Late last year, astronomers noticed an asteroid named Scheila had unexpectedly brightened, and it was sporting short-lived plumes. Data from NASA's Swift satellite and Hubble Space Telescope showed these changes likely occurred after Scheila was struck by a much smaller asteroid.

This visible-light image of asteroid (596) Scheila was taken with Hubble's Wide Field Camera 3 on Dec. 27, 2010, when the asteroid was approximately 217 million miles away. The asteroid is surrounded by a C-shaped cloud, or coma, of dust particles. The asteroid body, which is approximately 70 miles across, appears star-like because it is overexposed so that the faint dust can be imaged.

http://hubblesite.org/news_release/news/2011-13