Note About The Deep Biosphere Miles Deep In The Earth's Crust

 a short review of life deep in the rock below the surface of the earth.  

So far as deep as we look into solid bedrock (3miles so far) we find living microbes!  They live off of the very chemistry of the rock itself, no sunlight needed.

for instance, Desulforudis audaxviator (audaxviator means Bold Traveler, from a phrase in Jules Verne's Journey to the Center of The Earth) feeds off of radioactive decay!  Slow radioactive decay of Uranium or Potassium is enough to produce molecular Hydrogen, H2 from water which seeps down there, which the bugs can combine with CO2 dissolved in the water, to create the energy and organic compounds they need to live.  They are found around the world miles deep in mines.

This discovery of a deep biosphere is only a few decades old.  We have much still to learn.

One exciting aspect of exploring these depths is that we might be able to find truly alternative forms of life.  that is... All life we know of on earth today is biochemically almost identical.  The core biochemistry (building and breaking down sugars, using DNA, RNA and proteins etc.. ) all works the same, plants animals fungi bacteria...   

This is odd, was life only able to happen in THIS ONE WAY on earth?  or are there other ways it can develop from chemistry  (this leads to profound scientific, philosophical and theological questions)?  

Are there alternative forms of life lurking down there?  so far we don't know.  But here is the thing:  

Another recent discovery only a few decades old is that we are TERRIBLY BAD  at detecting live microbes everywhere we sample.  We know this because we can detect a wide species diversity of Genomes from the DNA we can sample from all kinds of environments even tho we don't know how to physically or visually detect the microbes  themselves that make that DNA.  and we certainly we don't know how to grow them in the lab to study.

This leads one to speculate that if there are alternative forms of life down there that don't use DNA, we have no way to detect it yet!  And since we keep finding all kinds of new regular life forms that can live in bizarre conditions using bizarre forms of chemistry to fuel themselves... It is possible.  

Also growth is VERY SLOW in the deep biosphere and so it is possible that the ubiquitous kind of life that we know about hasn't been able to outgrow the alternative forms, which is presumably what has happened at the raucus and fast growing competitive surface of the earth (if alternatives existed way in the past).

Such fun

Micheal Gross
Life Underground

(free access for may, jun2021)
https://www.sciencedirect.com/science/article/pii/S0960982221005947