ISSN:
1365-246X
Quelle:
Blackwell Publishing Journal Backfiles 1879-2005
Thema:
Geologie und Paläontologie
Notizen:
A re-examination of the internal structure of Mars has been made in the light of revised observational data on the radius R. Taking the reduced value R=3330 km, and the mass of Mars as 6.442 ± 1026 g, the hypotheses (a) that the Earth and Mars have the same overall composition and (b) that Model B gives a satisfactory representation of the Earth's mantle, are examined. It is confirmed that the reduced value of the radius implies the presence of a significant proportion of uncombined iron in the mantle of Mars. The assumptions would also require the interior of Mars to deviate from a hydrostatic state, and if correct lend support to the view of Jeffreys that the material of Mars has finite strength. It is still possible for Mars to have a small iron (and/or nickel) core, the radius of which most probably does not exceed 700–900 km; the smaller the radius of the core, however, the less the deviation from a hydrostatic state.On hypothesis (a), the reduced radius further implies that the Earth contains uncombined iron outside the inner core. A provisional view was that this uncombined iron was located mainly in the outer core. Further calculation, however, gives rise to the speculation that it is the mantle of the Earth which contains this uncombined iron and not the outer core. A coherent picture can be derived by assuming that Mars and the mantle of the Earth both consist broadly of a mixture of uncombined iron with silicates or FeO, MgO, SiO2 phases. The Earth's outer core on this view would contain no uncombined iron, the latter having gravitated toward the centre to form the inner core. In this way, the hypothesis (a) can be reconciled with the reduced Mars radius and with a hydrostatic state. The corresponding density distribution (p g/cm3) in Mars is given approximately by p=4–68 -0.86x2, where x=r/R, r being the distance from the centre.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1111/j.1365-246X.1957.tb06693.x
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