火星首现湖岸线 可能存在生命迹象

US researchers have uncovered traces of an ancient lake on Mars boosting hopes of discovering evidence that billions of years ago the Red planet hosted life.

The lake, which dates back some 3.4 billion years, appears to have covered as much as 80 square miles and was up to 1,500 feet deep, said the team from the University of Colorado.

"This is the first unambiguous evidence of shorelines on the surface of Mars," said Boulder's research associate, Gaetano Di Achille, in a study published in the latest edition of Geophysical Research Letters.

"The identification of the shorelines and accompanying geological evidence allows us to calculate the size and volume of the lake, which appears to have formed about 3.4 billion years ago."

Analysis of the images has shown the water carved out the canyon in which it was found, which then opened out into a valley depositing sediment which formed a delta.

"Finding shorelines is a holy grail of sorts to us," said assistant professor Brian Hynek, adding it showed the lake existed at a time when Mars was thought to have been cold and dry.

Scientists believe the oldest surfaces on Mars formed during the wet and warm era known as the Noachan epoch, about 4.1 billion to 3.7 billion years ago, that featured a bombardment of large meteors and extensive flooding.

The newly discovered lake is believed to date from the Hesperian era and postdates the end of the warm and wet period on Mars by 300 million years, according to the study.

Scientists believe deltas next to the lake may well hold secrets about past life on Mars as such places on Earth have become the natural deposits of organic carbon and other markers of life.

美国研究人员日前在火星上找到了一个古老湖泊的痕迹。这使人们在该红色星球上发现数十亿年前生命迹象的希望大大增强。

美国科罗拉多大学的研究小组称，科学家发现的湖泊距今已有34亿年历史，占地80平方英里，深达1500英尺。

科罗拉多大学波尔得分校的研究助理盖塔诺．迪亚克雷在研究报告中称：“这是首个证明火星表面有湖岸线的确凿证据。”这项研究成果在最新一期《地球物理学研究快报》上发表。

“湖岸线以及其它地质证据的发现，使我们可以计算湖泊的大小和容积。这个湖泊距今约有34亿年历史。”

对成像的分析显示，水流冲刷出了一条溪谷，这条溪谷与一个山谷相连，流水沉积物还形成一个的三角洲。

助理教授布莱恩．海尼克说： “对我们来说，在火星上发现湖岸线是一项重大收获。”他还补充称，研究表明湖泊存在于人们所认为的火星寒冷干旱期。

科学家认为，火星最古老的表面是在温暖湿润的诺亚坎时期形成的，距今约41亿到37亿年，这一时期火星表面遍布巨大的陨石坑和庞大的水系。

该研究表明，最新发现的这一湖泊是在赫斯伯利亚纪时期形成的，比火星温暖湿润季的结束还晚3亿年。

科学家认为，湖泊附近的三角洲可能完好地保存有生命存在的秘密，因为地球上类似的三角洲也是有机碳和其它生命标志物的天然寄存地。

Vocabulary:

holy grail：(传说耶稣在最后晚餐中用的)圣杯，圣盘

postdate: to occur later than; follow in time（在……之后到来, 填迟……的日期）