Question
What did they use to find out whether or not there used to be water on Mars?
Answer
Hi!
My name is Dr. Sten Odenwald, an astronomer at NASA and the author of the question-and-answer book 'Back to the Astronomy Cafe' and the Astronomy Cafe website.
There have been many lines of evidence pointing this way. First, there is water ice in the south polar cap of mars so we know this substance exists on mars. Second, there are many land forms that could only have been sculpted by running water, not winds. Geologists can tell the difference between liquid erosion and aeolian erosion, so thats n ot a real consideration. From impact craters that straddle many of these running-water formations, we can date the time of their formation to as recently as a few hundred million years ago.
The two mars rovers which have been exploring the surface for over 14 months have discovered an iron ore called hematite which only forms under the action of liquid water, and in fact the mineral deposits and pearl-like condensations seen by Opportunity show that the region it has been exploring has been recently under water in some large pond-like basin. For more on this 'clinching' discovery announced last spring, visit the mars rover site at JPL and read their press release.http://www.space.com/scienceastronomy/solarsystem/mars_water_000620.html
We think that any liquid water, and life, that exists on mars today is located below surface in aquifers that we suspect exist.
http://www.space.com/scienceastronomy/solarsystem/mars_water_000620.html
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