- Original Caption Released with Image:
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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, 1990, 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 nearside 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 nearside 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.
- Image Credit:
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NASA/JPL
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