MERCURY IMPACTOR: A mission to study below the surface

Kurzfassung

The surfaces of airless bodies like Mercury undergo processes of gardening, i.e. meteoritic bombardment, and regolith alteration, due to the direct and continuous exposition of the regolith to the solar and cosmic radiation. The long exposure to the meteoritic and to the energetic ion bombardments causes deep changes in the surface features. Eventually, to have a real knowledge of the body, it would be necessary to study the layers below the exposed surface, down to at least tens of meters. The most conventional method to investigate the underlying surface layers and composition is to use a drill in a probe/lander to the surface. On the contrary, producing an artificial fresh impact crater with a massive projectile hitting the surface would allow to access the subsurface material. Part of it volatilizes and can be measured remotely from an orbiting spacecraft. Part of it is ejected and re-deposited around the cavity, so that it could be analyzed and studied by remote sensing instruments. The present mission idea consists in launching a massive and high velocity projectile, able to volatilize an adequate surface volume and generate a crater of up to a hundred meters. The projectile should be built of a special alloy that would be easily distinguishable from the one of the planet surface. The science objectives of this mission will be to study i) the lower (and pristine) layers of the surface, ii) the impact by itself and its measurable consequences on the surface and iii) the variability induced in the exosphere due to the vaporization process.