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Meteorite fall statistics are frequently used by planetary scientists to approximate the true flux of meteorites on the Earth. Meteorite falls are those meteorites that are collected soon after being witnessed to fall, whereas meteorite finds are discovered at a later time. Although there are 30x more finds than falls, their raw distribution of types does not accurately reflect what falls to Earth. The reasons for this include: #Some meteorite types are easier to find than others #Some meteorite types are degraded by weathering more quickly than others #Some meteorites, especially iron meteorites, may have been collected by people in the past who recognized them as being unusual and/or useful, thereby removing them from the scientific record #Many meteorites fall as showers of many stones, but when they are collected long after the event it may be difficult to tell which ones were part of the same fall #Many meteorites are found by people who sell meteorites... valuable, rare types become known to science quickly, while those of low value may never be described. There have been many attempts to correct statistical analyses of meteorite finds for some of these effects, especially to estimate the frequency with which rare meteorite types fall. For example, there are over 100 known lunar meteorite finds, but none has ever been observed to fall. However, for abundant types, meteorite fall statistics are generally preferred. These statistics are current through June 9, 2012. ==Statistics by material== For most meteorite falls, even those that occurred long ago or for which material has never received complete scientific characterization, it is known whether the object was a stone, stony iron, or iron meteorite. Here are the numbers and percentages of each type, based on literature data.〔(Meteoritical Bulletin Database )〕〔(The NHM Catalogue of Meteorites )〕〔(MetBase )〕 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「Meteorite fall statistics」の詳細全文を読む スポンサード リンク
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