Ice on asteroid 24 Themis

Two groups, both using the NASA Infrared Telescope Facility (IRTF) on Mauna Kea in Hawaii but independently, have obtained infra red spectra of the main-belt asteroid 24 Themis consistent with the widespread presence of a frosty coating containing water ice and organics. Although the presence of water on the surface of some asteroids had been inferred from the comet-like activity of several small asteroids, these are the first actual measurements of water and organics in the asteroid belt. The presence of surface ice is particularly surprising because of the relatively short lifetime that exposed ice has at this distance from the Sun — between the orbits of Mars and Jupiter. [Letters pp. 1320, 1322; News & Views p. 1286; www.nature.com/podcast]