Original Caption Released with Image:
These color visualizations of the Moon were obtained by the Galileo spacecraft as it left the
Earth after completing its first Earth Gravity Assist. The image on the right was acquired at 6:47
p.m. PST Dec. 8, l990, from a distance of almost 220,000 miles, while that on the left was
obtained at 9:35 a.m. PST Dec. 9, at a range of more than 350,000 miles. On the right, the near
side of the Moon and about 30 degrees of the far side (left edge) are visible. In the full disk on
the left, a little less than half the near side and more than half the far side (to the right) are
visible. The color composites used images taken through the violet and two near infrared filters.
The visualizations depict spectral properties of the lunar surface known from analysis of returned
samples to be related to composition or weathering of surface materials. The greenish-blue
region at the upper right in the full disk and the upper part of the right hand picture is Oceanus
Procellarum. The deeper blue mare regions here and elsewhere are relatively rich in titanium,
while the greens, yellows and light oranges indicate basalts low in titanium but rich in iron and
magnesium. The reds (deep orange in the right hand picture) are typically cratered highlands
relatively poor in titanium, iron and magnesium. In the full disk picture on the left, the yellowish
area to the south is part of the newly confirmed South Pole Aitken basin, a large circular
depression some 1,200 miles across, perhaps rich in iron and magnesium. Analysis of Apollo
lunar samples provided the basis for calibration of this spectral map; Galileo data, in turn, permit
broad extrapolation of the Apollo based composition information, reaching ultimately to the far
side of the Moon.
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