One of the great mysteries about Mars is when liquid water last flowed across its surface. There's little doubt that in the distant past, water formed lakes and rivers, and perhaps even an ocean. But that was billions of years ago, when the planet was young. The question now is whether water has flowed more recently.
A study published earlier this year says the answer is yes -- there's evidence of flowing water as little as two million years ago.
Matthew Balme of the Planetary Science Institute studied pictures of the Martian surface snapped from orbit. He found features that are identical to those found where permafrost has melted here on Earth. The features include curved cliffs, channels, fields of rocky debris, and wider fans of debris like those formed by river deltas.
The features are found near the Martian equator, where temperatures are warmer than on the rest of the planet. The study says the features indicate that the water froze and thawed several times over a period of several million years.
Since water is necessary for life, these features -- and others that were also carved by flowing water -- might be good places to hunt for evidence of life in the planet's past.
Mars rises around 1 a.m. right now, and stands high in the southeast at first light. It looks like a bright orange star. It'll rise earlier and grow brighter throughout the rest of the year.
We'll have more about Mars tomorrow.
Script by Damond Benningfield, Copyright 2009
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