THIS WEEK IN SCIENCE

摘要

With a diameter of 265 kilometers, 2 Pallas is one of the lar.gest bodies in the main aster-. oid belt. Now Schmidt et al. (p. 275) Have characterized its surface and shape, using images from the Hubble Space Telescope. Color.variations and topography were revealed that are possibly linked to the asteroid's thermal evolution and to the. formation of its orbital family-the population of asteroids that share the same properties as 2 Pallas and-are thought to be the fragments of a collision. In particular; a large-impact crater was' observed that could represent the source of the Pallas family. 2 Pallas represents the third' intact protoplanet in-the main asteroid belt, joining asteroids 1 Ceres and 4 Vesta.