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Fire & ice: What really happened to water on Mars

作者:屈突痃晟    发布时间:2019-03-14 04:02:01    

By Stuart Clark Watch a slideshow of images showing signs of water on Mars SINCE the Viking orbiters beamed back the first tantalising images of water-cut features on Mars in the 1970s, NASA’s mantra for the Red Planet has been simple: “follow the water”. Working out when Mars had liquid water on its surface, and where that water went, they reason, will provide vital clues about whether Mars could once have harboured life, and whether life could cling on today. Since then a long line of orbiters, landers and rovers have searched the Martian surface for signs of where water once flowed. The latest, NASA’s Phoenix lander, is scheduled to reach the surface of Mars on 25 May. If all goes well, it could be the first lander to actually hold Martian water in its robotic hands, and will answer some long-standing questions about the planet’s hydrological history. According to the conventional view, from soon after its formation about 4.5 billion years ago until 2 to 2.5 billion years ago, Mars was a watery world like Earth, with luxuriant seas, perhaps even an ocean, that might have supported life. These large bodies of water were gradually lost through climate change, caused by a decline in volcanic activity and the whittling away of the planet’s atmosphere by radiation from the sun. Some water remained frozen in the polar caps, but most drained downwards into the rocks and froze. While there can be no mistaking that water did exist on Mars in large quantities, as new information from Mars’s many probes and landers comes in,

 

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