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The Mineral Composition of Rocks at the Landing Sites of Venera 13 and Venera 14 Descending Modules: Thermodynamic Calculations
| Content Provider | Semantic Scholar |
|---|---|
| Author | Barsukov, V. L. Khodakovsky, I. L. Volkov, Vladislav Pavlovich Sidorov, Yu. I. Borisov, Michael Vladimirovich |
| Copyright Year | 1983 |
| Abstract | OF VENERA 13 AND VENERA 14 DESCENDING M0DULES:THERNIODYNARlIC CALCULATIONS. V.L.Barsukov 1 ) ,I.L. Khodakovsky 1 ) ,V. P.Volkov 1 ) , Yu.I.Sidorov l),M.V.Borisov 2). 1)Vernadsky Institute of Geochemistry and Analytical Chemistry,USSR Academy of Sciences,Moscow, 2)Moscow State University,USSR. The space probes Venera 13 and 14 successfully landed on the Venustsurface in March 1982 and performed a vast program of atmospheric and planetary surface exploration. The elemental chemical composition of Venusian soil was firstly obtained by the X-ray fluorescent device on Venera 13 and 14 descending modules r4 1 L'J Thus, the theoretical calculation of mineral composition at the landing sites was carried out. The phase composition in the 16-component global system (atmosphere surface rock)open with respect to H,0,C02,C0,S02,HC1,Hl?, with the as contents corresponding to the known instrumental data[2-6 d . It was found that such constraints led to the incorporation of sulfur and chlorine in Venust minerals, in the concentrations several times higher than in real soi1[7]. This could be interpreted as the disequilibrium of the calculated global system with respect to SO2 and HC1. Thus, the estimation of mineral composition of Venust soil was performed according to the assumption of inert behavior of Sorand HC1: the sulfur content of rock was taken as 0.65 wt%(Venera 13) and 0.30 wt%(Venera 14). The system was considered open with respect to other volatiles. According to the calculations 2n question the rock at the landing site of v 44and corresponds to the altered alkaline basalt while that of Vene14 to the altered tholeitic basalt. The secondary minerals are represented by magnetite, anhydrite, marialite and sylvine. Some fraction of magnetite may be of primary origin. The calculated equilibrium compositions at different hypsometric levels (0,5,10 km) supported our previous conclusions on the formation of pyrite instead of anhydrite at lower P and T values depending on the datum level i.e. in the highlands r81. The equilibrium composition of the rock in the interaction with the oxygen-bearing atmosphere in accordance with the 18ppm 02determination in Venera 13 and 14 experimentL31 was found to be similar to the first calculation set excluding the complete substitution of magnetite for hematite. Thus, the a tmospher ic l i thospher ic interaction on Venus could be considered as the agent of a number of exogenic geochemical processes: the oxidation of Fe-silicates with the formation of ma netite or even hematite; the formation of secondary sulfates f anhydrite) or sulfides (pyrite); the chlorine is predicted to form marialite and sylvine; the fluorine could be bound in F-apatite. The presence of Fe-oxides is suggested as the result of chemical interaction of the atmospheric water vapor and crustal rocks in geological past, Thus, the Venust crust could be considered as the sink of oxygen while the deliberated hydrogen is dissipated from the upper atmosphere. The current estimates of D/H ratio in the Venust atmosphere [9,10] conform to the above assumption. The hydration of surface rocks under the conditions of low water vapor content ( x ~ , ~ = ~ o ~ ) is not revealed as well as the carbonatization of primary rocks. |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | https://www.lpi.usra.edu/meetings/lpsc1983/pdf/1010.pdf |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
