Thermal history of a Mercury with reduced composition and the possibility of dynamo in its outer core

Abstract

Several lines of evidence such as the reflection spectra of Mercury suggest that Mercury may consist of reduced materials. Therefore, we calculated the Mercury's thermal history assuming that the mantle and the core have the similar compositions to the silicate and metal-sulfide components of enstatite chondrite, respectively. We examined the possibility of the chemical convection in the liquid outer core, caused by the exclusion of light-alloying element associated with inner core growth. If the mantle convection occurs by dislocation creep, the inner core of Mercury does not grow. However, if the mantle convection occurs by diffusion creep and the grain size of mantle is smaller than 3 mm, the inner core grows during 4.5Gyr. In the latter case, the intrinsic magnetic field of Mercury may be explained.