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寻找一个曾经蓝天白云 小河流水的火星【AGapp下载】

本文摘要:For lifeless chemical compounds to organize themselves into something alive, scientists generally agree, three sets of things must be present:科学家基本普遍认为,无生命的化学物质自行人组构成生命,必须不具备三个前提条件:■ Standing water and an energy source.■ 静态水和能量来源。

For lifeless chemical compounds to organize themselves into something alive, scientists generally agree, three sets of things must be present:科学家基本普遍认为,无生命的化学物质自行人组构成生命,必须不具备三个前提条件:■ Standing water and an energy source.■ 静态水和能量来源。■ Five basic elements: carbon, oxygen, hydrogen, phosphorus and nitrogen.■ 五种基本元素:碳、氧、氢、磷和氮。■ And time, lots of time.■ 还有时间,漫长的时间。

In its search for environments where life might have started on Mars, the Curiosity rover has found the standing water, the energy and the key elements with the right atomic charges. As a result, scientists have concluded that at least some of the planet must have been habitable long ago.在找寻火星上适合生命的环境的过程中,“奇怪号”火星探测车寻找了静态水、能源和原子电量正好适合的基本元素。据此,科学家得出结论,火星上最少有些地方在很久以前是适合生命不存在的。


But the period when all conditions were right was counted in hundreds to thousands of years, a very small opening by origin-of-life standards.但在火星历史上,所有这些条件都不具备的时间跨度约是几百到几千年,而以生命起源的标准取决于,那觉得不过是转瞬之间。That has now changed. John P. Grotzinger of Caltech, the project scientist for the mission, reported at a news conference on Monday that the rover’s yearlong trek to Mount Sharp provided strong new evidence that Gale Crater had large lakes, rivers and deltas, on and off, for millions to tens of millions of years. The geology shows that even when the surface water dried up, plenty of water would have remained underground, he said.不过,现在有了新发现。负责管理“奇怪号”火星项目的加州理工科学家约翰·P·格罗青格(John P. Grotzinger)周一(12月8日——学术著作)在新闻发布会上宣告,“奇怪号”向着夏普峰历时一年的长途跋涉找到了有力的新证据,证明盖尔环形山曾有大型湖泊、河流和三角洲,而且这些地貌断断续续不存在的时间有数百万到数千万年之间。他说道,未知的火星地理特征解释,即使是在地表水干枯的时候,也有地下水不存在。

Moreover, the team concluded, numerous deltalike and lakelike formations detected by orbiting satellites are almost certainly the dried remains of substantial ancient lakes and deltas. None of this proves that life existed on the planet, but the case for an early Mars that was ripe and ready for life has grown stronger.此外,科学家团队还得出结论,环绕着火星的卫星找到大量类三角洲或类湖泊地貌,完全可以认同就是古代湖泊和三角洲干枯之后的遗迹。这些皆无法证明火星上曾有生命,但早期火星适合生命不存在的可能性很大地强化了。

“As a science team, Mars is looking very attractive to us as a habitable planet,” Dr. Grotzinger said in an interview. “Not just sections of Gale Crater and not just a handful of locations, but at different times around the globe.”“对于我们科学团队来说,火星作为一个生命宜居行星,变得十分诱人,”格罗青格说道。“不仅是在盖尔环形山,也不仅是受限几个地点,而是在有所不同历史时期遍及火星各处。”And John M. Grunsfeld, a former astronaut who is NASA’s associate administrator for science, said that after almost 28 months on Mars, Curiosity has given scientists insight into how and where to look for clues of ancient life. “We don’t know if life ever started on Mars, but if it did, we now have a better chance of discovering it” on future missions, he said.美国国家航空航天局(NASA)科学副总监、前宇航员约翰·M·格伦斯菲尔德(John M. Grunsfeld)也说道,“奇怪号”在火星的将近28个月让科学家教给很多东西,告诉该怎样找寻古代生命的线索,以及到哪里去找。“我们不告诉火星上否曾有生命起源,但如果有的话,我们[在今后探寻任务中]找到它的机会更大了,”他说道。

