The new issue of Science (15 April 2011 vol 232 p 302) discusses the current status of analyses of the samples returned from the asteroid Itokawa. It is a solid scientific success. The results were presented by Japanese scientists at the Lunar and Planetary Science Conference in The Woodlands, Texas, from 7 – 11 March 2011.
Analysis has confirmed that the S-type class of asteroids covered by a mysterious discoloration is the source of the most common meteorite that falls to Earth. Decades ago, research had suggested the composition of these asteroids was different from chondrite meteorites.
However, by 2001, Richard Binzel and others at MIT had concluded from telescopic observations that Itokawa belongs to the distinctive LL subclass of ordinary chondritic asteroids that had been “weathered” by exposure to space.
The first task was to remove any particles from the collection mechanism, which had malfunctioned in spectacular fashion. A specially designed extraction tool was a failure. A Teflon spatula was a bit better, but the best result came from striking the overturned canister with a screwdriver. 20 sharp raps did the trick. About 1500 particles from Itokawa were recovered. All smaller than 100 micrometers.
Researchers across Japan took 52 of these particles and applied a range of microanalytical techniques – XRD, XRF, UMT, FIB, TEM, SEM, EPMA and SIMS. This alphabet soup clearly showed that Itokawa was a space-weathered ordinary LL chondrite asteroid. A great win for Hayabusa.
Additional research is now underway to determine what sort of space weathering is involved in producing the discoloration.
Previous NSS Phoenix blog entries about the intrepid Hayabusa can be found at: