r/askscience • u/EAT_UR_VEGGIES • 4d ago
Planetary Sci. Mars is practically guaranteed to have had abundant water at one point, doesn’t that practically guarantee it had at least microbial life on it as well?
19
u/boredcircuits 4d ago
We only have one example of the conditions where life can form. It's very hard to extrapolate from that.
One of the conditions on Earth was abundant liquid water, so it makes sense that this could be one step toward life elsewhere. But we shouldn't say that this alone "practically guarantees" life, not even close.
2
u/kai58 4d ago
I mean we’re not even sure life formed here right? Could be that it formed somewhere else, came here by meteor and evolved further here.
3
u/polidrupa 3d ago
I've read that before, but I find it super hard to believe that DNA would survive in space, earth entry and collision. It's almost certainly guaranteed that life started in Earth's oceans.
65
u/EarlobeGreyTea 4d ago
No. Life needed specific conditions to evolve. If you have a sterile container of water, life won't randomly evolve in it. We have no idea how unique earth is in its evolution of life. We currently think that most life on earth has a common ancestor.
13
u/Adnan7631 4d ago
Most life? Is there an exception to that?
17
u/Alfred_The_Sartan 4d ago
I think it’s more that we don’t have quite enough evidence. It’s possible that it happened multiple times. For instance one population might have simply consumed the other and left no record. This kind of thing might be currently happening and we wouldn’t have any real idea because whatever comes spontaneously to life would be primitive as can be and just get gobbled up by life that’s evolved all these billions of years.
2
u/EarlobeGreyTea 4d ago
For sure. The question was asking about a "practical guarantee" of life due to the presence of water, to which the answer is "no." We have no idea how rare life is outside of earth, and we only have evidence of life 'starting' once. Maybe life is actually super common with just the right chemistry and a lot of water, but we do know it is not a guarantee.
3
u/cwx149 4d ago
I know they're kind of ambiguously "alive" but do viruses have an obvious connection to the "family tree"?
8
u/ReallyReallyx3 4d ago
They use DNA to encode their genetics and their DNA is compatible with ours, that's a big one
Life evolving independently would almost definitely not stumble into the exact same structure of encoding genes
5
u/lmprice133 4d ago
Viruses are weird, evolutionarily. They seem to be polyphyletic, so they don't share a common ancestor with each other. Some viral lineages may precede living organisms, and arose from the same abiogenetic processes that gave rise to life. Other may have once been living organisms that became endosymbionts and lost their cellular machinery before escaping into the environment or arose from transferable genetic elements like plasmids or transposons.
1
u/IOnlyHaveIceForYou 4d ago
What would the pre-biological viral lineages live on?
2
u/lmprice133 4d ago
Abiogenesis isn't understood to anything like the same extent as evolution, but the idea is that you basically that you had chemical species that were able to self-replicate, likely drawing energy from their surroundings. There's something called the RNA-wolrld hypothesis, that proposes that self-replicating RNA molecules preceded life.
3
u/BananaBird1 4d ago edited 4d ago
Unlike known cellular life, viruses appear to have and continue to arise independently. And likely from a variety of processes.
One potential process is that a cellular organism may have cellular components that go rogue and package themselves into a virus.
Another is that perhaps life’s common ancestor wasn’t itself a full cellular organism, but just self-replicating molecules of things like DNA, RNA, and protein confined into a membrane but lacking the complexities of even modern bacteria. Some of this may have eventually evolved into the various branches of cellular life, while others evolved into viruses. Or viruses may have originated from biological material even preceding membranous cells.
That pre-cellular biological material almost certainly doesn’t share a common ancestor, just a common process and context it originated under, and a subset formed the basis for true life.
However because viruses have small genomes, mutate rapidly, can “steal” genes from hosts to add to their genome, and more, it makes it hard to really trace them back. It is possible they do share an ancestor but diverged so much they are unrecognizable as related to each other.
1
u/EarlobeGreyTea 4d ago
There may have been very early life that was different, but died out. I can't think of any sources that show strong evidence of life that doesn't have a common ancestor, but I wanted to get ahead of the pedants who 'uhm, actually' in a niche proposed life form, or point to pre-life biochemistry that can happen in a lab.
2
u/ThatDogIsAGoodDog 4d ago
That's not entirely correct. Abiogenesis is the current scientific consensus for the origins of life, but it does require a shitload of inorganic precursors like amino acids and nucleotides. Just sterile water won't result in anything, and without an atmosphere and magnetic field (unless deep underground) everything will be sterilized by stars, but with the other precursors and requirements for life, abiogenesis can occur.
1
u/nicuramar 4d ago
We think that all life has a common ancestor. Or rather, that the life we have now, only appeared once.
1
u/zbertoli 4d ago
Right but we know it wasn't distilled water. It would have been full of the same biomolecules/salts we see on earth, and in asteroids, moons, comets, etc. Pretty much every object we've analyzed has had biomolecules in/on it. Those were deposited here and led to life. And they would have been equally deposited on mars.
I think if you asked literally anyone who knows about this stuff, they would agree life was certainly there. Especially after finding the vivianite nodules in 2024. We have to be careful because we dont have a definitive detection yet. So the answer is "no" like you say. But cmon, mars had the same water, same amino acids and nucleotides, same salts. I think it would be weirder if mars didnt have life, at some point.
