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Adirondack is the nickname for Mars Exploration Rover Spirit's first target rock. Scientists chose Adirondack to be Spirit's first target rock after considering another, called ''Sashimi'', that would have been a shorter, straight-ahead drive. Spirit traversed the sandy martian terrain at Gusev Crater to arrive in front of this football-sized rock on January 18, 2004, just three days after it successfully rolled off the lander. Scientists named the angular rock after the Adirondack mountain range in New York. The name "Adirondacks" is an Anglicized version of the Mohawk ''ratirontaks'', meaning "they eat trees", a derogatory name which the Mohawk historically applied to the Algonquian-speaking tribes of the Adirondack Mountains; when food was scarce, the Algonquians would eat the buds and bark of trees.〔Donaldson, Alfred L., ''A History of the Adirondacks'', New York: Century, 1921. ISBN 0935796762 (reprint), pp. 34-35〕 The rock was selected as Spirit's first target because its dust-free, flat surface is ideally suited for grinding. Clean surfaces also are better for examining a rock's top coating. Spirit has also returned microscopic images and Mössbauer spectrometer readings of Adirondack taken the day before the rover developed computer and communication problems on January 22, 2004. Both are unprecedented investigations of any rock on another planet. The microscopic images indicate Adirondack is a hard, crystalline rock. The peaks large and small in Adirondack's electromagnetic spectrum reveal that the minerals in the rock include olivine, pyroxene and magnetite - a common composition in volcanic basalt rocks on Earth. Adirondack turned out to be typical of the other rocks on the plains. Spirit Rover's instruments determined that Adironack and other rocks of the plains contain the minerals pyroxene, olivine, plagioclase, and magnetite. These rocks can be classified in different ways. The amounts and types of minerals make the rocks primitive basalts—also called picritic basalts. The rocks are similar to ancient terrestrial rocks called basaltic komatiites. Rocks of the plains also resemble the basaltic shergottites, meteorites which came from Mars. One classification system compares the amount of alkali elements to the amount of silica on a graph; in this system, Gusev plains rocks lie near the junction of basalt, picrobasalt, and tephite. The Irvine-Barager classification calls them basalts.〔 McSween, etal. 2004. Basaltic Rocks Analyzed by the Spirit Rover in Gusev Crater. Science : 305. 842-845〕 Adirondack has been very slightly altered, probably by thin films of water because they are softer and contain veins of light colored material that may be bromine compounds, as well as coatings or rinds. It is thought that small amounts of water may have gotten into cracks inducing mineralization processes.〔McSween, etal. 2004. Basaltic Rocks Analyzed by the Spirit Rover in Gusev Crater. Science : 305. 842-845〕〔Arvidson, R. E., et al. (2004) Science, 305, 821-824〕 Coatings on the rocks in the plains may have occurred when rocks were buried and interacted with thin films of water and dust. One sign that they were altered was that it was easier to grind these rocks compared to the same types of rocks found on Earth. == See also == * Aeolis quadrangle * Composition of Mars * List of rocks on Mars * Scientific information from the Mars Exploration Rover mission 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「Adirondack (Mars)」の詳細全文を読む スポンサード リンク
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