MOON rocks were just the start. Now NASA wants to add cometary dust to its collection of celestial rubble. In February 2004 it will send a probe into orbit to capture a little bit of Comet P/Wild-2 and bring it back to Earth.
The probe, called Stardust, will fly within 100 kilometres of the comet. Three times during its mission – once as it approaches the comet, once in the thick of the dust, and again as it heads away – a collecting plate about a metre across will pop out from the back of the probe. A gel covering the collecting plate will trap dust expelled from the comet.
ÒÁÈ˾þÃs at the University of Washington in Seattle, who are in charge of Stardust, hope to trap about 10 000 dust particles larger than 15 micrometres across and a few as large as 0.25 millimetres across.
A capsule will carry the collecting plate back to Earth in January 2006. Because P/Wild-2 is a “fresh” comet – one that has made few passes close to the Sun – scientists believe its debris will reveal the early composition of our Solar System.
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