So to maintain the topography of the south polar cap, there has to be water ice in there stiffening it up.

所以要想维持 南部冰冠的地形，就必须有冰水使其变得坚固。

The pinkish deposits constitute a vast south polar cap believed to contain methane ice, which would have reacted under sunlight to form pink or red compounds.

这些固态氮冰在阳光照射下会产生化学反应，生成粉色或红色的化合物。