This is 253 Mathilde, a heavily cratered mainbelt asteroid viewed in June 1997 by the Near Earth Asteroid Rendezvous spacecraft. Mathilde is made of dark, carbon-rich material which is relatively unchanged from 4.6 billion years ago. Other asteroids have undergone thermal metamorphism, and a few are largely metallic. We are now beginning a two-year radar survey of mainbelt asteroids, focusing on carbonaceous objects like Mathilde.
In August 2002 the National Science Foundation awarded Dr. Chris Magri a three-year grant of $127,330 to continue his research on asteroids. Dr. Magri and his collaborators use the world’s most powerful radar telescope, the Arecibo Observatory in Puerto Rico, to study dark, carbon-rich asteroids in the main belt between Mars and Jupiter; these objects are geochemically primitive links to the formation of the solar system. He recently led a two-year radar survey of 55 main-belt asteroids and is currently preparing the results for publication. Dr. Magri also was one of nine coauthors of the cover article for the May 5, 2000 issue of Science magazine; the team analyzed radar images of asteroid 216 Kleopatra in order to determine that it is a highly exotic object, a spinning metallic dog bone the size of New Jersey. Kleopatra presumably resulted from collision(s) between shards of the nickel-iron core of a large protoasteroid which suffered a catastrophic impact. It is the most bifurcated known object in the solar system and is the first main-belt asteroid to have its shape determined via radar.
Here is a radar Doppler spectrum of the mainbelt asteroid 105 Artemis. The two curves represent two polarizations of radio light: the strong echo is mostly due to smooth surfaces, while the weak one is produced by rocks lying atop or buried just below the asteroid’s surface. (Here’s a clearer view.)
4769 Castalia is a near-Earth asteroid whose appearance has been reconstructed from radar data. It is a double-lobed “contact binary” which probably formed in a weak collision. We are currently using new data to construct the first such models for mainbelt asteroids.
For more information, contact Dr. Chris Magri