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.