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Martian terrain sculpted by long wet periods |
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Written by Derek Kessler on
Thursday, 02 October 2008
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 Even though the Phoenix Lander has shown that Mars is pretty much as dry as we thought it was, a new study suggests that the massive valleys we see on the red planet now were carved out by wet and dry seasons much like Earth’s current deserts. This stands in stark contrast to theories that the networks of valleys were the result of short-lived catastrophic flooding that lasted from a few centuries to a few millennia. The latest models indicate that wet periods on Mars could have lasted longer than 10,000 years.
The study was conducted by University of California, Santa Cruz planetary sciences graduate student Charles Barnhart, along with Alan Howard of the University of Virginia and NASA scientist Jeffery Moore.
High-resolution imagery of Mars obtained by the flotilla of satellites currently orbiting the planet has shown that the landscape was clearly shaped by liquid runoff, rather than tectonic activity or Martians. The most likely source of runoff has always been water, though carbon dioxide has on occasion surfaced as part of a theory. According to the new proposal, the Mars of 3.5 billion years ago looked much like the deserts in the southwestern United States.
Previous leading theories posited that catastrophic flooding was triggered by asteroid impacts that breached underground aquifers and released torrents of floodwaters on the planet. However, such flooding would have wiped out such craters as they overflowed, meaning that the oldest craters seen on Mars today would not exist anymore. That led to the proposal of a seasonally wet and dry Mars, which permits for large-scale water erosion while still not totally wiping out surface features.
How long these wet and dry periods may have lasted is uncertain. Seasonally is obviously a possibility, but it is equally probable that the cycle frequency was much longer and associated with planetary warming triggered by outgassing from volcanic eruptions or large impacts, or even changes in the axial tilt of Mars.
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