Is there water on Mars?  We know the answer is “yes”, since Mars has ice caps at both poles that grow and shrink with the seasons.  The real, harder questions are:  how much water is on Mars, and where is it located?

On Earth, of course, a lot of the water is in liquid form on the surface, with a significant amount in ice, also near the poles.  Water vapor also is a small but important component of the atmosphere.  Mars, on the other hand, has no persistant liquid surface water, and its atmosphere is drier than the driest desert on Earth.  However, features on the Martian surface strongly suggest that Mars used to be wetter in the past:  various telescopes and probes have found terrain that looks like seashores, river valleys, and other hallmarks of water erosion.

Enter the Phoenix robotic lander.  The probe’s mission is to dig underneath the surface to analyze the soil, looking specifically for subsurface water and anything else interesting.  Almost immediately, Phoenix’s scoop uncovered ice, which can be observed to melt over a period of four Martian days:

This finding is important for several reasons.  First of all, if there was surface water on Mars in the past, where did it all go, and how long did it take to change Mars from a wet planet to a dry one?  Secondly, all life on Earth contains water as an essential part of its chemical make-up, so subsurface water may be the best place to look for life on Mars.

Detecting life isn’t as simple as it might seem at first, not least because the environment on Mars is substantially different than on Earth, so Martian life might not resemble Earth life.  As Phoenix does its complete chemical analysis of soil samples, we will learn a lot, whether life is found or not, so keep an eye on the news.

Posted by Matthew R. Francis under Science Ideas & Science News |