• E-mail
• Print
• Comment
• Font Size
• Digg
• del.icio.us
• Discuss article

Mars Answers Spur Questions Evidence of Water Deepens Mystery of Planet's History

Posted on: Friday, 12 November 2004, 09:00 CST

Five spacecraft are circling Mars and creeping across its ruddy surface, looking for traces of long-gone waters and signs that the cold, arid planet may once have been hospitable to life. The robotic martian invasion - three orbiters and two six-wheeled rovers - has already uncovered strong evidence that water once flowed on Mars and is now locked in subsurface ice. But big questions about water on Mars remain. When did it flow? How long did it last? How much was there? Where did it come from? Where did it go? Perhaps the most tantalizing question: Were there long-lived watery environments where microbial life could have gained a foothold? "We believe there was persistent water, but we need to figure out how to get the (ancient Mars) climate to support water on the surface," said Daniel McCleese, chief Mars scientist at NASA's Jet Propulsion Lab. McCleese and scientists from all five current Mars spacecraft spoke Wednesday morning at a meeting ofthe Geological Society of America in Denver. Today's Mars is too cold to allow liquid water to persist on the surface. After NASA's Viking orbiters captured images of sinuous, apparently water-carved channels and flood deposits in the 1970s, many researchers began to suspect that early Mars had a dense carbon dioxide atmosphere that warmed the surface and permitted liquid water

. But evidence for a warm, wet early Mars with a dense atmosphere has been scanty, McCleese said. One current idea is that young Mars was cold and wet, with ice-covered oceans and waterways, he said. Photos returned by the first Mars probes showed a crater- blasted surface that resembled the moon. But recent missions have revealed a martian surface that is far more complex than the moon's, with evidence for repeated episodes of sediment deposition and erosion, said Michael Malin, head of the camera team on NASA's Mar Global Surveyor mission. Mars craters have been filled with mounds of sediment that were later exhumed by erosion, only to be reburied and then re-excavated. Down-cutting erosion revealed stacks of layered deposits. "We don't know where it (the sediment) came from, how it got there, and where it went," Malin said. "What does all this work? We think it's water." Global Surveyor was built by Lockheed Martin Space Systems in Jefferson County. It was launched in November 1996 and is still mapping the surface. Lockheed Martin also built Odyssey, launched in 2001 and still orbiting the planet. Shortly after its arrival at Mars, Odyssey found subsurface ice near both martian poles. Odyssey's gamma ray spectrometer determined that the ice extended at least a yard beneath the surface. "The big question is, does it go deeper and is this a sign of a much thicker ice layer?" said JPL's David Senske. The European Space Agency's Mars Express orbiter will try to answer that question with a radar system designed to probe more than a mile beneath the martian surface. Mars Express arrived last December. But due to technical glitches, mission engineers haven't been able to unfurl its radar antennas. They hope to do so in March, said JPL's Jeffrey Plaut, a member of the Mars Express science team. While the orbiters circle overhead, the twin Mars Exploration Rovers continue to roll across the surface. Both rovers arrived in January and both have found evidence that waters once soaked martian rocks. "We suspect it was a shallow-water environment with intermittent wetting and drying," said Cornell University's Steven Squyres, the lead rover scientist. Next year, NASA's Lockheed Martin-built Mars Reconnaissance Orbiter will launch on a mission to snap the sharpest-ever pictures of the red planet's surface. In 2007 another Lockheed Martin craft, Phoenix, will land in a polar region and attempt to dig into subsurface ice. In 2009, NASA's Mobile Science Laboratory - as big as a Volkswagen Bug - will be launched. Science instruments for the lab will be selected in about two weeks. Beyond that, NASA is planning a mission to bring Mars rocks and soil to Earth. And President Bush has called for human missions back to the moon and on to Mars. McCleese said the best-guess date on a human Mars mission is 2030.

Source: Rocky Mountain News

More News in this Category