Report

Evidence for Water Ice Near Mercury's North Pole from MESSENGER Neutron Spectrometer Measurements

Science  29 Nov 2012:

DOI: 10.1126/science.1229953

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Abstract

Measurements by the Neutron Spectrometer on the MESSENGER spacecraft show decreases in the flux of epithermal and fast neutrons from Mercury's north polar region that are consistent with the presence of water ice in permanently shadowed regions. The neutron data indicate that Mercury's radar-bright polar deposits contain, on average, a hydrogen-rich layer more than tens of centimeters thick beneath a surficial layer 10 to 20 cm thick that is less rich in hydrogen. The buried layer must be nearly pure water ice. The upper layer contains less than 25 wt.% water-equivalent hydrogen. The total mass of water at Mercury's poles is inferred to be 2 × 1016 to 1018 g and is consistent with delivery by comets or volatile-rich asteroids.

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