Mars has an insubstantial atmosphere, consisting almost entirely of carbon dioxide.

火星周围有一个薄薄的大气层，几乎全由二氧化碳构成。

《柯林斯英汉双解大词典》

The atmosphere of Mars could not support life.

生命无法在火星的大气环境下生存。

《牛津词典》

The absence of an oxygen atmosphere 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.

在火星和我们太阳系的其他行星上没有氧气，这意味着这些行星也缺乏保护地表生物免受紫外线辐射的臭氧层。

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As part of our commitment to maintain American leadership in the exploration of Mars beyond the Curiosity mission, NASA will launch the Mars Atmosphere and Volatile EvolutioN (MAVEN) orbiter next year.

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In fact, when mission managers in the control room at the Jet Propulsion Laboratory first get word early Monday that the craft has reached the top of the Mars atmosphere, the vehicle will have been safe or smashed on the surface for at least seven minutes.

WSJ: NASA's Robot Lab Curiosity Nears Mars

Overall, Mars' atmosphere reduces the radiation dose compared to what we saw during the flight to Mars.

ENGADGET: Curiosity rover finds radiation levels on Mars are safe for humans