Asymmetric Space Weathering on Lunar Crater Walls

What is it about?

Space weathering is the alteration of an airless body’s spectral properties due to solar wind and micrometeoroid bombardment. Using new topography-corrected spectral data from the SELENE spacecraft, here we report a fundamental new property of lunar craters: the spectral properties of north, south, east, and west walls vary systematically across the Moon. We find that differences in the pole- and equator-facing walls vary with latitude, which we explain by reduced solar wind flux in pole-facing slopes. On the nearside, we find that east-west differences in crater wall color vary with longitude, which we explain by solar wind shielding as the Moon passes through the Earth’s magnetosphere. Because micrometeoroids are unaffected by magnetosphere passage, the longitudinal effect unambiguously discriminates between micrometeoroid and solar wind effects.

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