A frosty finding

摘要

The asteroid belt is classically considered the domain of rocky bodies, being too close to the Sun for ice to survive. Or so we thought - not only is ice present, but at least one asteroid is covered in it.rnFrom high atop the summit of Mauna Kea, where, fittingly, snow often falls in the otherwise tropical Hawaiian islands (Fig. 1), two teams, Rivkin and Emery (page 1322 of this issue) and Campins et al. (page 1320), have found evidence of ice in a similarly unexpected place: the main asteroid belt, which lies between the orbits of Mars and Jupiter. They report the discovery of a frost coating on the surface of 24 Themis, one of the largest asteroids in the asteroid belt.