Ronald J. Vervack

Chapter 13 – Mercury

Mercury is the innermost planet, with a high density and large metallic core. It is the only terrestrial planet besides Earth with an internally generated magnetic field, which gives rise to a complex magnetosphere. Mercurys surface is heavily cratered and has also been modified by volcanism, including pyroclastic volcanism. Surface compositions are similar to komatiites and basalts on Earth, but highly depleted in iron, which is located mostly in the planets core. Mercurys tectonics is dominated by compressional deformation driven by global cooling and contraction. The planets surface is surprisingly rich in sulfur and other volatiles, whose mobility at high surface temperatures creates erosional topographic hollows. Regions of permanent shadow near the poles trap water ice and low-albedo volatiles, possibly supplied by infalling comets and asteroids. The thin exosphere is populated with atoms removed from the surface by solar radiation, charged particle sputtering, and micrometeoroid bombardment.