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Tyrrhena Terra is a large area on Mars, centered south of the Martian equator and immediately northeast of the Hellas basin. Its coordinates are , and it covers 2300 km at its broadest extent. It was named for a classic albedo feature of the planet and is in the Mare Tyrrhenum quadrangle of Mars. Tyrrhena Terra is typical of the southern Martian terrae, with heavily cratered highlands and other rugged terrain. It contains the large volcano Tyrrhena Patera, one of the oldest volcanoes on Mars. 〔Hartmann, W. 2003. A Traveler's Guide to Mars. Workman Publishing. NY NY.〕 Its largest crater is Herschel. Licus Vallis and the Ausonia Montes are other major features in the region. Some channels and dunes are visible in Tyrrhena Terra, as shown in the images below. Wikiesp 035761 1520layers.jpg|Layers in a valley East of Terby Crater, as seen by HiRISE under HiWish program. Location is Iapygia quadrangle. Wikiterracimmeriaboundaries.jpg|MOLA map showing boundaries of Tyrrhena Terra and other nearby regions Image:25897ausoniachannel.jpg|Channel in Ausonia Mensa, as seen by HiRISE under the HiWish program ESP 036051 1515iapyagiachannel.jpg|Channel within a larger channel, as seen by HiRISE under HiWish program Image:ESP 037844 1690dunes.jpg|Dunes in crater, as seen by HiRISE under HiWish program. Image:ESP 034956 1745dunescraters.jpg|Dunes among craters, as seen by HiRISE under HiWish program. Wikibriault.jpg|Briault Crater, as seen by CTX camera (on Mars Reconnaissance Orbiter). Wikibriaultdunes.jpg|Dunes on the floor of Briault Crater, as seen by CTX camera (on Mars Reconnaissance Orbiter). Note: this is an enlargement of the previous image of Briault Crater. ==Dunes== When there are perfect conditions for producing sand dunes, steady wind in one direction and just enough sand, a barchan sand dune forms. Barchans have a gentle slope on the wind side and a much steeper slope on the lee side where horns or a notch often forms. Some of the dunes in the pictures above are barchans. Barchan is a Russian term because this type of dune was first seen in the desert regions of Turkistan.〔http://www.britannica.com/EBchecked/topic/53068/barchan〕 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「Tyrrhena Terra」の詳細全文を読む スポンサード リンク
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