High resolution LROC image of floor of the Apollo Basin, a large (538 km diameter) double-ringed impact crater in the southern hemisphere of the far side. This image shows part of the boundary between two flow units within the volcanic mare deposits on the crater's floor. The sharp boundary between the topographically higher lavas on the right side of the image and the lower ones on the left reveals layers, suggesting that multiple volcanic events were involved in forming some of the isolated volcanic plateaus seen within the otherwise uniform crater floor lava flows. Both the high and low materials here are heavily covered in impact craters, indicating that these lavas, like much of the Moon's surface, are ancient. Many boulders can also be seen shedding out of the upper layers and eroding down onto the lower deposits. Image is 880 meters wide, and north is up. Part of NAC frame M114953774LE. Credit: NASA/Goddard/Arizona State University
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d> WAC mosaic showing most of Apollo Basin's northern, southern, and western inner ring as well as the central floor's dark mare basalt deposits. The white arrow shows the location of the high-resolution NAC image discussed above. The white "X", near the boundary of the smooth, dark floor deposits and the rougher, brighter inner ring highlands materials, is the center of one of the 50 exploration regions of interest. The large (~51 km) crater at upper left is named Dryden; the largest (~49 km) crater partially visible just to the left of center at the bottom of the mosaic is called Chaffee. North is up and the width of mosaic is 130 km. Credit: NASA/Goddard/Arizona State University
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Unlike features on the nearside, craters and other landforms on the Moon's farside were only discovered beginning with the advent of the space age. Thus, many features have names that reflect more modern historical figures, places, and themes. One such example is the Apollo impact basin, a 538-km wide double-ringed impact crater in the southern hemisphere of the lunar farside, near 36°S, 152°W. This large feature was named in honor of the Apollo lunar explorationprogram, the series of NASA missions from 1968 through 1972 that culminated in twelve astronauts landing on the Moon, conducting scientific experiments, and returning more than 380 kg of lunar samples to the Earth. Many individual craters within the Apollo Basin are named after deceased NASA astronauts and officials, including, most recently, seven craters named after the fallen crew of the Space Shuttle Columbia. Apollo crater is an outstanding example of a concentric, double-ring impact structure, transitional in size between smaller simple bowl-shaped and complex central peak or peak-ring craters and larger impact basins like Orientale. It is actually superimposed on (and thus is younger than) the enormous South Pole-Aitken Basin, an impact structure (one of the largest in the Solar System) that dominates the Farside southern hemisphere. Apollo crater was selected as one of 50 sites for LRO to investigate in great detail for future exploration of the Moon. The specific study area (centered on the white "X" in the WAC context image above) was chosen because of the presence of relatively rare farside mare deposits in close association with the bright, presumably anorthositic highlands materials of the basin's inner ring of mountains. It is possible that because the crater formed on the rim of the South Pole-Aitken Basin, some of the materials excavated and/or uplifted by the Apollo crater impact event may have originated at great depths, perhaps even down to the lunar mantle.
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