Martian gullies turn tide in hunt for life
PLANETARY SCIENTISTS are eager to step up their search for life on Mars after news that liquid water seems to have flowed down gullies in the planet's mid-latitudes within the past few years. Mike Malin of Malin Space Science Systems in San Diego, Calif., and his team saw gullies forming on two crater walls on Mars between 1999 and 2005.
The light colour of the gullies and their characteristic shape has convinced Malin that they were carved by flowing water.
Malin is not suggesting that there are lush lakes, or waterfalls flowing down the red planet's cratered surfaces. More likely are brief spurts of rapidly evaporating water that push a mudflow down a slope. Malin's peers are taking the news seriously.
In 2005, Heldmann, a geomorphologist at NASA's Ames Research Center in Moffett Field suggested that gullies on Mars could be caused by water flowing under current martian conditions.
Since Malin announced his results, HiRISE, the High-Resolution Space Imaging Experiment that is on board the Mars Reconnaissance Orbiter (MRO), will also be following up Malin's results.
Images of gullies
Alfred McEwen, principal investigator for HiRISE, says that the instrument will take images of the gullies identified in Malin's paper several times over the next few years.
But HiRISE might be able to shed more light on exactly how the gullies are formed. McEwen accepts water flow as a reasonable hypothesis, but argues that other mechanisms, such as dust deposits, can't be ruled out.
Pin-point expertise
But the only way to find out for sure is to land on Mars and go to the gullies. Landing on or near the bumpy craters, however, would require pinpoint expertise.
Matt Golombeck, landing-site scientist of the Mars exploration program, says that none of the landers being considered at the moment has that capability.
No change
The European Space Agency is also unlikely to change its immediate plans. Its next Mars mission called ExoMars and headed by Jorge Vago, is scheduled to launch in 2013.
It aims to land in a flat area and drill into the rock to look for organic matter, among other things. Attempting to land near the gullies would escalate costs enormously. But NASA has recently called for proposals for a scout mission to Mars.
Malin has proposed a rover to land on plains near the crater, then drive down into the gullies.
Hugely significant
Either way, the finding that groundwater is seeping out of Mars is hugely significant for those who hope one day to find life on the planet. Liquid water is essential for life at least for anything like life on Earth.
And if life does exist on Mars, the only place it is likely to be able to survive is underground, and that is out of reach of our probes.
KATHERINE SANDERSON
Nature News Service
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