Microbes Likely Abundant Hundreds of Meters Below Sea Floor

sciencehabit writes "Samples drilled from 3.5-million-year-old seafloor rocks have yielded the strongest evidence yet that a variety of microorganisms live deeply buried within the ocean's crust. These microbes make their living by consuming methane and sulfate compounds dissolved in the mineral-rich waters flowing through the immense networks of fractures in the crust. The new find confirms that the ancient lavas formed at midocean ridges and found throughout deep ocean basins are by volume the largest ecosystem on Earth, scientists say."

Comments

Re:First life form

[Immerman]

Not even close. They may possess some similarities to the first cellular life forms which were almost certainly also chemovores (though likely lived in amino-acid rich muck on the bottom of shallow seas), but these organisms have been evolving for four billion years since then - they are every bit as evolved as humans, arguably far more so since their generations are so much shorter. They simply spent more time optimizing for a particular ecosystem niche whereas our ancestors kept changing directions dramatically. I mean come on - living in giant clonal colonies of billions of specialized individuals? Clearly a fad. It'll last a few billion years more, tops.

Hazen

[CuteSteveJobs]

This isn't new: Recommend Professor Robert Hazen's book on the origins of life. He says no matter where you go on earth, deep into sea sediments or the rock of deep undergrounds mines, every cubic inch of the Earth is teaming with microbes. Worth noting the vast majority of them are indifferent to you. Even out of the ones that made their home on your body (for every cell on your body there are 10 bacteria along for the ride), the vast majority of those are indifferent or even beneficial. Only a tiny percentage are pathogenic, and often only when your immune defences are down. On the origins of life it isn't that it is hard to come up with an explanation, but instead there are so many plausible theories they don't know which one it might have been. It may be far easier for life to get started than we like to think. http://www.smithsonianmag.com/science-nature/The-Origins-of-Life.html

Re:Hazen

[Anonymous Coward]

He says no matter where you go on earth, deep into sea sediments or the rock of deep undergrounds mines, every cubic inch of the Earth is teaming with microbes.

What about in the outer core? How do the microbes survive in liquid iron?

Oh, you just meant in the crust, right? So finding life hundreds of meters below the surface in the crust might actually be a surprise? 6371 km deep, there is no life. 0 km deep there is a lot of life. The question is how deep life can survive (between 0 and 6371 km). Now we know it can survive hundreds of meters below the surface in cracked rocks. Can it survive deeper than this? It certainly can't survive down to the core, so there must be some interface boundary where even the most extreme of extremophiles won't survive. That is the point, and that is why this finding is new.

Re:Europa

[Immerman]

Indeed. In fact sunlight was probably largely irrelevant to Earth life for most of the first billion or so years it existed. Prevailing opinion is now that chemical energy from hydrothermal vents was probably the primary "food" early on, then eventually perhaps each other. Which makes sense if you think about it - complex chemistry would probably find chemical energy far more accessible than capturing radiation. Photosynthesis doesn't appear to have really caught on until much later, with the evolution of chlorophyll likely causing the first mass extinction event as it flooded the seas and atmosphere with toxic oxygen.

Of course Europa is a much smaller petri dish than Earth, and less energetic, so I'd suspect life would evolve much more slowly. If we do find life there, and it's anything like us (DNA, etc), it might provide a fascinating glimpse into what primitive life on Earth may have be like. Everything here on Earth is the product of around 4 billion years of evolution.