| Autor: |
Dementyeva, N.N., Kurt, V.G., Smirnov, A.S., Titarchuk, L.G., Chuvahin, S.D. |
| Zdroj: |
Icarus; October 1972, Vol. 17 Issue: 2 p475-483, 9p |
| Abstrakt: |
The results of measurements of uv emissions in the Martian upper atmosphere in the wavelength ranges of λλ 1050–1340 Å and 1225–1340 Å, which were obtained by means of equipment mounted on the Mars 2 and Mars 3 artificial satellites, are presented. During communication, the minimum distance from the Martian surface was 1178 km and the maximum was 4100 km. Over the whole flight the intensity of the emission in the Ly α (1215.8 Å) line changed from 4.5kR (when the instrument's optical axis was directed to the limb of the Martian disk) to 700 R, before background subtraction, at maximum distances. Emission in the OI λ 1304-Å triplet lines was observed when the instrument's optical axis was directed to the sunlit side of the Martian surface and sharply decreased once the optical axis intersected the Martian limb. The maximum intensity in λ 1304 Å was 0.7 kR. The measurements of the Ly α sky background carried out at great distances from the center of Mars (15 000 km; 30 000 km; 52 000 km; 150 000 km) gave values of about 600 R. To construct a model of the neutral hydrogen distribution in the Martian atmosphere, the theory of radiative transfer in an optically thick medium was applied. The observational results are in good agreement with the theoretical calculations for the intensity in Ly α, using a model of neutral hydrogen with atomic density at the critical level of nc= 6 × 1023cm−3and with an exospheric temperature T∞= 350 K. The albedo of the hydrogen atmosphere layer in the Ly α line below 200 km is equal to 40%. The total vertical optical thickness above 200 km equals 1.2. A table of the atmospheric hydrogen density value found in measurements from Mariner 6 and 7. The escape time of hydrogen from the Martian atmosphere is small (several days). If one assumes that the neutral hydrogen concentration is, in general, determined by water vapor dissociation (the abundance of which is subjected to sharp variations), then the above-mentioned differences in density between our measurements and those of the year 1969 can be explained by decreasing the water vapor content in the lower layers of the Martian atmosphere, giving agreement with the direct measurement carried out at the same time. |
| Databáze: |
Supplemental Index |
| Externí odkaz: |
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