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(6178) 1986 DA is a 2.3-kilometre-diameter M-type Mars-crosser and near-Earth asteroid, notable for being significantly more radar-reflective than other asteroids. It is an Amor asteroid, which means it approaches the orbit of Earth from the outside but does not cross it. Radar measurements suggest it is composed of nickel and iron and that it was derived from the center of a much larger object that experienced melting and differentiation. The observed radar albedo was 0.58 and the optical albedo was 0.14. This asteroid was most probably formed from a larger body through a catastrophic collision with another object. Radar measurements of this body indicate that the surface is relatively smooth on scales of less than a meter, but it is highly irregular on scales of 10–100 meters. The delta-v for a spacecraft rendezvous with this asteroid from low earth orbit is 7.1 km/s. 1986 DA reached perihelion in its orbit on March 6, 2005. Asteroid 1986 DA achieved its most notable recognition when scientists revealed that it contained over "10,000 tons of gold and 100,000 tons of platinum", or an approximate value at the time of its discovery of "$90 billion for the gold and a cool trillion dollars for the platinum, plus loose change for the asteroid's 10 billion tons of iron and a billion tons of nickel." In 2012 the estimated value of 100,000 tons of platinum was worth approximately five trillion US dollars. == References == 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「(6178) 1986 DA」の詳細全文を読む スポンサード リンク
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