Rovers, Orbiter Dig in to (Wet?) Martian History
(From the March/April 2004 issue of StarDate magazine)
When historians of the future write about the early days of planetary
exploration, they almost certainly will devote a few pages to events on Mars
in late 2003 and early 2004. Never had so many spacecraft taken aim at a
single world in so short a time: five probes in just seven weeks. Some
didn’t make it, some did, and some still face tough challenges as they try
to provide clues to help scientists solve two Martian mysteries: What
happened to the planet’s water, and did life ever evolve there?
Europe’s Mars Express quickly confirmed that much of the planet’s south
polar ice cap consists of frozen water. Until recently, scientists thought
the ice caps were made mainly of frozen carbon dioxide with only a small
amount of water underneath. But readings by other orbiters suggested that
water could be the main ingredient in the ice caps, and Mars Express agreed.
Next, the craft will use a powerful ground-penetrating radar to look for
evidence of frozen water mixed with the top few feet of soil across most of
the rest of the planet. Other craft have found strong evidence of frozen
water in the top layers of soil near the poles, but Mars Express will probe
deeper.
NASA’s twin rovers, Spirit and Opportunity, won’t dig far, but they will
look for signs of ancient water in soil and rocks near the surface. Spirit
landed in a possible lakebed, although images transmitted before its
computer memory went on the blink suggested any sediments were covered by
volcanic rock. Opportunity plopped into a small crater, and scientists hoped
exposed layers of bedrock on the crater wall might show signs of layering or
chemical weathering from exposure to water.
Even as Spirit was making its first move across the Martian landscape,
President George Bush called for a new human space initiative that would
culminate with a manned mission to Mars. Human geologists could dig a little
deeper and rove a little farther in the quest for Mars water. So Spirit and
the other robotic missions have two chances to rewrite the history of
planetary exploration — by discovering strong evidence of water, or by
helping to prepare the way for human explorers in the decades to come. -- Damond Benningfield
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