英语听力 学英语,练听力,上听力课堂! 注册 登录
> 在线听力 > 英语高级听力 > 探索世界之火星生命 >  第5课

探索世界之火星生命 Horizon - Life On Mars 5

所属教程:探索世界之火星生命

浏览:

gewei

手机版
扫描二维码方便学习和分享
https://online2.tingclass.net/lesson/shi0529/0008/8433/5.mp3
http://image.tingclass.net/statics/js/2012

William Boynton is professor of planetary sciences at the University of Arizona. And he's dedicated his life to looking for water on Mars.

The link between life and water is very strong. Even here in the desert, there's life all around us. Now when looking for life on Mars, we use our basis of knowledge on Earth. And on Earth we know life requires water. So on Mars, we're gonna be looking for the places where we can find water.

Just like the desert, Mars may look dry but there are signs of water there. It's been known for almost a century that there are icecaps at the Martian poles.

When we look up at Mars, we see a dry, dusty planet. It doesn't look like a place for life. But there's tiny amounts of water in the atmosphere. And we know there are ice concentrations in the poles. So we're actually very optimistic that because there is at least, a speck of water on Mars, there might be a speck of life.

However, while the poles contain water ice, temperatures there can reach a staggering minus 150 degrees centigrade which meant these were not good places to search for life.

The conditions there are way too extreme. It's really just too cold. We really need liquid water for life. What we want to find on Mars is some place where we can find water in the more temperate regions. What we ultimately need to find is liquid water.

But the first indications were that if life needed liquid water, then Mars was out of luck. Conditions all over the planet seemed too cold, there appeared to be no prospect of water anywhere. These photographs changed everything. Taken by the Viking Space Probe in 1976, they showed what looked like dried-up river valleys.

You can see one here. You can see there's a, a valley through here, you can see it branches, the tributaries. Here's one branch going off here with tributaries. So this looks very much like, er, a terrestrial river system.

If these were dried-up riverbeds, it meant that Mars must once have had the perfect conditions for life.

ice concentration: the ratio expressed in tenths describing the area of the water surface covered by ice as a fraction of the whole area

内容来自 听力课堂网:http://www.tingclass.net/show-8433-237129-1.html
用手机学英语,请加听力课堂微信公众号:tingclass123
用户搜索

疯狂英语 英语语法 新概念英语 走遍美国 四级听力 英语音标 英语入门 发音 美语 四级 新东方 七年级 赖世雄 zero是什么意思

  • 频道推荐
  • |
  • 全站推荐
  • 广播听力
  • |
  • 推荐下载
  • 网站推荐