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The Medusae Fossae Formation is a large geological unit of uncertain origin on the planet Mars.〔(【引用サイトリンク】url=http://www.esa.int/Our_Activities/Space_Science/Mars_Express/The_Medusa_Fossae_formation_on_Mars/(print) )〕 It is named for the Medusa of Greek mythology. "Fossae" is Latin for "trenches". Located roughly at , it straddles the highland - lowland boundary near the Tharsis and Elysium volcanic areas. The Medusae Fossae Formation lies partly in five quadrangles: the Amazonis quadrangle, the Tharsis quadrangle, the Memnonia quadrangle, the Elysium quadrangle, and the Aeolis quadrangle. The Medusae Fossae Formation is a soft, easily eroded deposit that extends for nearly 1,000 km along the equator of Mars. Sometimes, the formation appears as a smooth and gently undulating surface, however in places it is wind-sculpted into ridges and grooves.〔 Radar imaging has suggested that the region may contain either extremely porous rock (for example volcanic ash) or deep layers of glacier-like ice deposits amounting to about the same quantity as is stored in Mars' south polar cap. Using a global climate model, a group of researchers headed by Laura Kerber found that the Medusae Fossae Formation could have been formed from ash from the volcanoes Apollinaris Mons, Arsia Mons, and possibly Pavonis Mons.〔Kerber L., et al. 2012. The disporsal of pyroclasts from ancient explosive volcanoes on Mars: Implications for the friable layered deposits. Icarus. 219:358-381.〕 Further evidence for a fine-grained composition is the fact that the area gives almost no radar return. For this reason it has been called a "stealth" region. The formation is divided into three subunits (members) that are all considered to be of Amazonian age, the youngest era in martian geological history. Image:Medusae Fossae Remnant.jpg|Plateau made up of Medusae Fossae materials and rootless cones, as seen by HiRISE. Rootless cones are caused by lava interacting with water ice. Wakes are caused by lava flowing over a source of steam. ESP 036510 1735layers.jpg|Mounds with layers, as seen by HiRISE under HiWish program Location is East of Gale Crater in the Aeolis quadrangle. Wikiesp036510 1735layersmedussa.jpg|Layers and mounds in Medusae Fossae Formation, as seen by HiRISE under HiWish program Location is East of Gale Crater in the Aeolis quadrangle. Wikiesp036510 1735moundsmedussa.jpg|Layers and a field of small mounds Medusae Fossae Formation, as seen by HiRISE under HiWish program Location is East of Gale Crater in the Aeolis quadrangle. Wikiesp036510 1735layersmound.jpg|Mound showing layers at the base, as seen by HiRISE under HiWish program Location is East of Gale Crater in the Aeolis quadrangle. Image:Medusae Formation Layers.jpg|Layers in lower member of Medusae Fossae Formation, as seen by HiRISE. Location is East of Gale Crater in the Aeolis quadrangle. ESP 038302 1735medusaelayers.jpg|Surface features along a scarp in Medusae Fossae formation, as seen by HiRISE under HiWish program Location is Memnonia quadrangle. ==Inverted relief== The lower portion (member) of Medusae Fossae Formation contains many patterns and shapes that are thought to be the remains of streams. It is believed that streams formed valleys that were filled and became resistant to erosion by cementation of minerals or by the gathering of a coarse covering layer to form an inverted relief. These inverted stream beds are sometimes called sinuous ridges or raised curvilinear features. They have been divided into six classes: flat-crested, narrow-crested, round-crested, branching, non-branching, and multilevel. They may be a kilometer or so in length. Their height ranges from a meter to greater than 10 meters, while the width of the narrow ones is less than 10 meters.〔http://www.sciencedirect.com/science/journal/00191035〕 Image:Sinuous Ridges in Medusae Formation.jpg|Sinuous Ridges within a branching fan in lower member of Medusae Fossae Formation, as seen by HiRISE. Location is Aeolis quadrangle. 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「Medusae Fossae Formation」の詳細全文を読む スポンサード リンク
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