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Several bright surface features (also known as faculae) were discovered on the dwarf planet Ceres by the ''Dawn'' spacecraft in 2015. The brightest cluster of spots ("Spot 5") is located in an crater called Occator. The largest and brightest component of the cluster is in the center of the crater, with dimmer spots located towards this crater's eastern rim. Early in the orbital phase of the ''Dawn'' mission, the high albedo of these spots was speculated to be due to some kind of outgassing,〔(LPSC 2015: First results from Dawn at Ceres: provisional place names and possible plumes )〕 and subsequent closer images helped scientists determine that it is material with a high level of reflection, and suggested ice and salt as possibilities. These bright features have an albedo of about 40%, four times brighter than the average of Ceres's surface.〔 〕 ==Spot 5== The brightest cluster of spots ("Spot 5") is located in an crater called Occator,〔〔 which is located at 19.86° N latitude; 238.85 E longitude.〔〔 Alan Duffy of Swinburne University suggested "a meteorite strike either shook covering material off the salty ice or heated it so that salty water rose to the surface as a geyser. The water escaped into space and now, only the salt remains."〔(A. Duffy – Cosmos – What on Ceres are those bright spots? )〕 A haze that fills around half of Occator crater and that does not extend over its rim〔Chris Russel at ()〕 periodically appears around Spot 5, the best known bright spot, adding credence to the idea that some sort of outgassing or volcanism is occurring.〔(Dawn at Ceres: A haze in Occator crater? Posted by Andrew Rivkin )〕 ''Dawns images led to widespread reports in the media about the bright spots, including in news sources, astronomy magazines, and science magazines. An informal NASA poll during May offered the following ideas for the nature of the spots: ice, volcanos, geysers, salt deposits, rock, or other. Asteroid specialist A. Rivkin noted, in an article by ''Sky & Telescope'' magazine, that at low angles a haze can be seen in but not outside of the crater, and speculated that this could be sublimated vapor from ice, possibly linked to the bright spots.〔(Sky and Telescope magazine - Dawn Sees Ceres Bright Spots and More By Emily Poore July 30, 2015 )〕 Reflectivity studies from September 2015 suggest that the spots are probably salts rather than ice, implying that Ceres's interior is somehow delivering fresh salt to the surface.〔(Ceres' Mysterious Bright Spots Aren't Made of Ice After All ). ''Gizmodo'', 1 October 2015〕 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「Bright spots on Ceres」の詳細全文を読む スポンサード リンク
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