Earth based radar observations hint at possible water ice in the pole craters, possible only because of permanent shadow.

地球上的雷达观测暗示，在极陨石坑可能的水冰，不仅是因为永久阴影可能。

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Finding the North Pole was "rather like stepping on the shadow of a bird hovering overhead."

踏进北极就象把脚踏上在空中盘旅程的鸟的影子一样。

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