Mars Climate Change may thicken atmosphere
Study Suggests Mars Ice Caps Eroding
By PAUL RECER, AP Science Writer
WASHINGTON (AP) - Vast fields of carbon dioxide ice are eroding from the poles of Mars, suggesting that the climate of the Red Planet is warming and the atmosphere is becoming slightly more dense.
Experts say that over time such changes could allow water to return to the Martian surface and turn the frigid planet into a ``shirt-sleeve environment.''
Michael A. Caplinger, a scientist with Malin Space Science Systems, said that if the rate of carbon dioxide erosion from the Mars poles continues for thousands of years, ``then it could profoundly amend the climate of Mars.''
``You would go from having to wear a spacesuit to just wearing a coat and an oxygen atmosphere,'' said Caplinger.
Caplinger is co-author of a study appearing in the journal Science that analyzes photos of Mars taken by an orbiting spacecraft. The photos were taken in 1999 and in 2001, a period of time that represents one Martian year. Mars is farther from the sun than the Earth and it takes the Red Planet about 23 months to complete one year, a single solar orbit.
Observers have long known that in the Martian winter there is a snow of carbon dioxide caused as temperatures plunge and the gas freezes out of Mars' thin atmosphere.
But the new study suggests that a dense cap of frozen carbon dioxide thought to be permanent at each of the Mars poles may not be all that permanent, said Caplinger.
``It is eroding away at a rapid pace and is going to continue to do that,'' said Caplinger. ``This is not a seasonal change.''
He said the photos suggest that the polar caps are dense slabs of frozen carbon dioxide that may have been deposited over centuries, much like the way seasonal snow on Earth accumulates to form a glacier.
``This stuff has been there for quite a while,'' he said. ``It is packed down and very smooth. We don't see evidence that it is blowing around or drifting.''
Instead, said Caplinger, the glacier-like carbon dioxide ice is eroding, rather like the way a glacier melts on Earth.
The key clue, he said, comes from examining the light patterns on pits at the Martian south pole. Comparing pictures taken a Martian year apart show that the pits are getting wider and deeper as a result of the retreat of the carbon dioxide ice, said Caplinger.
As the C02 ice erodes, it adds carbon dioxide to the Martian atmosphere, causing the ``air'' to get thicker over time. This would enable the planet to hold more of the sun's heat and, perhaps, eventually warm the whole planet enough for water to return to the Martian surface.
Caplinger said it is not known if there is enough carbon dioxide in the polar caps to bring about such an atmospheric change.
But his co-author, Michael C. Malin, said in a statement that if the atmosphere of Mars becomes dense enough, it would ``permit liquid water to persist at or near the surface.''
Other studies have shown that Mars was once awash with great basins of water, but the water is thought to have disappeared or become subsurface ice as the planet cooled and developed a thin C02 atmosphere.
Some experts suggested that any speculation about a Martian climate change is premature.
``This is a really neat observation,'' said Allan H. Treiman of the Lunar and Planetary Institute in Houston. But he said the pictures span a time too short to make predictions about permanent changes in the Mars climate.
``We don't have enough data on Mars to draw any clear conclusions about climate change,'' he said.