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Mission to Mars Will Search for Lost Atmosphere

探索火星的任務將是尋找消失的大氣

The clues are adding up to give a picture of a distant Martian past, when the planet had a thick atmosphere that was warm enough for water to stream on the surface. But now the water’s gone, and the atmosphere is so thin that any water would boil away.

諸多線索綜合起來為我們描繪出一幅畫面：那是火星遙遠的過去，那時的火星還有著一層厚厚的大氣層，令這顆星球溫熱暖和，從而使水能夠在火星表面流淌。但如今，地表的水消失不見，而大氣層變得如此之薄，任何水分都會蒸發(fā)掉。

In fact, the vestigial atmosphere is still slowly dissipating into space. Why? Well, researchers believe that solar wind and radiation is behind the theft, and they’re planning a mission to find out, called MAVEN: Mars Atmosphere and Volatile Evolution Mission

事實上，殘余的大氣層仍在緩慢地消散于太空中。為什么呢？唔，研究人員認為太陽風和輻射是“幕后黑手”，他們打算開展一項任務來找出原因何在。這項任務名為MAVEN——火星大氣與揮發(fā)物演化任務（Mars Atmosphere and Volatile Evolution Mission）。

The solar wind is a stream of electrically-charged particles. It continuously flows from the sun out into space. We on Earth have protection in the form of a magnetic shield. But that shield is dead on Mars, gone for billions of years.

太陽風是一股帶點粒子流。它由太陽不斷發(fā)出，流入太空中。我們在地球上受到磁場屏蔽的保護，而火星的電磁場早在億萬年前就已經消失了。

Instead, the solar wind and the sun’s UV radiation give an electric charge to atoms and particles in Mars outer atmosphere. Then electric fields generated by the solar wind sweep away the charged particles. So the atmosphere becomes even thinner.

這樣，太陽風和太陽的紫外輻射賦予火星外層大氣中的原子和粒子一個電荷，然后由太陽風產生的電場將帶電粒子一掃而空。因此，火星的大氣層變得越來越薄。

Maven is scheduled to reach the red planet in 2014. Which will allow researchers to measure how much water and atmosphere are gone with the solar wind.

預計Maven將于2014年抵達這顆紅色星球。屆時，研究人員將能測出究竟有多少水和大氣隨太陽風而逝。

—Cynthia Graber

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