So far the research has resulted in several major discoveries, including confirmation that the moon harbors the biggest crater in the solar system, the South Pole-Aitken Basin. The massive structure on the moon's far side, first identified by images taken in previous lunar research, is 7.4 miles deep and 1,550 miles wide. On Earth it would stretch from the East Coast to the Rocky Mountains, said Dr. Zuber, whose lunar research fits the same motif as the upcoming asteroid and Mars probes. All three projects strive to understand the physics of solar system bodies. The spacecraft will rendezvous with Eros, a rocky cigar-shaped mass that represents a tantalizing time capsule for scientists trying to learn more about the early solar system.
Asteroids are at least as old as the moon.
But the moon has been struck by so much debris that its crust has been melted many times, producing a complex history of chemical change. Asteroids, however, are much smaller targets. They have not been bombarded by so many objects and are less tainted by the effects of time. It is scheduled for a February 1996 launch and for a December 1998 rendezvous with Eros. NASA plans to launch the Mars Global Surveyor in November 1996.