March 30, 2001
Colloquium Speaker: Andrew F. Cheng
Dr. Andrew F. Cheng is a principal staff physicist in the Space Department of the Johns Hopkins University Applied Physics Laboratory. He received a Ph.D. degree in physics from Columbia University in 1977. He was a post-doctoral fellow at AT&T Bell Laboratories and an assistant professor of physics at Rutgers University prior to joining the Applied Physics Laboratory in 1983. He has been an Interdisciplinary Scientist on the Galileo mission to Jupiter, a Co-Investigator on the Cassini mission to Saturn, and a team member on the MUSES-C mission to a near-Earth asteroid. He has been the Project Scientist for the Near Earth Asteroid Rendezvous (NEAR) mission to asteroid Eros. He is currently a science team member on the Mercury Surface, Space Environment, Geochemistry, and Ranging (MESSENGER) and the Comet Nucleus Tour (CONTOUR) missions. Dr. Cheng is a fellow of the American Physical Society and a member of the American Geophysical Union and the American Astronomical Society.
The Near Earth Asteroid Rendezvous mission has spent the past year exploring the near-Earth asteroid 433 Eros, at first by remote sensing from orbit as originally designed, but then continuing after NEAR landed on the asteroid surface. NEAR is silent now, but it has transformed our understanding of asteroids and their relations to meteorites. Major findings include the following: Eros is a primitive asteroid that has not differentiated; the meteorites most similar in composition to Eros are the low-iron ordinary chondrites; Eros is a consolidated body formed as a collisional fragment of a larger parent body; Eros is not a rubble pile but is heavily fractured and has an average density about that of Earth¹s crust; Eros has a complex, mobile regolith, with a surprising deficiency of small craters and an unexpectedly large abundance of blocks; Eros is non-magnetic and is less magnetized than most meteorites.