火星上有甲烷！（图）   

夏季期间，火星局部冒出一缕缕高浓度甲烷气体（见红色及黄色区域）。

Mars Has Methane, But Life?

It's taken 5 years, but planetary scientists are finally confident that they have detected methane on Mars. At a press conference today at NASA headquarters in Washington, D.C., and in a paper published online today in Science, researchers announced that all the painstaking observations, analysis, and reanalysis now reveal summertime plumes of the gas from three regions on the planet. On Earth, methane is a byproduct of living bacteria, but whether that's what's producing the gas on Mars is anyone's guess.	行星科学家们花了5年的时间，他们最终确信在火星上发现了甲烷。今天，在华盛顿哥伦比亚特区美国国家航空航天管理局总部的一次新闻发布会上，以及在今天《科学》杂志的在线版上，研究人员宣布：现在所有艰辛的观测、分析和再分析显示，火星上三个地区在夏季冒出一缕缕的甲烷气体。在地球上，甲烷是活菌产生的副产品。然而，火星上的甲烷是否也是细菌产生的呢？这一点谁都猜不透。
The first news of martian methane claims came in 2004 . But the early data--from spacecraft and ground-based telescopes--were controversial. Spacecraft were not detecting all of the spectroscopic signatures of the gas, for example, and ground-based observers had to contend with interference from methane and other trace gases in Earth's atmosphere.	最初宣布火星甲烷的消息是在2004年，但是早期来自太空船和地面望远镜的资料产生了争议。例如，太空船并没有发现甲烷气体所有的光谱信息，后来地面观测人员不得不认为那是来自地球大气中甲烷和其他微量气体的干扰。
At today's press conference, astronomer Michael Mumma of NASA's Goddard Space Flight Center in Greenbelt, Maryland, declared success. "We've eliminated most of the gremlins that were bothering us," he said. The biggest problem was working out how to reliably remove terrestrial contamination from the team's spectra. "We've done a lot of work that makes the current results robust," Mumma says. Planetary scientist Sushil Atreya of the University of Michigan, Ann Arbor, agrees. Measuring martian methane "is really at the ragged edge of things," he says, but "I think the detection is pretty solid."	美国国家航空航天管理局戈达德太空飞行中心位于马里兰州的格林贝尔特市，该中心的天文学家迈克尔·穆马在今天的新闻发布会上宣布说：他们成功地发现了甲烷。“我们排除了一直困扰我们的绝大多数障碍，”穆马说。最大的问题是搞明白如何确保把来自地球的污染从研究小组的光谱资料中剔除。“我们做了大量的工作，使目前的研究结果富有说服力，”穆马说。密歇根大学安娜堡分校的行星科学家苏什尔·阿特莱雅同意穆马的说法。“探测火星甲烷实属边缘问题，”阿特莱雅说，“但是我认为该探测结果是相当可靠的。”
Beyond detection, the observations reveal that the methane averages 33 parts per billion in the summer but essentially disappears afterward. About 0.6 kilograms of methane emerge each second in the summer, Mumma said, which is comparable to the emissions from a natural oil seep near Santa Barbara, California. Perhaps, he said, the martian methane is continually produced beneath the surface but only released when summer warming breaks an icy seal on the surface.	除了探测之外，多次观测也显示，夏季甲烷的平均浓度为十亿分之33，但是夏季过后甲烷就基本消失。穆马称，夏季每秒钟散发出的甲烷为大约0.6千克，相当于加州圣塔芭芭拉附近天然油渗漏处的散发量。穆马说，也许火星甲烷不断地产生于地面之下，但是只有当夏季的升温打开了表面上的一处冰封之后，甲烷才能冒出来。
The source? No one can say. Methane-generating bacteria might be living off hydrogen produced by rock, as studies kilometers down in South African gold mines have shown. Or, purely inorganic reactions between water and rock rich in the mineral olivine could do it, as found in hot springs near the Mid-Atlantic Ridge. Either way, the methane could have been produced ages ago, noted Mumma's colleague Geronimo Villanueva of Goddard, and been trapped in deep ice until warming released it. The next chance for nailing down the methane's origins may come in 2011 when the Mars Science Laboratory rover launches with the ability to measure the isotopic composition of the gas.	甲烷是如何产生的呢？谁也说不清。产生甲烷的细菌可能依靠岩石释放的氢为生，就象在南非金矿中数公里以下进行的研究所显示的那样。或者，水和富含橄榄石的岩石之间发生的纯粹的无机反应也可以产生甲烷，就象在大西洋中部山脊附近的温泉中所发现的情况。穆马的同事、戈达德太空飞行中心的杰若尼莫·维拉努瓦指出：不管是哪一种情况，甲烷可能是多年前产生的，被困在厚厚的冰层之中，直到升温之后才能释放出来。下一次确定甲烷来源的机会可能要等到2011年，到那时将要发射“火星科学实验室” 探测器，该探测器有能力测量这种气体的同位素成分。