在那一时期，火星地表或许不会一直都有水存在，格罗青格博士指出，但会存在地下水，即便地表暂时干涸。
The surface may not have been wet for all of that period, notes Dr Grotzinger, but groundwater could have persisted even when the surface was temporarily dry.
格罗青格博士是NASA火星科学实验室任务的首席科学家，该任务的漫游车——好奇号于去年在火星着陆。
Dr Grotzinger is the chief scientist for NASA's Mars Science Laboratory mission, whose rover, Curiosity, landed on the planet last year.
人物：欢喜冤家西蒙·佩吉和尼克·弗罗斯特（《僵尸肖恩》）携手为天外来客配音的赛斯·罗根（《青蜂侠》），格雷格·莫拉托执导。
Talent: Comedy duo Simon Pegg and Nick Frost (Shaun of the Dead) team up with Seth Rogen (The Green Hornet), who voices the extraterrestrial. Greg Mottola (Adventureland) directs.
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