NASA just press-released some recent new views of Vesta, one of the largest denizens of the asteroid belt, soon to be visited by the Dawn spacecraft. The movies were taken in short wavelengths (ultraviolet and blue) by Hubble's relatively new camera, the Wide Field and Planetary Camera 3. The movie is terrific; it really gives a sense of the asteroid's shape. Is it me, or is there a really big, deep crater on the equator? Or is it just an especially dark patch of material?
redit: NASA / ESA / STScI / UMd
stronomers combined 146 exposures taken by NASA's Hubble Space Telescope to make this 73-frame movie of the asteroid Vesta's rotation. Vesta completes a rotation every 5.34 hours. The images were taken in near-ultraviolet and blue wavelengths, so the movie is not representative of what the human eye would see. Dark areas are interpreted to be regions of basalt; red areas are likely "regolith" or dust. The observations were made on February 25 and 28, 2010.
Here's a still from the same set of observations:
The research on these images was published in Icarus in July by Jian-Yang Li et al.: "Photometric mapping of Asteroid (4) Vesta's southern hemisphere with Hubble Space Telescope". I'm sure I could find the answer to my question about that equatorial dark patch in this paper -- but don't have time to read it just now, unfortunately.