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Small Innovative Missions for Planetary Exploration

HALO: Hydrogen Albedo Lunar Orbiter

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HALO: Hydrogen Albedo Lunar Orbiter
The Moon breathes hydrogen: solar wind protons and micro-meteoroids deliver hydrogen to the lunar surface at local rates that depend on surface composition, local topography, and the presence of structures such as magnetic anomalies. The impinging hydrogen directly affects the surface by weakening the solid state structure as it creates defects in the lattice causing space-weathering of the surface. Because the lunar surface is generally saturated with hydrogen, the implanted hydrogen escapes the surface and forms the hydrogen exosphere through a variety of processes including sputtering, recoil, and diffusion - giving the surface an effective hydrogen "albedo." These processes can lead to hydrogen deposition into cold traps and the formation of OH, and possibly water, through chemical alteration of oxygen-bearing minerals. Exospheric hydrogen is reclaimed by the solar wind as picked-up photoions and charge-exchange products. The exact pathway for each of these processes remains unknown, especially at regional scales, and quantifying each of these processes in this 'lunar hydrogen cycle' as a function of solar zenith angle and plasma and space environment will lead to a unified understanding of the plasma, exospheric, and geologic Moon. Furthermore, these are fundamental processes that contribute to the transport and production of volatiles, including water, throughout the solar system. More »

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