The NASA team is now saying they have proved that they could not have been produced by the blast itself.
美国国家航空和宇宙航行局的研究小组现在表示，他们已经证明，它们不可能是由爆炸本身产生的。
But the Nasa team is now saying they have proved that they could not have been produced by the blast itself.
但是如今美国宇航局研究团队表示，他们已经证明这些细菌不是爆炸本身造成的。
This is because the tremendous heat produced from a nuclear blast causes an up-draft of air that forms the familiar mushroom cloud.
这是因为核爆产生的大量的热能会把空气往上吸入，形成令人熟知的蘑菇云状。
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