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JET PROPULSION LABORATORY
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PHOTO CAPTION                                     GALILEO
June 11, 1992                                     P-40450-C
                              TOP                 GLL/GA5

     This picture of asteroid 951 Gaspra is a combination of the
highest-resolution morphology and color information obtained by
the Galileo spacecraft during its approach to the asteroid on
October 29, 1991.  The Sun is shining from the right; phase angle
is 50 degrees.  The base image is the best black-and-white view
of Gaspra (resolution 54 meters/pixel) on which are superimposed
the subtle color variations constructed from violet, green, and
near-infrared (1000 nanometers) inages taken in an earlier
sequence at a resolution about 164 meters/pixel.

     The very subtle color variations on Gaspa's surface have
been artificially exaggerated here; to first order Gaspra's color
is fairly homogeneous over the surface.  However, subtle albedo
and color variations do occur and are correlated with surface
topography in a significant way.  In this false-color view, the
bluish areas represent regions of slightly higher albedo, which
are also regions of slightly stronger spectral absorption near
1000 nanometers, probably due to the mineral olivine.  These
bluish areas tend to be associated with some of the crisper
craters and with ridges.  The slightly reddish areas, apparently
concentrated in topographic lows, represent regions of somewhat
lower albedo and weaker absorption near 1000 nanometers.  In
general, such patterns can be explained in terms of greater
exposure of fresher rock in the brighter bluish areas and the
accumulation of some regolith materials in the darker reddish
areas.

     Gaspra is an irregular body with dimensions about 19 x 12 x
11 kilometers (12 x 7.5 x 7 miles).  The portion illuminated in
this view is about 18 kilometers (11 miles) from lower left to
upper right.  

     This color picture results from a joint effort by image
processing groups at the U. S. Geological Survey in Flagstaff,
Arizona, Cornell University in Ithaca, New York, and JPL.  The
Galileo project, whose primary mission is the exploration of the
Jupiter system in 1995-97, is managed for NASA's Office of Space
Science and Applications by the Jet Propulsion Laboratory.

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