Arizona researchers challenge Mars water theories
U.S. Water News Online
TUCSON, Ariz. -- Studies by University of Arizona scientists are challenging theories that water formed gullies found on Mars.
The Arizona studies suggest the gullies on crater walls probably were carved by carbon dioxide, not water. Further, they suggest that features thought to be shorelines were shaped by tectonic forces, not ancient oceans.
Don Musselwhite, Tim Swindle, and Jonathan Lunine of the university's Lunar and Planetary Laboratory published their hypothesis in the April 1 issue of Geophysical Research Letters.
The water theory arose after images from the Mars Surveyor spacecraft showed what appeared to be young features such as sand dunes.
Swindle said the concept bothered him immediately.
``When I saw that, I went, 'Wait a minute,''' Swindle said. ``What bothered me was that you have the very coldest places on the planet being touted as the very most recent places with recent liquid water.''
The gullies are found near Mars' south pole, where temperatures range from about minus 80 to minus 130 degrees Fahrenheit, cold enough to actually freeze the carbon dioxide that prevails in the martian atmosphere, he said.
In the winter, it gets so cold that carbon dioxide goes directly from gas to dry ice and fills up pore spaces in rocks below the surface. At a depth of about 100 meters below these crater walls, there is enough pressure that when the temperatures rise in the spring, the pressure in the pores builds up enough to allow the frozen carbon dioxide to turn into a liquid.
``Generally, it just evaporates, but as the pressure is building and the walls are thinning, you have liquid CO2 inside a bottle of dry ice and eventually it pops the cork,'' Musselwhite said. ``It vaporizes as it starts to flow and turns to a slurry of rock debris and dry ice snow.''
On the other side of Mars, in what is the smoothest surface known in the solar system, an ocean is thought to have formed shorelines.
Paul Withers, a UA doctoral student in planetary sciences, studied topographic data from the Mars Orbiter Laser Altimeter this summer with an MIT researcher at NASA's Goddard Space Flight Center.
The features were consistent with a shoreline at first glance.
But Withers said that on further inspection, it became clear the features had little ridges. That would mean that receding water would have had to miraculously avoid a ridge while making the area behind it flat, he said.
Withers and his co-researcher realized the wrinkled features looked more like they were caused by tectonic shifts resulting from volcanic activity.
Return to the U.S. Water News Archives page Or Return to the U.S. Water News Homepage
Editor@uswaternews.com
*Your Name:
*Your Email:
*Friend's Email:
Use a comma to separate e-mail addresses:
*Your Comments:
Hi, I thought you might like to read this article.
*Required Fields