Photographic evidence suggests that liquid water once existed in great quantity on the surface of Mars.

照片证据表明，液态水曾大量存在于火星表面。

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The gravity on the surface of Mars is about one third as strong as it is on earth.

火星表面的引力大约是地球表面引力的三分之一。

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Recent orbital images show that water might still occasionally flow on the surface of Mars.

最近的轨道照片显示水仍然偶尔流过火星表面。

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He said he could see changes in the seasons on the surface of Mars.

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We now have the ability to put remote control cameras on the surface of Mars.

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While high profile activities continue on the surface of Mars, other research is digging a little deeper.

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The rover, after traveling for more than eight months, safely landed on the surface of Mars before 2 a.m.

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