Humans have sent space probes to Venus, and the Soviet ones weren't sterilized. It was thought there was no need, given the extreme environment there.
This bacteria is introduced to an environment that has all it needs to spread quickly. There's absolutely nothing out there that it has to compete with. There's nothing out there consuming it or infecting it or otherwise inhibiting its growth other than a lack of whatever nutrient it consumes.
Rabbits went from 0 to over 200 million in under 200 years in Australia, and that's with snakes and disease. Apparently they spread across the continent in just 50 years.[1] Rabbits generally reproduce at a small fraction of the rate of bacteria, although exceptions exist.
Note: I'm not saying humans definitely introduced bacteria to Venus and that's the source. I'm saying if conditions are by some chance ideal, and these things are apparently thriving in the atmosphere, it shouldn't be hard to spread across the planet incredibly fast.
[1] https://www.nationalgeographic.org/article/how-european-rabb...
Hopefully if they can get a probe out there they would be able to tell definitively if it was Soviet contamination or not, although I'm not sure how they would be able to do that. I could see them ruling it out (some entirely different DNA structure or something) but not sure how they'd say 100% that it was Soviet in origin.
Even if spores did survive the space trip (actually quite plausible, [0], venus trip is ~110 days), the atmosphere is extremely dessicating and acidic (SO2, SO3, H2SO4), and the ground is too hot for any known life. The dessication and osmotic pressure is the real kicker. It's very unlikely spores would germinate without rehydration.
[0] https://www.nasa.gov/mission_pages/station/research/news/eu_...
[1] https://www.nytimes.com/1966/03/06/archives/soviet-says-venu...
So not only do we have no good explanation for phosphine, we do not have a good explanation for the unknown absorbers. Well, we do have one good explanation although it seemed unlikely and that is life. Given that this is second effect that could be explained with microbes I feel it adds that much more weight to the theory.
You would have considerable choice; it would be quite obvious whether they'd been on a separate evolutionary trajectory for billions of years or not. That's still the boring outcome, though; not related to us at all would be far more interesting.
Very, very unlikely outcome.
However, happening on two adjacent planets would really affect our estimations of the likelihood of abiogenesis.
Life could have arisen on Earth much later than it did and we could still have been around to see it (or if not us, something like us) so the anthropic principle doesn't apply here. The fact that it arose so early is meaningful.
I would assume it is DNA-based life. It would be a major surprise if it would be RNA-based life or something not resembling our tree of life.
DNA and RNA: Perhaps they are inevitable, and any lifeforms have the same molecules and bases. Perhaps some lifeform can use only the methylated versions? Is ribose inevitable? Is 3 bases per codon inevitable? But I think there is a chance for inevitability.
The list of amino acids is somewhat random. We use 20, Some bacteria use a 1 or 2 more. And we can transform in place the amino acid inside a protein into another amino acid. I expect a similar list of 20+-5 amino acids. A perfect coincidence would be too hard, but it is not even true for terrestrial life.
The most interesting part is the Genetic Code https://en.wikipedia.org/wiki/Genetic_code that translate the 4^3=64 combinations of bases in the DNA to the 20 amino acids. As far as we know it is random. It has some internal structure, for example the code is mostly like 16 blocks to encode 15 amino acids and a stop signal, and a few tweaks here and there to break some block to encode the other 5 amino acids. But as far as we know there are no reasons to choose each block as us.
Some bacteria use versions with small tweaks, with one or two changes, so we know it if possible to change it, but very difficult to make a total rewrite.
If the life out there use the same Genetic Code (with a few tweaks) it is almost sure it is related to us.
https://www.sciencedirect.com/science/article/abs/pii/S00225...
Now, I'm not an expert or even an advanced layperson in this area, so I won't attempt to speak to the validity of the idea. I merely found the argument interesting at the time.
First they propose a genetic code that is totally unrelated to the current one. It can be perfectly the table of a totally different lifeform. The transition they propose looks too difficult, almost impossible.
Probably we had a transition from RNA to DNA a loooong time ago, but they have a 1 to 1 translation, and the intermediate steps look useful. But no one is sure anyway.
They propose a change where almost all the table changes and almost all the internal structure of the table change.
It is very strange that they have 20 amino acids and no stop code. A proposal with 19 amino acids and a stop code looks more sensible. We know that it is possible to add new amino acids to the table (with enough time). I think the main problem is that using 19 amino acids and a stop code breaks the magical part of predicting the number 20 with pencil and paper.
To make the table work, you need the correct transfer-RNA. To get all the symmetries in their model you need to be really lucky. In the block model of 15+1 you any random selection of tRNA is fine if it ignore the last base.
Another big problem is that they predict that half of the proteins would have been constructed backward. But as they say this make proteins not fold correctly. They try to avoid the problem using palindromic proteins, that is not supported by evidence.
“Match” means “match”. Not “similar structure and behavior”. If it is the same DNA then the only compelling explanation is that it is from the same origin.
How likely is it that alien life would also use DNA?
So if something is an exact match it is evident that they came from the same time and place (within some reasonable window). The origin would implicitly be Earth in the 1960s.
In any case it makes it much less interesting, as it implies same origin.
Implies but does not prove, I should add, of course.
This of course does not account for other differences such as the rate at which microbes are transported into Earth's atmosphere, and whether that possibly habitable layer on Venus is stable enough to sustain a population.
1. Bombarded mars with junk (everything from the astroid belt and some rocks from the kuipler belt) to raise its mass to somewhat earth level. We'd have to be careful not to mess up Mars's orbit too much. 2. Slurp some of venus's thick atmosphere into a massive space tanker 3. Dump the atmosphere onto Mars++ 4. Let time and some engineered bacteria/plants clean up the mess
That's my long term goal if I become immortal.
That doesn’t rule out a ‘contamination’. But considering this is just another observation in a long line of interesting data I think makes it less likely.
The Wikipedia page on Venus's atmosphere suggests that at that altitude Venus's atmosphere is a sulphuric acid haze at 110°C and about 2atm of pressure, which, even if there was something to walk on, doesn't sound like you'd be able to walk around with just an oxygen supply for very long.
https://selenianboondocks.com/2013/11/venus-isru-what-do-we-...
Which as far as I can tell isn't terrible if you don't breath it in and if you do the official allowed exposure time is 10 minutes for 5 ppm. I would recommend you wear goggles in addition to breathing equipment, though.
Presumably that's 5ppm under terrestrial conditions, Venus at 40km has substantially higher pressure, more than is explained by the higher temperature alone, so any given ppm is a greater number of molecules per cm³, right?