Spectroscopic signatures of water (H2O) and hydroxyl radicals (OH) have been observed on surfaces of asteroids such as 1 Ceres, 24 Themis, 433 Eros, over the last decades. However, the lifetime of the exposed water ice is relatively short at distances of the inner asteroid belt – i.e. on the order of only 104 to 106 years. Hence no spectroscopic signatures of water should survive on these objects, particularly for S-type asteroids. Therefore, mechanisms must exist to replenish the water. However, the sources of regenerative water ice on asteroids are still elusive. Here we report that the regeneration of surface water at asteroid relevant temperatures necessitates a simultaneous exposure by energetic electrons and laser irradiation – energetic electrons simulate the cascade of secondary electrons generated by the solar wind and galactic cosmic ray particles penetrating the minerals, while laser irradiation represents an analog to micrometeorite impact exposure. A single component space weathering is insufficient to generate surface water at low temperatures. Experimental results support our hypothesis that spectroscopic signatures of water can be regenerated on airless bodies over a timescale of less than 106 years.

Regenerative water sources on surfaces of airless bodies

2019 Fall National Meeting

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