答案可能是，现在火星上几乎所有的水都被锁在地表下的永久冻土层中，更多的水被包含在这个星球的极地冰帽中。
The answer may be that virtually all the water on Mars is now locked in the permafrost layer under the surface, with more contained in the planet's polar caps.
他们认为，处于地表下的油起源于远古，并是由海洋生物形成的。
They think that the oil under the surface of the earth originated in the distant past, and was formed from living things in the sea.
漫游者发现了分歧组成的分层的土壤层，具有地表下的水的迹象。
The rover found stratified soil layers of different compositions, with evidence of water below the surface.
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