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The asteroid that hit the earth at the time of the dinosaur extinction was at least 10km diameter.
撞击地球导致恐龙灭绝的小行星直径至少是10公里。
The Permian mass extinction is even more severe,
二叠纪生物大灭绝更加严重，
so the asteroid that hit it that time must have been even larger, perhaps 15km in diameter.
所以当时撞上来的小行星应该更大，可能达到直径15公里。
It seemed the perfect answer.
这种解释看起来很完美。
A meteor the size of Manhattan had wiped out most of life on earth.
一颗大小如同曼哈顿的陨星消灭了地球上绝大多数生物。
Yet something didn't add up.
然而这还是有些说不通。
Nothing that size could hit the earth and not leave a trace.
但凡撞击地球的天体都不可能不留痕迹。
The meteor that had wiped out the dinosaurs had left a giant fingerprint in the shape of a crater,
消灭恐龙的那颗陨星在墨西哥海岸留下了一个陨石坑伤疤，
just off the coast of Mexico, where was the Permian crater.
那么二叠纪撞击坑又在何处呢。
No matter where they looked, nobody could find anything dating from the Permian era,
科学家们四处搜索，但无论如何也找不到符合二叠纪天体碰撞事件的陨石坑，
but then a scientist from London came up with a totally new idea.
后来一位来自伦敦的科学家提出了全新的观点。
Adrian Jones models the effects of impacts on the earth's crust.
Adrian Jones模拟了地壳撞击的结果。
He now suggested geologists were searching for the wrong thing.
他认为地质学家们是在寻找不存在的东西。
