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SSS 2010-10-07

时间:2010-11-04 03:58来源:互联网 提供网友:ob8617   字体: [ ]
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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.

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 Volatile1 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.

 

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.

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.

Thanks for the minute, for Scientific American’s 60-Second Science. I’m Cynthia Graber.
 


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1 volatile tLQzQ     
adj.反复无常的,挥发性的,稍纵即逝的,脾气火爆的;n.挥发性物质
参考例句:
  • With the markets being so volatile,investments are at great risk.由于市场那么变化不定,投资冒着很大的风险。
  • His character was weak and volatile.他这个人意志薄弱,喜怒无常。
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