Postcards from Space
Rao, Joe, Natural History
Fifty years from now, the year 2004 may well be remembered as a high point in space and planetary science. Here are some late dispatches.
Intended primarily to find out if and where water once existed on the now-dry Martian surface, the two Mars Exploration Rovers (Spirit and Opportunity) that landed on the planet this past January continue to photograph their surroundings and check out the rocks and soil. Both rovers have found hematite, often a mineralogical sign of water. Investigators say it's clear that parts of Mars's surface were once sopping wet and, at least for some time, habitable. The rovers were expected to poop out in April or so, but as of press time, they're still on a roll. (marsrovers.jpl.nasa.gov/home/)
Lord of the Rings
Meanwhile, the Cassini spacecraft has been orbiting Saturn since June 30. It has captured the closest-ever look at the planet's icy rings, and provided new insights on Saturn's vast magnetosphere-the invisible bubble of magnetic fields, electric currents, and trapped radiation that surrounds the planet. On Christmas Eve 2004 the Huygens probe, which has been hitching a ride with Cassini, will separate from the mother ship and, three weeks later, plunge into the nitrogen- and methane-rich atmosphere of Saturn's largest moon, Titan-where signs of former or (who knows?) present-day life might be lurking. (saturn.jpl.nasa.gov/home/index.cfm)
On January 2, 2004, NASA's Stardust spacecraft, launched in February 1999, came within 150 miles of a several-mile-wide comet named Wild 2. …