Toward the top (northern) end of the image, the ice becomes sparser, but the walls of a large impact crater in the upper-left corner provide a refuge for an oblong ice deposit on the crater floor.

接近照片顶部尽头(即北部)，冰雪变得较稀少，但是左上角一个巨大的撞击陨石坑壁却为环形山底的一块椭圆形积冰提供了庇护所。

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One possible option involves a so-called "refuge floor" at higher levels with extra structural or fire resistance.

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