm not sure if Venus Express would have shown it if the clouds were full of microbes with a death-grip on any water molecules.

Either way, we need to confirm phosphine with more remote observation, and then we need a probe on site. Ideally, some sort of blimp with a propulsion system and as many experiments as we can hang off it.

In an desert you can go dormant for decades waiting for water, this works often enough, mostly you get eaten or other stuff but its no hurry. 
In venus atmosphere you have the risk of going too deep so you will have to reproduce often enough to compensate. 
Now I assume we have enough data about the weather on Venus to have some estimates here obviously depending on how deep it can survive. 
 

[Scotius]

What about colonial organisms? I'm imagining something akin to a soap bubble filled with hydrogen. Porous walls constructed from a layer of hydrophilic (maybe even dead) cells. Inside layer is made of living cells that absorb and store water that soaks through the outer layer, produce hydrogen to keep the colony afloat and replicate.

[Guest]

It'd be easier to float with the wind, which, IIRC, can be quite fierce on Venus. 

[Scotius]

8 minutes ago, Dragon01 said:

It'd be easier to float with the wind, which, IIRC, can be quite fierce on Venus. 

Could still work. Bubble doesn't have to be spherical - it can very well have an aerodynamic shape.

[sevenperforce]

13 hours ago, K^2 said:

It's one thing to deal with scarcity of some resources, and completely another if atmosphere is filled with what's basically Venusian anthrax. Life that's all about capitalizing on any moisture droplets it finds is going to do bad things to human lungs.

I'm reminded of Doctor Who....

1 hour ago, Scotius said:

What about colonial organisms? I'm imagining something akin to a soap bubble filled with hydrogen. Porous walls constructed from a layer of hydrophilic (maybe even dead) cells. Inside layer is made of living cells that absorb and store water that soaks through the outer layer, produce hydrogen to keep the colony afloat and replicate.

Oxygen is a lifting gas on Venus.

[kerbiloid]

2 hours ago, Scotius said:

Could still work. Bubble doesn't have to be spherical - it can very well have an aerodynamic shape.

+1
 

Spoiler

 

[coyotesfrontier]

Assuming we're able to conclusively prove life exists on Venus, how will this affect Earth culturally? World religions are going to have to respond to it, and we'd have to rethink our place in the universe. This also might depend on the nature of the life. If it turns out to have appeared completely separately from Earth, this means that life must be extremely common in the universe, giving an even greater cultural impact. If it turns out to have come from Earth via panspermia, there'd be a lesser effect as it wouldn't prove much about the rarity of life.

Edited September 17, 2020 by coyotesfrontier

[wumpus]

7 minutes ago, coyotesfrontier said:

Assuming we're able to conclusively prove life exists on Venus, how will this affect Earth culturally? World religions are going to have to respond to it, and we'd have to rethink our place in the universe. This also might depend on the nature of the life. If it turns out to have appeared completely separately from Earth, this means that life must be extremely common in the universe, giving an even greater cultural impact. If it turns out to have come from Earth via panspermia, there'd be a lesser effect as it wouldn't prove much about the rarity of life.

Good luck showing that life emerged on Venus: it isn't a place I'd expect to find any fossils.  Similarly, I'm not aware of any era in time that fossilization was possible that doesn't contain evidence of life.  Earth life could have easily been seeded by Venus (or any other planet), especially if both planets were under asteroid bombardment (I'm unclear about when this happened vs. when life appeared, but it really only requires one meteror with the exact right exit velocity of debris).

Panspermia across solar systems would be different from panspermia across planets.  Unless you want to posit that the missing dark matter is extra globs of life being flung through the universe where we assume there is only hydrogen gas.  I can't imagine how much mass it would take to typically seed a galaxy with life (especially if it has to get to a solar system with the first few hundred million years).

[sevenperforce]

16 minutes ago, coyotesfrontier said:

Assuming we're able to conclusively prove life exists on Venus, how will this affect Earth culturally? World religions are going to have to respond to it, and we'd have to rethink our place in the universe.

No matter how conclusively it is proven that the life originated independently, the sorts of religious groups which deny deep time and think humans put saddles on T. rex will inevitably claim "there are other interpretations".