3.77-Billion-Year-Old Fossils Found, Could be Earliest Evidence of Life On Earth (theguardian.com)

An anonymous reader shares The Guadian report: Scientists say they have found the world's oldest fossils, thought to have formed between 3.77bn and 4.28bn years ago. Comprised of tiny tubes and filaments made of an iron oxide known as haematite, the microfossils are believed to be the remains of bacteria that once thrived underwater around hydrothermal vents, relying on chemical reactions involving iron for their energy. If correct, these fossils offer the oldest direct evidence for life on the planet. And that, the study's authors say, offers insights into the origins of life on Earth. "If these rocks do indeed turn out to be 4.28 [bn years old] then we are talking about the origins of life developing very soon after the oceans formed 4.4bn years ago," said Matthew Dodd, the first author of the research from University College, London. With iron-oxidising bacteria present even today, the findings, if correct, also highlight the success of such organisms. "They have been around for 3.8bn years at least," said the lead author Dominic Papineau, also from UCL.

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[beelsebob]

With life being at least 83% as old as the planet according to this result, it makes me begin to wonder "has life been on earth ever since it formed?"

That's clearly not a question we're going to answer today, but it might have drastic impacts on the drake equation if there was some requirement for life that has to happen as the planet forms.

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[MightyMartian]

I'm not a huge fan of panspermia in general, as it seems to add an additional step to a problem, but really just pushes the question back. I can concede that it is possible that Mars, which may have been more conducive to life earlier, may have been the source of life on Earth, but until we find some evidence that life actually existed on Mars at some point, and further can show enough molecular commonality with life on Earth, I think Occam's razor suggests we have to stick for the moment with life being indigenous to Earth. That being said, even if we found life on Mars that appeared to be part of the same twin-nested hierarchy as life on Earth (in other words, we're all on the same family tree), that still wouldn't really answer the question, since it's easily conceivable that the transit could have been the other way; Earth to Mars.

What we do know right now is that some of the most ancient genes suggest these early organisms at the root of the tree of life were autotrophic and probably hung around deep sea vents in waters rich in iron and sulfates (this is the idea behind the iron-sulfur world hypothesis). While this doesn't necessarily discount Mars either, as Mars in this early era had oceans and was very likely geologically active, it still suggests to my mind that Earth is still a pretty clear contender for the source of the life we see today.

A lot will depend on whether we can find other life in the solar system. If we go to Mars or Europa and end up finding organisms that have a clear molecular relationship to life on Earth, it certainly proves the limited form of panspermia happened, whereas if it turns out there is no evident genetic relationship, then that ought to tell us life is pretty damned common in the universe, and even in conditions like the Hadean Epoch, when Earth was quite literally at points a hell, life can not only evolve but possibly even flourish.

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[MightyMartian]

That describes parts of the Hadean Epoch, and in particular the early parts, but there is some evidence that even during the Hadean Epoch there was liquid water, possibly even oceans. From https://en.wikipedia.org/wiki/..., it states that even though surface temperatures were much higher, the much higher atmospheric pressure meant that liquid water could exist. Considering some evidence that the earliest organisms were autotrophic and lived in an environment very much like existing deep sea vents, one can surmise that while this environment would be pretty damned hostile, it would still have had the critical ingredients; water, complex organic chemistry and an abundance of energy.

Similar to what was found on Mars?

[mykepredko]

When I RTFA and saw the reference to hematite, I wondered if this is similar to possible evidence of life found on Mars: http://mars.nasa.gov/mer/scien...

Any biologists out there care to explain if this is similar or different?

If this is similar, does this provide a clue as to how life starts to evolve on a planet?

Re:Earliest evidence of life on Earth?

[MightyMartian]

I remember reading an observation by a chemist or molecular biologist years ago that abiogenesis events might go on all the time, but the problem for any new protolife is that if it appears in an already active biosphere where a fair portion of the existing organisms are very very good at gobbling stray bits of organic material, it's not going to last long at all.