The Curiosity rover discovered that the chemistry of ancient Mars could have supported simple microbes more than three billion years ago, about the time that life first arose on Earth, scientists from the National Aeronautics and Space Administration said Tuesday.

The scientists based their claim on a rock sample mined from Mars last month by NASA's $2.5 billion Curiosity rover, which has been exploring the planet since August. In the grit of fine-grained mudstone, the scientists identified sulfur, nitrogen, hydrogen, oxygen, phosphorus and carbon─some of the key chemical ingredients for conditions suitable for life.

The scientists said the locale was almost certainly a primordial lake bed, rich in clay minerals, where the water many eons ago wasn't too salty or alkaline for life to thrive.

'We have found a habitable environment which is so benign and supportive of life that if you had been on the planet, the water would have been pure enough to drink,' said planetary scientist John Grotzinger, at the California Institute of Technology, who is the mission's project scientist. 'This is an environment that a microbe could have lived in and even prospered in.'

NASA's chief Mars scientist Michael Meyer said the chemical evidence unearthed by the one-ton, six-wheeled mobile laboratory demonstrated that the area, known as Gale Crater, once had 'all the prerequisites to support life.'

If the claim is true, this is the first place beyond Earth known to have been favorable for organic life.

'I think this is probably the only definitively habitable environment that we have described and recorded,' said David Blake, a scientist at NASA's Ames Research Center in Mountain View, Calif., who works with the rover's onboard laboratory.

Of the grayish-green powdered rock sample that the rover analyzed, he said, 'This is what we call pay dirt.'

Even so, there is still no evidence that life ever existed on Mars, the scientists said. The planet today is cold, arid and lifeless, bathed in sterilizing radiation.

Moreover, the Curiosity rover, which is equipped with 11 scientific instruments to probe for conditions suitable for life, isn't designed to detect the signs of microbial activity or any traces of fossilized bacteria.

'We are not a life-detection mission,' Dr. Grotzinger said. 'If there was microbial metabolism going on, we would not be able to detect that.'

美国国家航空航天局(NASA)的科学家周二说，“好奇号”(Curiosity)探测器发现，超过30亿年前，远古火星上的化学物质可以支持简单微生物存活。这一时间与地球上出现生命的时间差不多。

NASA/Associated Press“好奇号”采集的火星岩石粉末。照片由NASA发布。科学家们依据的是上个月由“好奇号”火星探测器采集来的岩石样本。“好奇号”由NASA斥资25亿美元打造，从去年8月开始探测火星。在精细研磨过的泥岩粉末中，科学家发现了硫、氮、氢、氧、磷和碳，这些都是适宜生命生存的关键化学成分。

科学家们说，几乎可以肯定这块岩石曾位于一个原始湖床，那里富含粘土矿物，多年之前，水中的盐硷含量没有那么大，生命可以在那里存在。

加州理工学院(California Institute of Technology)的行星科学家格罗青格(John Grotzinger)说，我们发现了一个适合生命存在的良好的宜居环境，如果你曾经生活在这个星球上，那里的水足够纯净，完全可以饮用。格罗青格是此次探测任务的项目科学家。他说，这是一个可能有微生物生存甚至繁衍的环境。

NASA的首席火星科学家迈耶(Michael Meyer)说，这个一吨重、六个轮子的移动实验室所发现的化学物质证明，盖尔环形山(Gale Crater)地区曾经拥有支持生命存活的所有必要条件。

如果上述观点为真，这将是人类在地球之外发现的第一个适合有机生物生存的地方。

加州山景城的NASA艾姆斯研究中心(NASA Ames Research Center)的科学家布莱克(David Blake)说，我认为这可能是我们描述并记录过的唯一一个确定适宜生命生存的环境。布莱克与探测器上的实验室开展合作。

他在提到探测器分析的灰绿色粉末状的石头样本时说，这真是有价值的发现。

科学家说，即便如此，仍然没有证据证明火星上曾经存在过生命。如今，这颗行星冰冷、贫瘠、死寂，笼罩在致命的辐射中。

此外，“好奇号”火星探测器的设计初衷并不是检测微生物的活动迹象或是任何细菌化石的踪迹。“好奇号”上配有11个可以探测适宜生命存在的环境的科学仪器。

格罗青格说，我们的任务不是探测生命，如果火星上进行着微生物的新陈代谢，我们也没有办法检测出来。