Vesta, one of the brightest main belt asteroids, as imaged with the
Keck Adaptive Optics system on its second night of operation. Images in
three bands (J=1.25 microns, H=1.65 microns and K' = 2.1 microns) were
used to produce a true color image. The open loop (no AO correction) image
is shown in the lower right hand side. The top row of images shows the
results of deconvolution (i.e., the estimate of the object which, when
convolved by the PSF - shown in the inset - most accurately reproduces
the data). In the true color image, red represents K; green, H; and blue,
J. The albedo at 1.2 microns is dominated by the reflection of pyroxene
while at 2.1 mostly by that of olivine. Thus, a very blue area shows
a concentration of surface pyroxene, and red, a concentration of olivine.
This animated K band image is made of a series taken over a 20 minute interval. It is difficult to determine the rotation axis (Vesta rotates every 5.34 hours), because of the short sampling interval, so more data will be acquired during the next engineering run. However the fact that we can follow dark and light areas would seem to confirm the reality of the structures seen in the deconvolved images.