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諸多線索綜合起來為我們描繪出一幅畫面：那是火星遙遠(yuǎn)的過去，那時(shí)的火星還有著一層厚厚的大氣層，令這顆星球溫?zé)崤停瑥亩顾軌蛟诨鹦潜砻媪魈省５缃瘢乇淼乃Р灰姡髿鈱幼兊萌绱酥。魏嗡侄紩?huì)蒸發(fā)掉。
Arriving in 2014, the Mars Atmosphere and Volatile Evolution Mission (MAVEN) will see if the solar wind and radiation are behind the loss of the Martian atmosphere. Cynthia Graber reports
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 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.
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.
—Cynthia Graber
[The above text is an exact transcript of this podcast.]
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