Goddard Space Flight Center, Greenbelt, Maryland 20771ENGINEERING COLLOQUIUMMonday, December 4, 2000 / 3:30 PM, Building 3 AuditoriumAndrew F. Cheng"Scientific Highlights of NEAR Shoemaker"ABSTRACT -- The NEAR Shoemaker spacecraft entered orbit around the near Earth asteroid 433 Eros on February 14, 2000. Since then, intensive observations from orbit have revealed that Eros is a complex and fascinating object. NEAR Shoemaker has measured the first x-rays and obtained the first laser altimetric data from an asteroid. Eros has a highly irregular shape, with a maximum linear dimension of 32.7 km but a minimum diameter of 7 km from the bottom of the 5 km crater to the bottom of the saddle-shaped depression on the opposite side of the asteroid. The average density of Eros is about that of Earth's crust, and it is almost uniform, but there are suggestions of a small density variation. The bulk elemental composition of Eros indicates that Eros is not a differentiated body, so it never underwent melting and separation into distinct compositional layers as did the Earth and the other terrestrial planets. A primitive, undifferentiated composition is also inferred from visible and near infrared spectra. We are still searching for evidence of partial melting and small scale compositional heterogeneity. The composition of Eros may be consistent with that of the important class of primitive meteorites known as ordinary chondrites. We are also searching for intrinsic magnetization of Eros. The surface of Eros is surprising in many ways. There is a pervasive global fabric consisting of a variety of ridges, grooves, and chains of pits or craters. Many craters have shapes that imply significant strength in the surface material of Eros. Some regions appear to be extensively resurfaced. Several landslides have been identified on Eros. Some topographic features, including a ridge system several kilometers long and over 100 m high in places, indicate tectonic deformations. Contrary to theoretical predictions, Eros does not appear to be a loosely bound collection of much smaller component bodies. Some global scale linear features suggest that Eros may once have been part of a much larger body. SPEAKER -- Dr. Andrew F. Cheng
is a Principal Professional Staff member at the Johns Hopkins University
Applied Physics Laboratory, where he is currently supervisor of the Theoretical
Space Physics section. He obtained an AB in physics from Princeton
University in 1971 and a Ph. D. in physics from Columbia University in
1977. His scientific interests include surface processes on small
bodies, space plasma and astrophysical fluid dynamics, interactions of
plasmas with atmospheres and solid surfaces, and magnetospheric physics.
He is the Project Scientist for the Near-Earth Asteroid Rendezvous mission
of the NASA Discovery Program. He is the Orbital LIDAR scientist
on the ISAS-NASA MUSES-C mission to a near-Earth asteroid and a co-investigator
on the CASSINI mission to Saturn. He was an Interdisciplinary Scientist
on the GALILEO mission to Jupiter. He is a fellow of the American
Physical Society and a former editor of EOS-Transactions of the American
Geophysical Union. He has served as an associate editor for the Journal
of Geophysical Research and for Geophysical Research Letters. He
has served on several NASA and National Academy of Science advisory committees.
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