Another missing piece of the story has been the inability to detect organic compounds — the carbon-based building blocks of life.探寻生命起源的过程中另一个缺陷的环节是仍然没寻找有机化合物——包含生命的碳基元件。That too may soon change. Last spring, several Curiosity team members reported the detection of some simple organics that appeared to be Martian. The findings were not definitive, but NASA has scheduled a news conference Dec. 14 at the annual meeting of the American Geophysical Union with “new information” about the search for organics. “Our original interpretation — that there was a good chance the organics we were seeing are Martian — hasn’t changed,” said Daniel P. Glavin of the Goddard Spaceflight Center, an author of the earlier paper. “This interpretation will be expanded on at A.G.U.”这一点也有可能迅速不会有突破。今年春季,“奇怪号”的几位科学家报告找到了有可能是火星上的某些非常简单有机物。


这个找到没遽下结论,但航天局早已决定了12月14日在美国地球物理学不会(American Geophysical Union)年会上开会新闻发布会,公布关于探寻火星有机物的“新的消息”。那篇论文的作者之一、戈达德航天中心(Goddard Spaceflight Center)的丹尼尔·P·格莱文(Daniel P. Glavin)说道:“我们最初的理解——很有可能我们找到的就是火星有机物——并没转变。在AGU年会上我们不会更进一步讲解。”Curiosity does not carry life-detection instruments, in large part because there is no consensus on what such an instrument might be. A finding of life based on what at first appeared to be metabolic activity, detected during the Viking missions of 1977, was so controversial that NASA ultimately rejected it. So scientists have been using a variety of tools — from geology and other earth sciences, organic and mineral chemistry, atmospheric measurements and sophisticated cameras — to determine whether life could have arisen and survived in Gale Crater and other locations with similar characteristics.“奇怪号”没配备生命观测设备,主要是因为到底该用什么样的设备,科学家没达成协议共识。


Another member of the Curiosity team, Roger Summons of M.I.T., says that findings from that rover and previous missions suggest that early Mars may have been quite similar to early Earth.“奇怪号”团队的另一名成员、麻省理工的罗杰·萨曼斯(Roger Summons)说道,“奇怪号”和历史上其他的火星探寻表明,早期火星也许和早期地球十分相似。For the first billion years, he said, both planets had stable environments that could support life for substantial periods, and both still share the same chemistry and processes for altering rocks. There is a general scientific consensus that life began on Earth some 3.8 billion years ago, and Dr. Summons said it was clear that the same could have happened on Mars. Or as Dr. Grunsfeld put it, “What I get excited about is imagining a Mars 3.5 to 4 billion years ago, a planet with a thick atmosphere, maybe a blue sky with puffy clouds and mountains and lakes and rivers.”他说道,最初的10亿年,两个星球都有平稳的环境,容许生命在非常宽的时间里不存在。直到今天,地球和火星依然有完全相同的化学包含以及促成岩石再次发生改变的地质过程。


”Many similarities disappeared after Mars, a much smaller planet, lost much of its protective atmosphere by the end of its first billion years. So searching for possible Martian life involves digging deep below the surface or detecting microbial remains billions of years old. Identifying ancient microbial life has proved extremely difficult and controversial on Earth, and the challenge on Mars is considerably greater.在它基本童年第一个10亿年的时候,火星这颗大得多的行星失去了大部分维护它的大气层,于是很多相似性也消失了。因此,搜索火星生命就必须深深地挖出地表下岩层,或者观测几十亿年前的微生物遗迹。在地球上识别古代微生物极为艰难,而且也无以令其所有人信服;在火星上,这种挑战就更大了。

For that reason, scientists have long called for a mission to bring rock and soil samples back to Earth for sophisticated analysis. The Mars mission scheduled for 2020 would begin the effort by experimenting with methods to select, lift and store promising samples.因此,科学家仍然敦促把火星岩石和土壤样本送回地球做到深入分析。2020年开始的火星计划将开始尝试挑选出、萃取和储存有期望的样本。But there are no Mars samples now — except those that arrive as long-traveling meteorites — so astrobiologists have to conduct their search for life using other methods and teasing out hidden evidence.但是目前还没火星样本——除了长途飞行回到地球的陨石——因此,宇宙生物学家不能用其他方法展开找寻生命的工作,辨别出有隐蔽的线索。

