THE GEOCHEMICAL MODEL OF MARS - AN ESTIMATION FROM THE HIGH-PRESSURE EXPERIMENTS

Recent high pressure experiments on the model martian mantle provide firm constraints on the internal structure and chemistry of Mars. We examined the martian models proposed by Morgan and Anders (1979) and Dreibus and Wanke (1985) based on the mineral physics data obtained by the recent high pressure experiments. Original models proposed by these authors must be modified to reduce the mass fraction of the core and thus the bulk iron content of Mars in order to satisfy the geophysical constraints. We present a new model of the martian interior which satisfies the geophysical and cosmochemical constraints. Our model Mars is composed of a mixture of three components: 15.7% metal (M) component, 39.3% refractory silicate (R) component, and 45% volatile rich (V) component. The mass fraction of the core is 18.2 wt% and the bulk iron content is about 23 wt % in this model. The present analysis implies that the bulk iron content of Mars is significantly smaller than the iron contents of the other terrestrial planets and C1-chondrite. This suggests existence of some processes to fractionate iron and silicate in formation of the planets.