Donald Savage
Headquarters, Washington, DC                			Apr. 19, 1995  (Phone:  202/358-
1547)               

Tammy Jones
Goddard Space Flight Center, Greenbelt, MD
(Phone:  301/286-5566)

Ray Villard
Space Telescope Science Institute
(Phone:  410/338-4514)

RELEASE:  95-183 (52)

NASA'S HUBBLE TELESCOPE MAPS THE ANCIENT SURFACE OF VESTA

       Hubble Space Telescope images of the asteroid Vesta are providing astronomers with 
a glimpse of the oldest terrain ever seen in the solar  system and a peek into a broken-off 
section of the "mini-planet" that   exposes its interior.

       Hubble's pictures provide the best view yet of Vesta's complex surface, with a 
geology similar to that of terrestrial worlds such as Earth or Mars.  The asteroid's ancient 
surface, battered by collisions eons ago, allows astronomers to peer below the asteroid's 
crust and into the past.   

       Astronomers also believe that fragments gouged out of Vesta during ancient 
collisions have fallen to Earth as meteorites, making Vesta only the fourth solar system 
object, other than Earth, the Moon and Mars, where scientists have a confirmed 
laboratory sample.  (About   50-60 other meteorite types are suspected to have come from 
asteroids, but positive identifications are more difficult to make.) 

       "The Hubble observations show that Vesta is far more interesting than simply a 
chunk of rock in space as most asteroids are," said Ben Zellner of Georgia Southern 
University.  "This qualifies Vesta as the   'sixth' terrestrial planet."

       No bigger than the state of Arizona, Vesta offers new clues to the origin of the solar 
system and the interior makeup of the rocky planets.  "Vesta has survived essentially 
intact since the formation of  the planets," Zellner said.  "It provides a record of the long 
and complex evolution of our solar system."

       Resolving features down to 50 miles across, Hubble reveals a surprisingly diverse 
world with an exposed mantle, ancient lava flows and impact basins.  Though only 325 
miles (525 kilometers) across, it once had a molten interior.  This contradicts 
conventional ideas that asteroids essentially are cold, rocky fragments left behind from 
the early days of planetary formation.

       Besides providing scientists with direct samples, Vesta's chipped surface allows 
Hubble to study the asteroid's rocky mantle, giving scientists a unique opportunity to see 
what a planet looks like below the crust.  "Our knowledge of the interior composition of 
the other   terrestrial worlds, the Moon, Mars, Venus, Mercury and even Earth, depends 
heavily on theory and inference," Zellner said.  "Vesta allows   us to actually see the 
mantle and study pristine samples in our  laboratories." 

       Before these observations, only the smaller and less geologically diverse asteroids, 
Ida and Gaspra, have been observed in detail by the Jupiter-bound Galileo spacecraft.  
Unlike Vesta, these smaller objects are pieces torn off larger bodies by collisions that 
occurred perhaps only a few hundred million years ago. 

       The Space Telescope Science Institute is operated by the Association of Universities 
for Research in Astronomy, Inc. (AURA) for NASA, under contract with the Goddard 
Space Flight Center, Greenbelt, MD.  The Hubble Space Telescope is a project of 
international cooperation between NASA and the European Space Agency (ESA).

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