Astro News Briefs: December 9–15

Was Ancient Mars Sometimes a Sauna?

December 13, 2002 | Like all the inner planets, Mars took a heavy beating early in solar-system history, enduring dozens of collisions with asteroids 100 to 200 kilometers across. But a team of researchers now suggests that these titanic impacts did more than just rattle the red planet to its core — their energy may have briefly vaporized huge deposits of buried water and repeatedly enveloped Mars in a hot, vapor-charged atmosphere that drenched the surface with rain. By modeling the aftermath of an asteroid's impact with Mars, Teresa L. Segura (NASA-Ames Research Center) and three colleagues found that superheated debris would cover the entire planet to depths of up to 100 meters. As they describe in the December 6th issue of Science, this cocoon of hot rock would drive any near-surface ice into the atmosphere as water vapor that would eventually rain out onto the landscape. The result is not the warm, clement Mars that biologists would prefer. Instead, they conclude, "We envision a cold and dry planet, an almost endless winter broken by episodes of scalding rains followed by flash floods."

A press release describing the results (which were also presented at last week's meeting of the American Geophysical Union) appear at