Back in the Comet Business

摘要

The most ambitious mission ever to head for a comet is counting down just in time to lift astronomers' spirits. Comet scientists are still recovering from NASA's disappointing Contour mission, a comet-exploring satellite that stopped transmitting to Earth less than two months after its launch in July 2002. Now, a European Space Agency mission called Rosetta will try something never before attempted: landing on a comet. That comet is called Wirtanen, a great lump of ice, dust and rock 4,000 feet in diameter, that is hurtling through space at 84,000 mph. After launch (slated, at press time, for January 12, 2003), Rosetta will travel for some eight years, then match Wirtanen's speed and settle into the comet's orbit. Rosetta will first spend two years mapping Wirtanen's surface and then deploy a lander there, firing a harpoon into the comet to anchor itself in the virtually gravity-free environment. The lander's legs will screw themselves into the comet's surface to secure itself for about 60 hours of experiments.