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

On Monday we described the existence of subglacial lakes in Antarctica (and elsewhere in the solar system), and the effort to bore into them to sample their water and surfaces.  Geochemists and geologists have various questions they'd like to answer about this interesting phenomenon.  Such ice sheets initially form on the surface just as it does in the winter where you and we live, but in an ever-winter climate it never thaws.  As it becomes ever thicker, the insulation it provides from solar heating, the pressure at its base, and geothermal heating from below melt water at the earth-glacier interface--it liquifies the ice there.  The water then builds up over time in to a sizable lake, and will naturally also follow available ground channels to connect with other such lakes and so on.  Maybe even to connect to subsurface water.

On Earth, there is an old saw that where there's water, there's life, so one question is whether that is a rigorous enough theory to suggest that there's life in these subglacial Antarctic lakes.  And since there is similar subglacial liquid water elsewhere even in our own solar system, such as on Jupiter's moon Europa, the question is naturally raised as to whether there's life there, too.  Or all over the universe.

Do Earthly matters matter?
What would we expect to find in water samples brought up from probes into Antarctic subglacial lakes?  Well, we know that millions of years ago, there were complete living ecosystems, even tropical in their abundant and diverse life.  So, if they could last long enough, remnants must have once been on the surface when it initially froze over and could still be there today.  That would range from what would now be fossils, to perhaps the kind of frozen, mineralized microbial life that has been found at the surface of Antarctica.  So it would be no total surprise to find that kind of evidence (though this project is not going to bore into the ground surface below the lake, where fossils of multicellular organisms might be most likely to be found).  We have to leave such speculations to geologists and paleontologists.

One could also not be surprised if there are organic molecules in the water that were once part of that ancient life, and were embedded in the initial ice layer as it formed.  Conditions may have been stable enough that such molecules didn't degrade.  DNA is unlikely to have been preserved intact, but many kinds of molecules and perhaps even nucleotides (DNA building blocks) might have survived the Long Chill.  Finding them would be at most mildly interesting (since we know they must have been there at one time).  Organic molecules continually rain down on Earth from space, so they would have landed on the forming ice, and hence be in the melted subglacial water.

Since we know that fish and many other types of life have adapted genetically to be able to live in the frigid waters around the poles, could we find them in these subglacial lakes?  It seems unlikely, to us at least, for several reasons.  First, terrestrial life would have had to survive the long eons of climate cooling and then unmelting snow, eventually covering the entire surface leaving nothing to eat, and then somehow adapted to live embedded in ice for millions of years until the Big Thaw at the bottom.  So this seems highly unlikely and we doubt the lakes' explorers expect that kind of life.

Darwinian adaptation can be remarkable, but it seems to be a stretch in this case, unless signs of life that were found were from things that seeped up from underground or from the surrounding oceans. 

Perhaps micro-organisms could have adapted to the cold, but where would they have lived during the millions of years that the earth-glacier interface was frozen solid?  It would probably have had to be under the surface, surviving and adapting somehow until a liquid lake formed--perhaps they lived in underground liquid water and then seeped into the subglacial lake as it formed?

Most likely one would find simply signs of life--molecules of life, but that would in itself tell us nothing since it would be expected for the above reasons (that there was life there before the freeze).  In a way, perhaps we would be surprised not to find such molecules, though in this case the planned samples will be small--only a few hundred ml of liquid--so a very chancy sampling of the lake.

So, one wonders just what the evidence for life would be that would be any sort of surprise.  Even if it's true that on earth where there's water there's life, it doesn't mean that the 'life' is alive.  It would take some clever argument to suggest how adaptations would have been possible unless as we suggested above it were from subterranean water and/or perhaps had some deep channels to the water surrounding Antarctica.

In any case, it will be interesting to see what is found.  It may tell us things about geological history and processes.  And maybe we, not geologists, are missing some points of the goals of the expedition that didn't come through in an interview program on the BBC or on the Wiki pages devoted to subglacial lakes.

Life in space
But what about the sexy hint that it will tell us about life on ice-bound orbs like Europa?  Just because, or if, it's true that where there's water there's life on earth, has no bearing whatever on the relevance of this kind of generalization elsewhere.  Water is compatible with life, at least life as we know it here, and life evolved from watery beginnings and hence depends on water, but water doesn't cause life.  What's in the liquid water under Europa's icy coat may be interesting for all sorts of reasons, but to justify it on the grounds of it being evidence for life, and using Earth as a precedent, is the kind of stretch that can be very misleading.

The public is hungry for science stories (and for science fiction), and NASA does big business in 'astrobiology', at least partly if not mainly as a marketing component.  And if half our population doesn't believe that evolution took place, how can we expect them to be able to discriminate the fairy tales used to justify the cost of space exploration?  Maybe it would be better to be a bit more critical in what is said to scientists and public alike, about the value and interest in simply learning more about the universe--genuine excitement about the genuinely interesting knowledge of existence that can be gained.  Or, equally, whether that value is worth the cost given other problems that people face here on the surface, where it's warm and indisputably lively.

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.