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The Memnonia quadrangle is one of a series of 30 quadrangle maps of Mars used by the United States Geological Survey (USGS) Astrogeology Research Program. The Memnonia quadrangle is also referred to as MC-16 (Mars Chart-16).〔Davies, M.E.; Batson, R.M.; Wu, S.S.C. "Geodesy and Cartography" in Kieffer, H.H.; Jakosky, B.M.; Snyder, C.W.; Matthews, M.S., Eds. ''Mars.'' University of Arizona Press: Tucson, 1992.〕 The quadrangle is a region of Mars that covers latitude -30° to 0° and longitude 135° to 180°.〔(USGS Astrogeology: Planetary Map Listing )〕 The western part of Memnonia is a highly cratered highland region that exhibits a large range of crater degradation. Memnonia includes these topographical regions of Mars: * Arcadia Planitia * Amazonis Planitia * Lucus Planum * Terra Sirenum * Daedalia Planum * Terra Cimmeria Recently, evidence of water was found in the area. Layered sedimentary rocks were found in the wall and floor of Columbus Crater. These rocks could have been deposited by water or by wind. Hydrated minerals were found in some of the layers, so water may have been involved. Many ancient river valleys Vallis including Mangala Vallis, have been found in the Memnonia quadrangle. Mangala appears to have begun with the formation of a graben, a set of faults that may have exposed an aquifer. Dark slope streaks and troughts (fossae) are present in this quadrangle. Part of the Medusae Fossae Formation is found in the Memnonia quadrangle. == Layers == Columbus Crater contains layers, also called strata. Many places on Mars show rocks arranged in layers. Sometimes the layers are of different colors. Light-toned rocks on Mars have been associated with hydrated minerals like sulfates. The Mars Rover Opportunity examined such layers close-up with several instruments. Some layers are probably made up of fine particles because they seem to break up into find dust. Other layers break up into large boulders so they are probably much harder. Basalt, a volcanic rock, is thought to in the layers that form boulders. Basalt has been identified on Mars in many places. Instruments on orbiting spacecraft have detected clay (also called phyllosilicate) in some layers. Recent research with an orbiting near-infrared spectrometer, which reveals the types of minerals present based on the wavelengths of light they absorb, found evidence of layers of both clay and sulfates in Columbus crater.〔Cabrol, N. and E. Grin (eds.). 2010. Lakes on Mars. Elsevier.NY.〕 This is exactly what would appear if a large lake had slowly evaporated.〔Wray, J. et al. 2009. Columbus Crater and other possible plaelakes in Terra Sirenum, Mars. Lunar and Planetary Science Conference. 40: 1896.〕 Moreover, because some layers contained gypsum, a sulfate which forms in relatively fresh water, life could have formed in the crater. Scientists are excited about finding hydrated minerals such as sulfates and clays on Mars because they are usually formed in the presence of water. Places that contain clays and/or other hydrated minerals would be good places to look for evidence of life. Rock can form layers in a variety of ways. Volcanoes, wind, or water can produce layers. Image:Columbus Crater Layers.JPG|Columbus Crater Layers, as seen by HiRISE. This false-color image is about 800 feet across. Some of the layers contain hydrated minerals such as clay and sulfates. Image:Layers in Monument Valley.jpg|Layers in Monument Valley. These are accepted as being formed, at least in part, by water deposition. Since Mars contains similar layers, water remains as a major cause of layering on Mars. ESP 035848 1510memnoniacraterlayers.jpg|Layers in crater wall, as seen by HiRISE under HiWish program ESP 039673 1705layeredbuttes.jpg|Layers exposed at the base of a group of buttes in Mangala Valles in Memnonia quadrangle, as seen by HiRISE under HiWish program. Arrows point to boulders sitting in pits. The pits may have formed by winds, heat from the boulders melting ground ice, or some other process. 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「Memnonia quadrangle」の詳細全文を読む スポンサード リンク
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