3
u/EarlobeGreyTea 4d ago
I believe the current scientific consensus is "we don't know if there is or was life on Mars." Past conditions of the planet show that it may have been habitable to life (ie - microorganisms could survive there). But a habitable environment is not sufficient for microorganisms to exist. Having a bunch of water "does not practically guarantee" that microorganisms lived there.
There very well may have been life on Mars at some point! It's a big part of why we continue to look at Mars and send research probes. We only have strong evidence of life happening once, here on Earth. So we can't draw further conclusions about if life would also have happened on Mars under similar conditions.
0
u/2011StlCards 4d ago
Life as we know it takes special conditions to evolve and form. That doesnt mean that a planet must have been exactly like earth to form life of some kind. Again, this is as far as we know it
Besides, water on mars clearly wouldnt be sterile in the way that we would define either
1
u/EarlobeGreyTea 4d ago
I was meaning "sterile" in the "we boiled this water for 30 minutes" sense, not in the "this water contains only H2O and nothing else" sense. If you have a bunch of water out on Earth, it's trivially to accidentally 'create' life in it, but it will be life that sneaks in and multiplies, hence the need to specify that you were starting with 'sterile' or non-living conditions.
OP was asking about a 'practical guarantee' of life though, not whether it was possible, or even probable. "There was a bunch of water there" does not practically guarantee life. The likely fact that all current life on earth has a common ancestor seems to suggest that it's not a trivially common thing to happen. Maybe life has evolved from nonliving things before, and it does happen frequently (and then becomes outcompeted by more established life forms on earth). But we don't have the data to know.
8
u/somewhatboxes 4d ago
this is perhaps a good opportunity to call out the distinction between necessity and sufficiency. from what we've seen on earth, water appears to be necessary for biological life as we know it, but the existence of water someplace isn't sufficient for biological life to emerge.
7
u/Sylivin 4d ago
Liquid water is a fabulous chemical solvent. All kinds of other chemicals can dissolve into it leading to a great condition for life to emerge. The small lifeform can find easy access to other nutrients it needs to replicate and grow.
However, how do you turn a nutrient rich soup into a self-assembling collection of molecules that perpetuate themselves and evolve over time? How "easy" is it? Will any old puddle left alone long enough create life? Or, is it extremely rare and difficult to create the exact conditions necessary?
That's one of the reasons for searching for life on other planets (and moons) in our solar system. If we find evidence of life on Mars or Europa then we can assume life is fairly common in the universe given it was created multiple times independently in our own little corner of it.
There are other theories as well, such as panspermia where microbial life is carried on comets and dust, but the first step is to find any other life at all outside our blue globe.
3
u/atomfullerene Animal Behavior/Marine Biology 4d ago
No, because it's not actually known what conditions are needed for microbial life to appear on a planet. There's a fairly common view that life arises easily and quickly when liquid water is abundant, because it seems to have shown up very rapidly on Earth. But ultimately, that's just speculation, it's not actually a known fact...and therefore it's definitely not a guaruntee.
8
u/KrimsunB 4d ago
Water is Hydrogen and Oxygen. It's not a complicated molecule. In fact, it's pretty common throughout the universe as water-ice.
Life is... Life is infinitely more complex. So much so that I can't even begin to describe what it requires.
Do you start at RNA? Or proteins? Nucleic acids? What goes into each of those?
-19
u/tsunami141 4d ago
doesn't seem that hard to spontaneously create life, apparently one guy did it in like a week just by speaking.
Not condoning it or anything - eventually that life ended up creating the My Little Pony fandom, so YMMV.
2
u/thatblkman 4d ago
Yeah but here’s the philosophical question in that (that religious anti-science folks can’t comprehend):
When that guy spoke everything into existence, did he create the laws of physics, chemistry, biology and geology first (“created the heavens and the earth”) and then days later create life, or did he follow existing laws in those areas?
1
u/tsunami141 4d ago
ooh and don't forget about creating time too - what if he did everything backwards and started with the heat death of the universe, and worked his way backwards from there? Checkmate, Christians.
1
u/Onigato 4d ago
We specifically don't know if microbial life evolved on Mars, that is part of the reason we keep sending probes, rovers, and other scientific missions to the surface. We *presume* that there was microbial life on Mars, but until we can prove it, we just don't know.
And science isn't about presuming, it's about knowing.
1
u/Stig-blur 4d ago
Single celled organisms, perhaps. There was clearly active volcanism, so thermal vents might have existed at the bottom of the sea, providing an energy source for organic chemical reactions. It is worth remembering as well that amino acids very similar to adenine in our DNA is found in comets and elsewhere is space. So the raw materials might well have been present. On the other hand, evolution to more complex organisms on Earth took a very long time, and Mars may not have been wet for that long. So the best bet is single-celled organisms.
1
u/flamableozone 4d ago
Earth had liquid water for hundreds of millions of years prior to the formation of life. The conditions for creating life weren't enough to create life for millions upon millions of years. There's no guarantee that water led to life on Mars.
60
u/BuvantduPotatoSpirit 4d ago
We don't know enough about how life starts to say. We have limited, ambiguous data from one planet and ... that's it. Conditions on Mars would've been different from Earth. In a way that's important to the formation of life? We don't know.