The site where the Mars Exploration Rover Opportunity landed has sediments and layered structures that are thought to be formed by the evaporation of an acidic salty sea. The prevailing thought is that when this Martian sea existed it may have supported life forms and thus would be a prime site to explore for fossils.

However, ASU geologists L. Paul Knauth and Donald Burt, who along with Kenneth Wohletz of Los Alamos National Laboratory, say that base surges resulting from massive explosions caused by meteorite strikes offer a simpler and more consistent explanation for the rock formations and sediment layers found at the Opportunity site. The researchers published their findings in the current issue of Nature.

The research could impact where and how scientists continue their exploration of Mars in search for past life forms.

Impact surges "present a simple alternative explanation involving deposition from a ground-hugging turbulent flow of rock fragments, salts, sulfides, brines and ice produced by a meteorite impact," the three state in their article "Impact Origin of Sediments at the Opportunity Landing Site on Mars."

"Subsequent weathering by inter-granular water films can account for all of the features observed without invoking shallow seas, lakes or near surface aquifers," they added. "Layered sequences observed elsewhere on heavily cratered Mars and attributed to wind, water or volcanism may well have formed similarly."

When the Opportunity lander touched down on the Meridiani Planum in January 2004, it began a very important period in planetary exploration. The rover has operated for nearly two years -- when it was designed to operate for 90 days -- and has returned many breathtaking images of the Martian surface, as well a
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Contact: Skip Derra
skip.derra@asu.edu
480-965-4823
Arizona State University
21-Dec-2005