This BBC item reports the discovery of microtubular structures in rocks in Canada dating from 3.8-4.2bn yrs ago, which were originally beneath the ocean at hydrothermal vents. http://www.bbc.co.uk/news/science-environment-39117523 It seems the findings are not yet fully accepted, but if they are of biological origin, that would push the earliest evidence back from stromatolites in Australia dated at 3.7bn yrs ago. Since the Earth is 4.5bn yrs old, it starts to look as if life arose pretty soon after its formation, suggesting either that it arises fairly easily, given the right conditions, or -more controversially - that some form of panspermia mechanism might conceivably be at work. Anyway, interesting, I thought.
Speaking of ballistic panspermia, whatever became of that meteorite that was determined to have originated from Mars and showed fossil "signs" of life? I think it was back during the Clinton administration.
My recollection is that eventually there was an inorganic explanation for what was found - but it was a long time ago and my memory may not be accurate.
Yes you are quite right. I looked this up and found a Smithsonian article about it, here: http://www.smithsonianmag.com/science-nature/life-on-mars-78138144/ I imagine a similar critical process will now take place, concerning these early supposed fossils from Canada. We'll have to wait while the debate rages.
I believe that there might be indirect evidence from Australia that points to an earlier date consistent with the new Canadian findings. The Australian evidence concerns organic inclusions in zircons. http://www.sciencemag.org/news/2015/10/scientists-may-have-found-earliest-evidence-life-earth I can imagine four possibilities off the top of my head: 1. Life arises very easily. I think that this one is exceedingly unlikely, based on the incredible complexity of even prokaryotic cells. You don't just throw metal, plastic and silicon into a container, shake it up, and get a cell phone. There was some other unknown process at work in the very early days that resulted in the first cells, and I expect that process would have required a significant amount of time. (It might also be expected to have left traces, such as a class of non-living chemical replicators that we don't see here on Earth.) 2. Whatever is responsible for these early traces might have been "life", but not life as we know it. It might have been some now-extinct proto-life that didn't possess all the current complexity in chemical metabolism, genetic code, protein synthesis and so on. It might have been something a lot simpler than what we are used to when we look at bacteria and archaea, something exceedingly basic such as the hypothetical chemical replicators I mentioned in 1. I think that this possibility is far more likely than the first. 3. Or life might not have originated on earth at all. It might have originated elsewhere earlier in the universe's history and was seeded here by some as yet unknown process. I kind of like this one, but the mechanism of life-dispersal is a big hurdle. 4. Lastly, the dating of these traces may be way off or they might not be traces of life at all. They might have inorganic origins. Personally I think that this might be the most likely of these four alternatives.
Yes, very reasonable. I think I'd be inclined to trust the dating of the rocks, as that seems a fairly well established technique. It must be open to question whether these findings are really unambiguously evidence of life, though. It initially struck me as perhaps significant that the dates from Canada and Australia sort of corroborate each other, at 3.8bn yrs or a bit more. But I suppose that could be selection bias, in that it would be rocks from around that age where people would be thinking it would be exciting to try to find life. So they look for it and, er, find it, ...or maybe not.
I believe it was from the deep ocean and because of decreased gravity, grew bigger. Like the Teenage Mutant Ninja Turtles.