The search for water on Mars, for instance, goes back decades and many missions. But scientists were never certain that the carved canyons and deltas were results of water running long ago, or perhaps lava or frozen carbon dioxide. Because of Curiosity, there is now a wide consensus that early Mars had much water.比如,找寻火星水的工作在几十年前的火星计划中就开始了。但科学家仍然无法认同,那些大峡谷和三角洲到底是古代河流冲刷构成的,还是熔岩或失效的二氧化碳导致的。好在了“奇怪号”,现在科学家广泛表示同意,早期火星上有很多水。This conclusion has been difficult to square with climate models, which point to a colder early Mars with a thin atmosphere that could not have supported large bodies of standing water, or rivers that ran for millions of years. But faced with mounting evidence of longstanding water and consequently warmer conditions, the climate scientists have gravitated toward two interwoven explanations — both with implications for early life.这个结论一度很难在火星气候模型中说道得合。


The first is that frequent volcanoes and meteorite impacts heated the planet substantially; volcanoes also emit gases known to synthesize into organic compounds. The second is that to explain the substantial water cycle required to keep many Martian lakes filled and rivers flowing, the planet needed a substantial ocean in its northern half. Large swaths of Mars north of its equator are one to three miles lower than the so-called southern highlands, and scientists have proposed that an ocean may have filled and molded the vast depression. Others disagree on several grounds, including that no remnant shoreline has been detected.第一种说明是,频密的火山活动和陨石碰撞让星球大幅度加剧;火山也不会释放出来气体,能制备有机化合物。第二个说明是,火星要保持水循环,让火星湖泊和河流沦为有可能,那么在北半球就应当有一大片海洋。




也有人不表示同意,基于好几条理由,还包括没观测到海岸线的遗迹。“We don’t have hard evidence of a northern ocean, but our models require that much water to explain what the geologists have now confirmed,” said Michael A. Mischna of the Jet Propulsion Laboratory, another Curiosity team member. “What Curiosity has done is to bring together atmospheric and climate information with the findings of the geologists and geochemists, and created a broad and consistent story of a very wet early Mars.”“我们没找到北半球海洋的确凿证据,但我们的模型拒绝有一大片水体,这样才能说明目前地质学家早已证实的结论,”“奇怪号”团队成员、喷气前进实验室(Jet Propulsion Laboratory)的迈克尔·A·米什纳(Michael A. Mischna)说道。“奇怪号的工作就是将大气与气候信息,和地质学家与地质化学家的找到统合一起,建构一个大跨度、可以自圆其说的理论,叙述一个十分湿润的早期火星。

”While the evidence for water has become increasingly clear, the question of organic compounds is in flux. Such chemicals fall onto Mars all the time in interstellar dust and meteorites, as they do onto Earth. Yet none have been definitively detected.关于水的证据早已更加确切了,但有关有机化合物的疑惑还有一大堆。这类物质大大以星际尘埃和陨石的形式落在火星上,就像落在地球上一样,但目前还根本没被佐证地找到。But on this mission, team members knew to look for a salt called perchlorate that has been demonstrated on Earth to destroy or transform organics in the presence of heat. Substantial amounts of perchlorate were found in Gale Crater, suggesting that if early Mars had organic chemicals and they survived eons of radiation bombardment, they are long since gone or they will remain very difficult to detect with current techniques.不过在这次火星探寻中,科学家告诉应当找寻一种叫作低氯酸盐的无机物。


The Sample Analysis at Mars instrument is designed to identify relatively simple organics that burn off as gases in its oven. But it also carries nine cups with a solvent that can alter more complex molecules (like amino acids and nucleic acids) in ways that protect their signature.火星样本分析设备是用来辨识比较非常简单的有机物的。这些有机物将在它的烤炉内作为气体燃尽。但它也具有九个杯子,丰着一种溶剂,可以转化成更加简单的分子(比如氨基酸和核酸)同时维护它们的化学特征。This “wet chemistry” has been awaiting the finding of a sample rich in organics. A further problem is that one of its cups leaked, causing enormous headaches and making team leaders wary.这种“滑化学”技术仍然还在等候含有有机物的样本被找到。

另一个问题是设备的其中一只杯子再次发生了外泄,生产了大麻烦,让团队负责人不安心。But Dr. Glavin, a member of the team, hopes the spilled solvent will itself be used to test previously collected Martian samples, making it the first wet-chemistry experiment ever on another planet.但团队成员格莱文期望,溢洒的溶剂可以被用来测试之前收集的火星样本,那将是外星球展开的第一次滑化学试验。Clearly, the search for life on Mars — past or present — will be neither straightforward nor swift.很似乎,找寻火星生命——无论是古代生命还是现今的生命——会是一帆风顺,也不有可能立刻顺利。



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