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Rahe is a crater on the planet Mars in the Tharsis quadrangle, positioned at 25.05° north latitude and 262.52° east longitude, between the volcanoes Ceraunius Tholus and Uranius Tholus. It is named after Jurgen H. Rahe, a German-American astronomer and NASA science program director.〔 The crater has an elongated shape measuring 35 km by 18 km and is the result of an oblique impact. A channel connects Rahe crater to the vicinity of the summit caldera of Ceraunius Tholus, with an interesting fan-shaped deposit at the lower end. Rahe Crater is 1 km deep in places, and was created by a low angle impact which is evident by its elongated shape and ejecta deposit in the shape of a “butterfly.”〔Gault, D. J. Wedekind. 1978. Experimental studies of oblique impact. Proc. Lunar Planet. Sci. Conf. 9, 3843-3875.〕〔Nyquist, L. 1983. Do Oblique Impacts Produce Martian Meteorites? Proc. Lunar Planet. Sci. Conf. 13, pt.2 Geophys. Res. (Supp.) 88S, A785-A798.〕 Rahe Crater is believed to once have held a lake. The lake was formed because heat from the nearby volcano Ceraunius Tholus melted glaciers. Melt water first collected in the caldera of Cerunius Tholus, and then spilled over the caldera rim forming a valley and the lake in Rahe Crater. The valley that carried the water was about 200 m wide. A delta formed where the valley entered Rahe Crater.〔Fassett, C. J. Head. 2007. Valley Formation on Martian Volcanoes in the Hesperian: Evidence for Melting of Summit Snowpack, Caldera Lake Formation, Drainage and Erosion on Ceraunis Tholus, Mars. Icarus: 189, 118-135.〕 This type of event involving volcanic heat melting glaciers is common in Iceland. Eruptions under glaciers are called jökulhlaups and average two each century.〔Bjornnson, H, F. Palsson, M. Gudmundsson. 2000. Surface and bedrock topography of the Myrdalsjokull ice cap, Iceland: The Katla caldera, eruption sites and routes of jökulhlaups. Jokull: 49, 29-46.〕 Studies of climate change show that many low-latitude regions accumulated large amounts of snow when the climate was different.〔Head, J. et al. 2005. Tropical to mid-latitude snow and ice accumulation, flor and glaciation on Mars. Nature:434,346-351.〕〔Head, J. et al. 2006. Extensive valley glacier deposits in the northern mid-latitudes of Mars: Evidence for Late Amazonian obliquity-driven climate change. Earth Planet. Sci. Lett. 241,663-671.〕 Wikirahe.jpg|Rahe Crater, as seen by CTX camera (on Mars Reconnaissance Orbiter). Wikirahedelta.jpg|Delta in Rahe Crater, as seen by CTX camera (on Mars Reconnaissance Orbiter). Note: this is an enlargement from the previous image of Rahe Crater. ==See also== * Climate of Mars * Geology of Mars * Impact crater * List of craters on Mars 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「Rahe (crater)」の詳細全文を読む スポンサード リンク
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