Backscattering of solar wind ions by a planetary surface is a fundamental process that may occur at all bodies exposed to the solar wind and unprotected by a thick atmosphere, that is, the Moon, Mercury, the moons of Mars, dwarf planets, asteroids, and comets. The overarching questions at stake include: (a) what are the key parameters that control the efficiency and angular distribution of solar wind ion backscattering, including solar wind parameters (density, bulk speed, temperature, composition) and surface properties (composition, density, porosity), (b) what can be learnt about a surface from the observation of backscattered particles, and (c) does the mass loading of backscattered ions upstream of an airless body influence its global interaction with the solar wind (e.g., Harada & Halekas, 2016)?At the Moon, JAXA's Nozomi, JAXA's Kaguya, ISRO's Chandrayaan-1, and NASA's ARTEMIS missions have opened an era of detailed characterization of solar wind ion backscattering (e.g.,