HR: 14:00h
AN: P23A-03    [Abstracts]
TI: The Construction of Interior Structure Models of Mars
AU: * Gudkova, T V
EM: gudkova@ifz.ru
AF: Gudkova Tamara, Institute of Physics of the Earth, B.Gruzinskaya, 10, Moscow, 123995 Russian Federation
AB: Based on available chemical models of the planet (Wanke and Dreibus, 1994; Dreibus and Wanke, 1989; Lodders and Fegley, 1997; Sanloup et al., 1999; Lodders, 2000), a new set of global models of the Martian interior has been constructed. The model comprises four submodels - a model of the outer porous layer, a model of the crust, a model of the mantle and a model of the core. The first 10- 11 km layer is considered as an averaged transition from regolith to consolidated rock. The mineral composition of the crustal basaltic rock varies with depth because of the gabbro-eclogite phase transition. As a starting point for mantle modeling there have been used experimental data obtained by Bertka and Fei (1997,1998) along the areotherm, iron content of the mantle being varied. New high P-T measurements of the density of Fe, FeS and FeH enable us to refine the core model. Taking into account available chemical models and the fact that noticeable amount of hydrogen could enter the Martian core during its formation (Zharkov, 1996), such parameters as ferric number of the mantle (Fe&35;), sulfur and hydrogen content in the core are varied. If there is no hydrogen in the core, a model produces a Fe/Si ratio that is smaller than the chondritic value of 1.71. The presence of hydrogen in the core significantly increases the Fe/Si ratio up to about 1.7, and reduces the melting temperature of the core material. To satisfy the bulk chondritic ratio, more than 50 mol % of hydrogen must be incorporated into the core. Then, a problem of consistency of the cosmochemical DW model with the internal structure model of the planet is solved. It will confirm the idea that terrestrial planets were formed from chondritic material. This is a fundamental problem on the formation of Mars and its evolution. The determination of the core radius continues to be of great importance, in case of a reliable determination of the core radius uncertainties concerning the composition of Mars will be resolved. From cosmochemical point of view, it is difficult to assume that the core contains more than 20 wt % of sulfur. The radius of such core is about 1600-1700 km. Therefore, if the core of Mars turns out to be larger, hydrogen could be such an admixture element. According to numerical modeling hydrogen increases the core radius and decreases Fe&35; of the mantle.
DE: 6225 Mars
SC: Planetary Sciences [P]
MN: 2005 Joint Assembly