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英海听涛

启用你的听觉,更自然地感受更辽阔的世界。——用进废退!

 
 
 

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喜欢科学,偏爱自然科学。也喜欢技术,儿时喜围观打锡壶的和锔盆锔锅的。当过工人,当过兵,第二故乡是湖南、广西和广东。

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火星消息要点  

2013-12-31 10:59:47|  分类: 科学与技术 |  标签: |举报 |字号 订阅

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NASA的‘好奇号’火星车于2012年八月在火星着陆,也就是去年。它在过去15个月里探索火星上一个称为盖尔陨坑的地方。本周操纵好奇号火星车的团队报告了到目前为止他们的发现。我们想你会乐意听到这新信息。下面是《速射科学》谈关于我们的行星邻居,由多米尼克-福特和汉娜-克里奇洛播送。

如今火星是一个荒芜和布满陨坑的世界,温度通常大大低于零下100摄氏度,冷得甚至足以使二氧化碳形成霜。

用肉眼仰望夜空,火星引人注目的发红。这是因为火星土壤散布着微粒状的氧化铁,也就是铁锈。

对于生存来说火星是个严酷的地方,低温并不是唯一的原因。它的大气浓度是地球大气的百分之一,而且主要由二氧化碳而不是由可呼吸的氧气构成。

尽管如此,吸引空间科学家的是古老的渠道,它们刻入火星表面,看上去像是干涸了的河床。

现在火星表面的压力太低,不足以使液体的水存在,所以这些渠道的存在意味着火星过去的大气浓度要高得多,其气候应当显著不同。

好奇号的目标之一就是要弄清楚这种气候变化是如何发生的。如果过去火星大气中存在着多得多的二氧化碳,我们不清楚这些碳去哪儿啦?

最有可能的回答是,它变成了富含碳的石灰岩。不过一个大谜团是为什么在火星上从没有发现过多少石灰岩呢?

好奇号火星车还测量了火星表面的放射性。没有稠密大气的保护,火星表面饱受太阳辐射的冲击。

好奇号的放射性测量数据显示,即使是地球上最顽强的生命类型也经受不住火星土壤所受到的辐射。

好奇号接下来的问题之一是微生物是否曾经在远古的火星上繁荣过,尽管现在不能。

空间科学家正在火星土壤中搜索基于碳的大分子,这些分子的复杂性决定了它们只能由古老的生命合成。

如果好奇号到2018年还不能发现证据,这种探索工作就将由欧洲ExoMars火星车接替,它将携带下一代更灵敏的仪器在那时登陆火星。

——《赤诚科学家播客》/《超级成形——我!》,英国 2013/12/17

NASA’s Curiosity rover landed on Mars in August 2012, just last year. It’s been there for the past fifteen months exploring a region of Mars called the Gail Crater. And this week the team who are running the rover reported on what they’ve found so far. So we thought you’d appreciate an update and here is your Quick Fire Science about our planetary next neighbor with Dominic Ford and with Hannah Critchlow.

Today Mars is a barren and cratered world where temperatures commonly dip well below minus a hundred degrees centigrade, cold enough for even carbon dioxide to form frost.

To the unaided eye and looking up at the night sky, Mars is strikingly red. This is because the Martian soil is littered with fine particles of iron oxide also called rust.

Low temperatures are not the only reason why Mars would be a harsh place to live. Its atmosphere is a hundred times thinner than the Earth’s, and is composed mainly of carbon dioxide rather than breathable oxygen.

What fascinates space scientists, though, is that ancient channels are carved into the Martian surface, which look like dried up riverbeds.

Today the pressure of Mars’ surface is too low for liquid water to exist, so the presence of channels implies that Mars weather was radically different in the past with a much thicker atmosphere.

One of the Curiosity rover’s aims is to work out how this change of climate happened. If there was once much more carbon dioxide gas in Mars’ atmosphere, it’s unclear, where that carbon could have hone.

The most likely answer is that it turned into carbon rich limestone. Yet a big mystery is why very little limestone has ever been found on Mars.

The Curiosity rover has also been measuring radiation on Mars’ surface. Without a thick atmosphere to protect it, Mars’ surface is blasted by the full brunt of radiation produced by the sun.

In fact, measurement in Curiosity’s radiation census suggests that even the hardiest lifeforms of the Earth could not withstand the irradiation the Martian soil receives.

One of the next questions for Curiosity is whether microbial life might have been able to thrive on Mars in the distant past, even if not today.

Space scientists are searching the Martian soil for large carbon-based molecules that are so complex that only ancient lifeforms could have assembled them.

If Curiosity doesn’t find any by two thousand and eighteen, the quest will then be taking up by the European ExoMars Rover, which will arrive carrying the next generation of even more sensitive instruments.

-- The Naked Scientists / Super-shape me! 2013/12/17

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