Researchers on the Mars Exploration Rover team feel these observations of this site point to an area once drenched in water, providing an environment that could have supported life. The body of water gradually evaporated away, due to the thin Mars atmosphere, leaving high concentrations of salt behind and several telltale mineral deposits and geologic formations. Because the observed signs point to an area that once was a lake, or large body of water, it would be a good choice to further explore the Meridiani Planum for fossils or other relics of previous life forms.
But to Knauth, Burt and Wohletz the geologic features at the Opportunity landing site can also be explained as being artifacts of a meteorite strike rather than a one-time lakebed.
"When a meteorite hits there is a tremendous blast, like a nuclear explosion," Knauth said. "On a planet with an atmosphere, around the base you get a turbulent ground-hugging cloud of debris that goes out and makes a sedimentary deposit. You get deposits that can go up to almost 100 kilometers from big volcanoes. A big [meteorite] impact can provide deposits over tens of thousands of square kilometers.
"Mars is cratered from one end to the other. All of these should have made base surges," Knauth said.
Upon examining the evidence, the researchers believe the sediments and structures at the Opportunity landing site are more likely caused by a base surge than an evaporated lake. Some of the questions concerning the observed sediments include a mixing of evaporative salts, textures of the sediments and the existence of small spheroid concretions at the landing site.
"The mixed chemistry of the salts is all wrong at the Opportunity site," Burt said. "If it were a large lake that slowly evaporated, then the salt deposits would be more uniform going from least soluble (calcium sulfate, jarosite) to most soluble (
'"/>
Contact: Skip Derra
skip.derra@asu.edu
480-965-4823
Arizona State University
21-Dec-2005