bolide

NASA asteroid expert Don Yeomans, head of the agency's Near-Earth Object Program Office, told SPACE.com that the object which exploded over a thinly inhabited stretch of eastern Europe today was most likely an exploding fireball known as a bolide.

美国宇航局小行星专家、近地天体项目办公室负责人唐-耶麦斯告诉SPACE.com网站，在人烟稀少的远东地区上空爆炸的这颗天体很有可能是一颗火球，也称为火流星。

More and more evidences show that the volcanism might be the most likely cause of this event, although others triggers, such as sea level change, oceanic anoxia, bolide impact, methane gas hydrates, have not been excluded.

越来越多的证据显示火山作用是引起这次生物集群绝灭最可能的原因，虽然其他的因素，如海平面变化，海洋缺氧，地外行星撞击，甲烷及其水合物释放等，还没有排除。

Yeoman stressed that the bolide event was likely not associated at all with the incoming asteroid 2012 DA14, which will fly within 17200 miles ( 27000 kilometers) of Earth when it passes safely by our planet today.

耶麦斯强调说，这起火流星爆炸事件与即将掠过地球的小行星2012DA14没有任何关系、小行星2012DA14会安全地近距离掠过地球，与地球的距离不超过1.72英里（2.7千米）。

Magma activity and bolide effect are also announced accounting for the occurrence of PETM.

此外还有科学家用岩浆作用和地外星体撞击来解释PETM的发生.