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Keeler is a large lunar crater that lies on the Moon's far side. It is connected along the eastern edge to Heaviside, a walled plain of similar dimensions. Keeler, however, is the younger of the two formations, with more clearly delineated features. To the northeast of Keeler is the smaller crater Stratton, and to the northwest lies Ventris. The outer rim of Keeler is roughly circular, with a straight segment where it is joined to Heaviside. The northern portion of the rim is more irregular, with an outward protuberance to the north-northwest. Portions of the inner wall have a terrace structure, especially along the southern half. Within the crater interior, Planté lies on the eastern floor, adjacent to the inner wall. There is an interior ridge that runs from about the midpoint toward the west-southwest. The floor is generally level, with some areas of irregularity to the south. A few small and tiny craterlets mark the interior plain. Measurements with the electron reflectometer instrument on board the Lunar Prospector showed that this crater is one of a number of impact sites that show demagnetization. The low magnetic reading lies at the center of this crater, and the reduced field extends outward to about one and a half crater diameters. Scientists believe that shock demagnitization is the cause. Prior to naming, Keeler was called ''Crater 302'' by the IAU.〔Lunar Landmark Locations - Apollo 8, 10, 11, and 12 Missions. NASA technical note D-6082. Manned Spacecraft Center, Houston, Texas. November 1970. Figure 4.〕 ==Satellite craters== By convention these features are identified on lunar maps by placing the letter on the side of the crater midpoint that is closest to Keeler. Keeler S crater as08-17-2709hr.jpg|Keeler S crater photographed by Apollo 8 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Keeler (lunar crater)」の詳細全文を読む スポンサード リンク
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