A Well-Preserved Meteor Impact
by Sarah Reed 胡德良 译
At only 16 meters deep and 45 meters wide, you wouldn't call the Kamil Crater in the southwest corner of Egypt "Deep Impact". Indeed, there are much more massive and impressive meteor craters scarring the Earth. Yet this small but perfectly preserved depression, discovered in 2009 during a Google Earth survey, is a rare beauty. There are currently 176 known craters on Earth's surface, of which only 15 are less than 300 meters wide—but all of these small craters have rapidly eroded and lost most of their original features. The Kamil Crater, however, has been well preserved, with the radial streaks of ejecta thrown out during impact still visible. And that's giving scientists a unique opportunity to study the characteristics of small-scale meteor impacts, researchers report online today in Science. The crater is in such pristine condition because it is geologically young (current estimates put the age at less than 5000 years) and because it escaped significant weathering, as it formed when extremely arid conditions were already prevalent in this remote part of Egypt. Craters like this one are typically found on planetary bodies in the Solar System that don't have atmospheres and therefore no weather systems to erode them. | 位于埃及西南角的卡米尔陨石坑只有16米深,口径45米,因此你不会称之为“深度撞击”。的确,地球上分布着许多更深更大的陨石坑。然而,这个保存完好的小型陨石坑有着独特的美,它是在2009年的谷歌地球探测中被发现的。目前,地球表面上拥有176个已知的陨石坑,其中只有15个陨石坑的口径小于300米,但是所有这些小型陨石坑很快都被风蚀掉,在很大程度上失去了原有的风貌,而卡米尔陨石坑保存完好,撞击时喷射出来的物质所形成的放射状条纹仍然清晰可见。研究人员在今天的《科学》杂志在线版上报道:该陨石坑为科学们提供了绝好的机会,使他们能够研究小规模陨石撞击的特点。该陨石坑保持着完好的原始状况,因为它从地质学上来讲尚属年轻(据目前推测它还不到5000年的历史),而且它没有受到重大的风蚀作用——它形成的时候异常干旱的状况已经流行于埃及的这一偏远地区。象这样的陨石坑通常存在于太阳系没有大气的行星上,因为在那里不受天气系统的侵蚀。 |
译自:美国《科学》杂志网站( July 22, 2010 2:00 PM)
原著:Sarah Reed
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