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你是火星人吗?

(2011-10-02 00:33:27)
标签:

杂谈

火星

分类: Digest

Are You A Martian

你是火星人吗

    我们都是火星人吗?根据很多行星科学家的说法,我们可以想象地球上所有的生命来自起源于火星的生物,然后通过小行星带到地球。现在由麻省理工学院和哈佛大学研究者联合研制的一种仪器,能在未来验证这一猜想。

In order to detect(探测)signs of past or present life on Mars — if it is in fact true that we're related — then a promising strategy would be to search for DNA or RNA, and specifically for particular sequences(序列)of these molecules that are nearly universal in all forms of terrestrial(地球上的)life. That's the strategy being pursued by MIT and Harvard researchers.

The idea is based on several facts that have now been well established. First, in the early days of the solar system, the climates on Mars and the Earth were much more similar than they are now, so life that took hold on one planet could presumably have survived on the other. Second, an estimated one billion tons of rock have traveled from Mars to Earth, blasted loose by asteroid(小行星)impacts and then traveling through interplanetary space(行星际空间)before striking Earth's surface. Third, microbes(微生物)have been shown to be capable of surviving the initial(初期的)shock of such an impact, and there is some evidence they could also survive the thousands of years of transit(运载)through space before arriving at another planet.

So the various steps needed for life to have started on one planet and spread to another are all plausible(可信的). Additionally, orbital dynamics show that it's about 100 times easier for rocks to travel from Mars to Earth than the other way. So if life got started there first, microbes could have been carried here and we might all be its descendants(后代).

你是火星人吗?

If we are descendants from Mars, there might be important lessons to be learned about our own biological origins by studying biochemistry on our neighbor planet, where biological traces erased(消除)long ago here on Earthmight have been preserved in the Martian deep freeze.

The MIT researchers' device would take samples of Martian soil and isolate any living microbes that might be present, or microbial remnants (which can be preserved for about up to a million years and still contain viable DNA), and separate out the genetic material in order to use standard biochemical techniques to analyze their genetic sequences.

Even a few years ago, that might have seemed like more of a long shot, but recent Mars orbiter and rover missions have clearly shown that Mars once had abundant water, and many of the conditions thought to be needed to support life. And although the surface of Mars today is too cold and dry to support known life forms, there is evidence that liquid water may exist not far below the surface.

So the team has been developing a device that could take a sample of Martian soil from below the surface — perhaps dredged up by a rover equipped with a deep drill — and process it to separate out any possible organisms, amplify their DNA or RNA using the same techniques used for forensic(法医的)DNA testing same techniques used for forensic(法医的)DNA testing on Earth, and then use biochemical markers to search for signs of particular, genetic sequences that are nearly universal among all known life forms. The researchers estimate that it could take two more years to complete the design and testing of a prototype SETG device. Although the proposed device has not yet been selected for any upcoming Mars mission, a future mission with a lander or rover equipped with a drill could potentially carry this life-detection instrument.

你是火星人吗?

No instrument has been sent to Mars specifically to look for evidence of life since NASA's twin Viking landers in 1976, which produced tantalizing(诱人的)but ambiguous(模糊的)results. An instrument on the Mars Science Lander to be launched in the fall will investigate chemistry relevant to life. The instrument from the MIT-Harvard team directly addresses Earth-like molecular biology.    


Source: http://web.mit.edu/


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