Life On Mars
BBC2 9.00pm Thursday 11th January 2001
If there's life on Mars, it would be
one of the most important discoveries of all time. It would mean
life on Earth was not some special unique event - it would mean
there's likely to be life throughout the Universe.
In the first of two special programmes on Mars, Horizon explores
how the search for Martians is now hotting up, and why many scientists
are becoming more and more convinced that life may have arisen on
Mars, and that there may even be something living there now.
Today, Mars is a frozen desert - the average temperature is -70ºC.
But long ago Mars was very different. The first clues came from
Mariner 9, which sent back fuzzy images of the surface of Mars,
revealing volcanoes, canyons and meandering valleys that looked
like ancient rivers. Rivers form from rain water run-off, rain comes
from clouds, and clouds mean an atmosphere. If there had been rivers
on Mars, it meant the planet had once been warm and wet, like the
Earth - the perfect conditions for life to evolve. For thirty years
scientists like Mike Carr have been poring over more and more detailed
images of Mars, trying to piece together the planet's history. When
the latest probe, Mars Global Surveyor, was launched three years
ago, everyone hoped its high resolution electronic cameras would
settle the debate about the ancient rivers. Thousands of close up
images were beamed back, revealing sections of the valleys in fantastic
detail, but none of them were any use. Over the billions of years,
the valleys had all been eroded and filled with sand. It was impossible
to say how they had been formed. Then finally, the Mars Global Surveyor
team noticed a tiny feature in one image, which convinced them that
billions of years ago there were rivers and lakes on Mars.
But did these warm, wet conditions last long enough for life to
evolve? An unusual lake in Turkey has convinced Scottish geologist,
Mike Russell, that Martian lakes were once teeming with primitive
bacteria. So if life did evolve, is it possible that something is
still living on Mars now? It would have to survive millions of years
deep frozen in the Martian permafrost.
Russian biologist David Gilichinsky has been studying how long microscopic
life on Earth can survive frozen in permafrost. Each summer he travels
to Siberia to drill into the permafrost. So far he has managed to
resuscitate bacteria and algae which have been frozen for three
million years at temperatures below -10ºC. His latest results
from Antarctica suggest bacteria may be able to survive even longer
at even colder temperatures - perhaps thirty million years, at -20ºC.
Somehow bacteria live off the tiny amounts of liquid water that
exist even in permafrost this cold. So perhaps they could still
be clinging on, below the surface of Mars.
Astronomer Bill Hartmann, believes that there may be far more going
on beneath the surface of Mars than anyone suspected. Last year,
Global Surveyor sent back astonishing images of gullies running
down steep slopes on Mars. Bill is convinced these were carved by
water erupting from underground aquifers, heated by volcanic activity
deep below. If he's right, then perhaps there has been life on Mars
for billions of years, surviving undergound when the surface of
the planet became the freeze dried desert it is now.
The search for life on Mars is moving underground. Over the next
few years a series of missions to the Red Planet are planned, but
any signs of life will be hidden away - buried deep, and hard to
find. When will Mars give up its greatest secret?