Space Weathering Impact on Solar System Surfaces and Mission Science

Space weathering is the collection of physical processes acting to erode and chemically modify planetary surfaces directly exposed to space environments of planetary magnetospheres, the heliosphere, and the local interstellar environment of the solar system. Space weathering affects the physical and optical properties of the surfaces of planetary bodies, so understanding its specifics is critical for interpreting surface data from remote and landed measurements. For full coverage of space environmental measurements, we recommend expanded interdisciplinary cooperation between NASA’s Planetary Science and Heliophysics divisions. To grow the field in the next decade and maximize impact on mission studies, we suggest a balanced mixture of laboratory measurements, modeling, and theoretical investigations in support of all missions. Space Environments Vast expanse of the space weathering environment interacting with solar system bodies is illustrated in Figure 1 by logarithmic horizontal scale of radial distance from the Sun to αCentauri. Principal sources of energy for space weathering of planetary surfaces are UV photons, solar wind plasma, and energetic particles from the Sun, within a few hundred AU, and external sources of plasma and energetic particles entering into the solar system from the local interstellar environment. Beyond the realm of terrestrial planets and the asteroid belts, the solar influence significantly wanes with the decline in density of the expanding solar wind plasma and magnitude of the frozen-in magnetic field, while the interstellar influence progressively grows through interaction of interstellar neutral winds with solar ultraviolet radiation and the solar wind plasma. Across the heliospheric boundary region near 100 AU, now being explored by the two Voyager spacecraft, occurs a transition from supersonic (400 – 800 km/s) plasma flows of solar coronal expansion, the solar wind, to 26 km/s inward flow of the interstellar wind. This plasma contains both a bulk flow and thermal components associated with typical ion energies up to a few keV, and energetic components extending to far higher energies, ultimately to the full range