Mercury’s permanently shadowed polar floors cradle water ice, revealed by MESSENGER data

Mercury’s cold polar crater floors hold water ice on permanently shadowed terrain, a conclusion supported by MESSENGER (2012) via radar-bright deposits, a hydrogen signal from neutron measurements, exposed versus buried ice seen in laser altimetry, and thermal models. Ice can be exposed in some areas and buried under a thin, dark cover in others; deposits may range from metres to tens of metres thick, and their age and origin remain topics of study, with delivery likely from comets/asteroids over hundreds of millions of years. The upcoming BepiColombo mission will map these regions in greater detail but will not land in the cold traps.