Water on Mars--now!

Okay, now this is just magnificent if it does indeed prove to be true. New Scientist is reporting that the now-defunct Mars Global Surveyor has taken photos that indicate flowing water on Mars within just the past several years:

Liquid water has flowed on the surface of Mars within the past five years, suggest images by the now lost Mars Global Surveyor (MGS). The results appear to boost the chances that Mars could harbour life.

In 1999, MGS spotted gullies carved on the sides of Martian slopes. Thousands of gullies have been imaged since then, most recently by the Mars Reconnaissance Orbiter (MRO).

Many scientists believe the gullies were carved by liquid water, although others have argued they are due to avalanches of carbon dioxide gas or rivers of dust.

The gullies appear to have formed sometime in the past several hundred thousand years, since impact craters have not accumulated on top of them. But exactly how long ago material flowed through them has not been clear.

Now, new flows have appeared in two of the gullies monitored by MGS, showing that they have been active within the past several years. The research was led by Michael Malin of Malin Space Science Systems in San Diego, California, US. That company operates the Mars Orbiter Camera on MGS, which acquired the images.

There's been excitement about water on Mars before. Research has shown that despite Mars' low atmospheric pressure, liquid water can exist on the planet's surface for modest lengths of time under certain circumstances, although this of course hasn't been directly observed. And over the years there have been rampant online rumors among planetary sciences email lists that seeps or standing water had been discovered (nothing quite so dramatic I'm afraid--the ensuing press conferences discussed "fresh" runoff channels and the sapping of crater walls, indirect evidence of water's presence, but not inconclusive).

The trouble with announcements of this sort is that so many people, like Fox Mulder want to believe that it's easy to jump to conclusions. There may indeed be alternate explanations for this, even if we desperately want it to be water-caused. Either way, this is a fascinating discovery.

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