In 1672, while observing Mars through his telescope, the Dutch astronomer, Christian Huygens, noticed a white spot, probably one of the planet’s polar caps. Some 15 years later, he would write a book discussing what was required for a planet to support life and speculating about the possibility of extra-terrestrials.
We now know that the poles of the Red Planet contain hidden reservoirs of ice that lie possibly only inches below its black and forbidding surface. Evidence about sub-surface ice emerged during 2002, but fresh data collected by the two NASA orbiters (Surveyor and Odyssey) now point towards huge ice deposits in the northern polar region, an expanse considerably larger than that around the planet’s South Pole.
The presence of vast quantities of hydrogen detected by the suite of instruments on board the orbiters clearly suggests the existence of water. The gullies and channels that mark the dusty, red landscape had convinced astronomers that water once flowed on the planet.
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The question was: where did it go? The new data suggest that the water drained towards the poles until it was trapped as ice beneath a protective layer of soil.
The significance of these findings cannot be exaggerated. Ice deposits on Mars lend some evidence to the hypothesis that the planet was once both wet and warm – the two basic conditions for supporting life. As scientists acknowledge, there can be no ruling out that some form of life, probably only in some primitive microbial form, survives even today.
In 1996, the arresting possibility that there was life beyond Earth seemed as if it had been confirmed after NASA scientists claimed the existence of fossil bacteria in a meteorite that originated from the planet.
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However, doubts that the structures on the rock were caused by chemical processes or by terrestrial contamination persisted which have led to a general consensus that the fossil find was inconclusive.
Nevertheless, we now know that microbial life can survive in places once regarded as totally inhospitable – for example, in a thermal spring or within a bed of ice in either of the Earth’s poles.
By implication, such knowledge has increased the belief in the possibility that there may have been, and may even be, life on Mars. One result of this, of course, has been a virtual rush for the Red Planet.