A REMOTE region of Antarctica has yielded what may be the best-preserved comet dust yet found, perhaps in better condition than the samples NASA鈥檚 Stardust mission brought back from a comet鈥檚 tail.
A team of meteorite experts led by Jean Duprat of the University of Paris South, France, found the dust in snow collected near Concordia base, high on the Antarctic plateau. When they melted the snow and filtered out anything more than 25 micrometres across, almost a third of the particles they found were from space. 鈥淚t鈥檚 the only place on Earth where you鈥檝e got this number,鈥� Duprat says.
鈥淪ome of the particles are half a millimetre across, larger than those collected by balloons and planes in the stratosphere鈥�
Advertisement
Preliminary tests show that some of the particles have a composition close to what one would expect from comet dust. Many of them seem to be in remarkably good condition: fluffy, fragile grains that somehow entered the atmosphere without vaporising or melting. Presumably they arrived slowly, travelling on a similar orbit to Earth鈥檚.
Comets are thought to have changed very little over the last 4 billion years, so their composition should hold clues to the origin of the solar system. The results will be published in a future issue of Advances in Space Research.
Previous expeditions have gathered micrometeorites from elsewhere in Antarctica and from Greenland, but most were in old, compacted ice and had been significantly altered by the elements. Duprat鈥檚 team took extra care not to damage the most fragile grains. 鈥淭he thing that鈥檚 wonderful is that they have been finding these very fluffy particles,鈥� says Susan Taylor of Dartmouth College in New Hampshire, who pioneered the collection of micrometeorites from Antarctic snow. Some are as much as half a millimetre across, larger than similar particles collected by balloons and planes in the stratosphere, according to Duprat. That makes them easier to analyse.
Duprat hopes to compare his grains with those from NASA鈥檚 Stardust mission, which landed in January carrying samples collected directly from the tail of comet Wild 2. The dust has yet to be extracted from the spacecraft鈥檚 collector, but it may turn out to be in relatively poor shape, as catching particles at high speed could damage them, Duprat says.
