Jan. 25, 2007 — Whatever happened to Mars' atmosphere, it didn't get blasted into space by the solar winds, conclude scientists in a new report.
Extrapolating information obtained by an instrument aboard Europe's Mars Express spacecraft, a team of Swedish and French scientists obliterated what had been considered a top theory to explain the global climate change Mars underwent sometime in its past that left it a cold and dry desert.
Carved channels, gullies and other surface features led scientists to conclude that Mars once had plenty of liquid water on its surface. But they are stumped to explain where it went.
An atmospheric change remains a likely explanation, but Stas Barabash of the Swedish Institute of Space Physics and colleagues conclude in a research paper published in this week's issue of Science that researchers will have to look beyond the bombardment of electrically charged solar wind particles to explain the atmosphere's erosion.
"Either other escape channels were or are operational — or water and carbon dioxide are stored in nonidentified reservoirs," on or beneath the planet's surface, Barabash wrote.
Work to find underground water reserves is under way by the Mars Express and NASA's new spacecraft, the Mars Reconnaissance Orbiter. So far, though, scientists can only account for a fraction of the water that would have been necessary to carve Mars' water-linked surface features.
"This result is rather more of a puzzle than a help because it raises more questions," Jeffrey Plaut, a planetary geologist with NASA's Jet Propulsion Laboratory in Pasadena, Calif., said in an interview with Discovery News.
Plaut, who is using another Mars Express instrument to look for water buried beneath the planet's crust, said it is important to investigate other ways Mars could have lost water molecules from its atmosphere.
Other explanations include the possibility of an asteroid strike or a series of strikes that catastrophically stripped the planet of its atmosphere.
"This (finding) doesn't close the door on atmospheric escape explaining the loss of water," Plaut said. "The evidence is convincing that a lot of water flowed across Mars at some point in its past. Now we see a tiny bit in the atmosphere and some deposits in the ground.
"What we, the Mars science community, are trying to do is answer the question of where did all the water go?"
