Shackleton Crater

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An impact crater straddling the lunar south pole, about 21 km across and 4.2 km deep, named after the Antarctic explorer Ernest Shackleton. Its floor is permanently shadowed and among the coldest measured places in the Solar System, while portions of its rim are sunlit for most of the lunar year — a combination that makes the rim a leading candidate for solar-powered surface infrastructure adjacent to a cold trap. Laser altimetry from the Lunar Reconnaissance Orbiter found the floor unusually reflective, which has been read either as a modest amount of surface ice or as fresh, unweathered regolith exposed by mass wasting; the ambiguity is unresolved. ShadowCam on the Korean Danuri orbiter has since imaged the shadowed interior by earthshine and scattered light.