| Life Possible
under Extreme Conditions |
Lake
Vostok and Europa compared
In 1996, Lake
Vostok was discovered. Discovered? A lake discovered in a
time when it seems like every single inch of the globe has been well
documented and put on a map? Yes. But Lake Vostok is special: it is
overlaid by about 3,710 meters (12,169 ft) of ice and may be 500,000 to
1 million years old. The water is in a liquid state: how this is
possible, no one really knows.
It is far from
unique: on the South Pole alone there are some 70 places
where ice has covered water in history. But Lake Vostok is a big one:
48 by 224 kilometers (30 by 140 miles). Scientists are however very
hesitant to drill to the depth of the lake and take a sample of its
liquid water.
Through computer
simulations of the water flow they realized that it
might be very well possible that huge quantities of gases like oxygen
and perhaps carbon dioxide are dissolved in the water.
Next to the
obvious danger of contamination of the water by bacteria in
present day Earth’s atmosphere, which would render research useless,
there is the very real danger of the water being under tremendous
pressure and bursting out from underneath the ice, if that cap is
breached.
[This view of Lake
Vostok was taken
by the Radarsat satellite. Scientists are debating how to best conduct
exploratory drilling into the lake to prevent contamination. They say
that if the lake is just drilled into, it could pop like a shaken soda
from millions of years of built-up pressure.]
So, what’s the
interest in the lake then?
Well, the lake
has a striking likeness to one of the Jupiter moons,
Europa. Europa is also covered with a thick layer of ice, but has a
liquid ocean underneath. And the same problems are faced: Europa’s
ocean also could be under pressure like a can of soda, and it is also
under a very thick layer of ice. But - more importantly - it could
harbor life. So we have the possibility to do research on Europa-like
conditions on our own doorstep: that is what really makes Vostok
interesting…
As mentioned
earlier, nobody’s really sure why Vostok’s water is in a
liquid state. We do however know why the water beneath Europa’s caps is
in a liquid state: gravitation. The gravitational pull of Jupiter on
Europa is enormous. This causes the shape of Europa to be stretched and
squashed like a large soapbubble. This constant change in shape causes
friction and this friction heats up the moon from the inside out,
causing the liquid interior. Now most scientists agree on one of the
basic conditions to make any form of life possible: liquid water.
Lake Vostok is
deep under the Antarctic ice and not one light particle
did ever reach its waters. The same is true about the ocean beneath the
icy crust of Europe. Is light a necessity for any form of life to
exist? Scientists no longer believe this to be true. In the depths of
the Atlantic and Pacific Oceans there is life. And not a little bit of
it too: marine biologists Thomas Gold and John Barross think the
biomass below the surface of the oceans may be much larger than that on
land.
It is quite
possible that new forms of life still “leak” from sea to
land. Barross: “Who knows, the subsurface biosphere may be inoculating'
the surface biosphere with new seeds of life. And perhaps, if there's a
biosphere beneath the surface here, there might also be one under the
surfaces of other planets.”
Special interest
is given to the so-called superthermal extremophiles,
microbes that can survive many tons of pressure and temperatures up to
130 degrees centigrade. The chemical composition and heat of the water
above the “smokers”, volcanic vents on the bottom of the deepest parts
in the ocean, would normally prohibit any form of life, but the
extremophiles thrive in this acid hell.
After the
discovery of these record holding survivors, we have been
forced to move the barriers around the environment where we deem life
possible a great distance. We now know that life is possible at extreme
heat and pressure, and that is exactly the sort of environment we hope
to in the depths of both Lake Vostok and the ocean of Europa.
Many scientists
are practically drooling at the idea of investigating
the sub-surface waters of Europa. No other body in the Solar system is
a better candidate for harboring life than this Jovan Moon. Its size is
practically equal to that of our own moon.
Imagery from the
Hubble Space Telescope (HST) proved that is has a thin
atmosphere containing oxygen, although just enough to fill about three
stadiums. These facts, combined with the high probability of liquid
water make Europa a desired object of research; so much desired even
that the planned Pluto trip was deferred in favor of a drilling
expedition to Europa.
While the
similarities between Vostok and Europa are obvious, the main
difference is this: we can go back to Vostok over and over again. On
Europa we only get one chance to get it right…
Hans de Vries
(dutchie) for Armageddon Online
November 2004
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