小的危险是这种垃圾会打到人身上，少量碎片还会重新进入大气层。
There is a small risk that this rubbish will smack into human beings when minor amounts of it re-enter the earth's atmosphere.
火星上的 大气层很稀薄，只含有少量的氧； 而金星上的 大气层，则 是由我们几乎无法呼吸的气体构成的。
The atmosphere on Mars is very thin and contains very little oxygen, while that of Venus is made up of gases which we could not possibly breathe.
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