The Galileo Project was originally conceived as a mission to study Jupiter and its satellites. Most early plans for this mission called for direct flights to Jupiter. After new constraints were placed on shuttle operations after the Challenger accident and the Centaur program was cancelled, a direct flight to Jupiter became impossible. A new flight plan was developed that involved flybys of Venus and Earth to provide “gravity assists” that would help the spacecraft on its way to Jupiter. Although this method greatly increased the time it would take Galileo to arrive at Jupiter, it did provide opportunities for the spacecraft to pass by and examine several other bodies. The new flight path included two flybys of Earth, during which Galileo was able to obtain a number of photographs of the Moon.
This color image of the Moon was taken by Galileo at 9:35 a.m. PST, December 9, 1990, at a range of about 350,000 miles. The color composite uses monochrome images taken through violet, red, and near-infrared filters. The concentric, circular Orientale Basin, 600 miles across, is near the center, the nearside is to the right, and the farside to the left. At the upper right is the large, dark Oceanus Procellarum; below it is the smaller Mare Humorum. These, like the small, dark Mare Orientale in the center of the basin, formed more than 3 billion years ago as basaltic lava flows. At the lower left, among the southern cratered highlands of the farside, is the South-Pole-Aitken Basin, similar to Orientale but twice as large in diameter and much older and more degraded by cratering and weathering. The cratered highlands of the near- and farsides and the Maria are covered with scattered bright, young ray craters. JPL image P-37329.
This false-color mosaic was constructed from a series of 53 images taken through three spectral filters by Galileo’s imaging system as the spacecraft flew over the northern regions of the Moon on December 7, 1992. The part of the Moon visible from Earth is on the left side in this view. The color mosaic shows compositional variations in parts of the Moon’s northern hemisphere. Bright pinkish areas are highlands materials, such as those surrounding the oval lava-filled Crisium impact basin toward the bottom of the picture. Blue to orange shades indicate volcanic lava flows. To the left of Crisium, the dark blue Mare Tranquillitatis is richer in titanium than the green and orange maria above it. Thin mineral-rich soils associated with relatively recent impacts are represented by light blue colors; the youngest craters have prominent blue rays extending from them. (JPL image P-41490).
This false-color image of part of the Moon was constructed from four images taken by Galileo’s imaging system as the spacecraft flew past the Moon on December 7, 1992. The images were processed to exaggerate the colors of the lunar surface for analytical purposes. Titanium-rich soils, typical of the Apollo 11 landing site, appear blue, as seen in Mare Tranquillitatis (left side); soils lower in titanium appear orange, as seen in Mare Serenitatis (lower right). Dark purple patches (left center) mark the Apollo 17 landing site and are ancient explosive volcanic deposits. Most of the lunar hiqhlands appear red, indicating their low titanium and iron content. (JPL image P-41477.)
While Galileo observations of the Moon were brief, its instruments were still able to gather useful information. Galileo obtained information in new areas and with new instruments that helped clarify information gathered by other missions to the Moon. It provided clearer views of the lunar farside and the north and south polar regions. The multispectral information provided by Galileo’s instruments was of particular interest.
More Galileo Mission Information at Other Sites
- Galileo Mission Information at NSSDC
- Galileo Mission Information at JPL/NASA
- More on Galileo Lunar Flybys at NSSDC