Microscopic images in false colors. (a) One of investigated Itokawa grain. The mineral troilite (FeS, violet) is surrounded by silicate minerals (green). (b) Troilite surface (violet) with iron whiskers (blue). (c) An enlarged image of an iron whisker. Credit: Toru Matsumoto
Itokawa would normally be a fairly average near-Earth asteroid—a rocky mass measuring only a few hundred metres in diameter, which orbits the sun amid countless other celestial bodies and repeatedly crosses the orbit of the Earth. But there is one fact that sets Itokawa apart: in 2005 it hosted a visit from Earth. The Japanese space agency JAXA sent the Hayabusa probe to Itokawa, which collected soil samples and brought them safely back to Earth—for the first time in the history of space travel. This valuable cargo arrived in 2010 and since then, the samples have been the subject of intensive research.