Other planets in our solar system lack the oxygenatmosphere that helps explain why life exists on Earth.
我们太阳系的其他行星缺乏氧气大气层，这有助于解释为什么地球上存在生命。
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The absence of an oxygenatmosphere on Mars and other planets in our solar system means that these planets also lack an ozone shield that would protect surface-dwelling life from UV radiation.