Monday, September 10, 2012

Life in the cold zone? And in space?? Part I

This post was triggered by a BBC Radio program called "The Life Scientific" in which a geologist, Martin Siegert, was interviewed about the team effort he is leading to obtain samples of water from Lake Ellsworth, to see if there's any life there.  After all, on Earth, where there's water, there's life.

So what?  So what, is that this is a subglacial lake, several km below the Antarctic ice sheet.  The liquid water in this lake hasn't seen the light of day for millions of years.  In fact, aerial radar exploration has identified hundreds of lakes at various depths below the continent's icy surface.  One of, if not the, largest is Lake Vostok of which this is an image:

As the ice forms over the surface and grows in thickness, the pressure at its base, combined with thermal heating, causes the base to melt (not to be warm by our standards, but to be liquid).  The lakes can be very large.  Ellsworth is 4km deep, 10km long and tens of meters in depth.  This makes it manageable to explore: very isolated from surface life, yet accessible and samples can be drawn from the top, the water, and the lake bottom.  By contrast, Vostok is largest, 250x50km and 350m deep.  This lake, too, is being explored.

Exploration is a challenge since one needs to preserve the lake ecology and not contaminate it with the probe that is bored into the lake.  What the explorers want are pure (uncontaminated) samples of the water, ice, and bottom surface of the lakes, to define its characteristics.  Once contaminants are introduced, this will be very difficult, so international standards for cleanliness are used to help prevent this and save the subglacial environment for future exploration.

The Siegert-led team is being very careful.  The method wasn't described in detail in the interview, but the idea is that a narrow sterile probe will slowly melt its way down, staying surrounded by liquid water.  Once there, after several days of boring-down, it will have 24 hours to collect a number of small samples from various depths and so on, and then will be withdrawn.  At that point, the bore-hole, which was always water-filled, will freeze over, re-sealing the lake and preventing contamination from the surface.

So what?  Isn't water just water?
There are many interesting questions a geologist can ask about such an unusual (for us) phenomenon as a liquid water lake deep below thick, very cold glaciers.  But one that, as usual, is raised to justify the costly explorations using special boring technology to keep things clean, is based on the current understanding that here on earth, wherever there's water, there's life.  Or so the 'theory' goes.  But is it correct?  What would one expect?

Because of continental drift and other factors in Earth history, Antarctica used to teem with plant and animal, and surely also microbial life.  Fossils have been found, and they show that the climate was once warm if not tropical, when the land mass was not located at the frosty pole.  But gradually, the movement of the continent to its down-under location caused its climate to cool, and eventually to stay below freezing temperatures all year round.  Gradually, the glacial covering built up, as precipitation and condensation froze and was not thawed.

This means that there was life there once and for a long time and it was diverse.  So either it all just froze into extinction, or adapted.  We know of 'antifreeze' genes that allow organisms to life at below-freezing temperatures, so one possibility is that life adapted to this new temperature by natural selection for survivable physiology and form.

There are other issues as well.  It is known from direct exploration that other objects in the solar system, like Jupiter's moon Europa, are covered with ice and have liquid water underneath.  And, of course, the hype-machine is very actively promoting the excitement of the apparent fact that Mars was once at least partly covered in water.  Why we haven't seen the Little Green Men (or even little green algae) is the question you're paying taxes handsomely to answer!

So, does this rather generic reasoning mean we would expect to find life in these lakes?  And what kind of 'life'?  And what does this tell us about life elsewhere in the universe--if anything--and why would such a question ever arise if it is more than just hype seeking attention and funding?  Is this just some geologists' boondoggle to poke around in a lake because it's there, or is there a real scientific question here (about life, not about geology)?

We'll address these questions tomorrow.

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