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1.
A critical analysis of the methods and results of estimating the optical thickness of the dust component in the Martian atmosphere 0, the particle size r
0, and the imaginary part of the refractive index n
ihas shown the following. (1) Observational data on the brightness distribution over the Martian disk as well as the phase dependences of diffusely reflected light and the azimuthal dependences of diffusely transmitted light are most appropriate to use only for verifying the reliability of the aerosol parameters determined by other methods. (2) If the morning and evening fogs in the atmosphere are disregarded, the Bouguer–Lambert–Beer method used to analyze the solar-brightness attenuation measured on the planetary surface yields overestimated extraatmospheric solar intensity I
0and atmospheric optical depth 0. At the Viking 1landing site, I
0and 0could be overestimated by a factor of 1.7 and by 0.35, respectively. (3) The aerosol size determined by analyzing measurements of the azimuthal dependences for the Martian sky brightness at low elevations of the Sun most likely corresponds to the fog particles. (4) If overestimated values of I
0were used to standardize the observations of the solar radiation transmitted by the Martian atmosphere, then n
iwere also overestimated; using overestimated 0also affected the reliability of the latter. (5) The problem of reliability of the available 0and r
0estimates for periods of high atmospheric transparency is yet to be solved. For the highest activity of the dust storm in 1971, it was found that 4.5 r
0 7.5 m for the lognormal particle size distribution with 2= 0.2 and the optical thickness of a dust cloud 0 15. (6) The spectral values of the apparent albedo of Mars measured in October 1971 at a phase angle of 42° in the spectral range 0.250 0.717 allowed the imaginary part of the refractive index to be estimated in terms of a model of a dust cloud composed of spherical particles with the lognormal size distribution with r
0= 4.5 m and 2= 0.2. 相似文献
2.
Dlugach Zh. M. Korablev O. I. Morozhenko A. V. Moroz V. I. Petrova E. V. Rodin A. V. 《Solar System Research》2003,37(1):1-19
Atmospheric aerosols play an important role in forming the Martian climate. However, the basic physical properties of the Martian aerosols are still poorly known; there are many contradictions in their estimates. We present an analytical overview of the published results and potentialities of various methods. We consider mineral dust. Zonally averaged data obtained from mapping IR instruments (TES and IRTM) give the optical thickness of mineral aerosols 9 = 0.05–0.1 in the 9-m band for quite atmospheric conditions. There is a problem of comparing these estimates with those obtained in the visible spectral range. We suggest that the commonly used ratio vis/9 >2 depends on the interpretation and it may actually be smaller. The ratio vis/9 1 is in better agreement with the IRIS data (materials like montmorillonite). If we assume that vis/9 = 1 and take into account the nonspherical particle shape, then the interpretation of ground-based integrated polarimetric observations ( < 0.04) can be reconciled with IR measurements from the orbit. However, for thin layers, the sensitivity of both methods to the optical thickness is poorly understood: on the one hand, polarimetry depends on the cloud cover and, on the other hand, the interpretation of IR measurements requires that the atmospheric temperature profile and the surface temperature and emissivity be precisely known. For quite atmospheric conditions, the local optical-thickness estimates obtained by the Bouguer–Lambert–Beer method and from the sky brightness measured from Viking 1 and 2 and Mars Pathfinder landers are much larger: = 0.3–0.6. Estimates of the contrasts in images from theVikingorbiters yield the same values. Thus, there is still a factor of 3 to 10 difference between different groups of optical-thickness estimates for the quiet atmosphere. This difference is probably explained by the contribution of condensation clouds and/or by local/time variations. 相似文献
3.
The influence of the shape of dust aerosol particles in the Martian atmosphere on the imaginary part of the refractive index n
i as derived from photometric observations during the period of the highest activity of the dust storm in 1971 was studied and exemplified for particles of spherical and oblate spheroidal shape. A similar analysis was performed for mean particle radii r
0 and optical thicknesses 0 of the dust layer estimated from polarization observations for periods of high atmospheric transparency. It was demonstrated that the values obtained for these optical parameters are affected by the adopted aerosol shape. Namely, the values of n
i, r
0, and 0 found for spheroidal particles proved to be nearly twice as large as those for spheres. However, they are still much less than the available estimates of these parameters inferred, in particular, from interpreting space experiments. The reason for this difference needs further investigation. 相似文献
4.
Principal Astronomical Observatory, Ukrainian Academy of Sciences. Translated from Astrofizika, Vol. 34, No. 3, pp. 403–418, May–June, 1991. 相似文献
5.
O. G. Epshtein A. G. Dlugach A. V. Starovoytov B. F. Romanyuk 《Lithology and Mineral Resources》2011,46(2):115-134
The areal geological-geophysical study of Quaternary sediments was carried out in two areas of the eastern Barents Sea (Central
Deep and Murmansk Bank). This communication is mainly dedicated to the results of seismoacoustic investigations. It has been
established that the Quaternary sequence unconformably overlying the pre-Cenozoic strata in the studied areas is as follows
(from bottom to top): marine-glaciomarine Late Glacial-Holocene sediments, massive diamictons (the main part of the section),
and glaciotectonites formed after the underlying Mesozoic unconsolidated sediments. The Pleistocene diamictons, origin of
which is still debatable, are the main studied object. They constitute two seismostratigraphic complexes (SSC). According
to the accepted stratigraphic subdivision, they are represented by the Upper Weichselian SSC III (Maximum Last Glaciation)
and Lower Weichselian SSC V (Middle Weichselian SSC IV is eroded here). Complexes SSC V and SSC III composed of till overlie
the older sediments with the exaration unconformity. Complex SSC V is preserved locally, while SSC III is characterized by
the regional distribution. Complex SSC III is universally enveloped unconformably without erosional surface by an acoustically
uniform thin-bedded member of Late Glacial-Holocene glaciomarine and marine sediments (SSC II+I). Unlike SSC V, SSC III demonstrates
lateral heterogeneity in both studied areas consisting of two seismofacies, one of which forms very specific acoustically
transparent bodies (ATBs). Sediments of SSC III avoided subsequent erosion. Therefore, their glacial nature is distinctly
reflected in the complex distribution of thickness and peculiar morphology of corresponding bodies. 相似文献
6.
Translated from Astrofizika, Vol. 36, No. 1, p. 163, January–February, 1993. 相似文献
7.
8.
The influence of various factors on the interpretation of polarimetric observations of Mars performed under high-transparency atmospheric conditions was investigated. It was demonstrated that the technique proposed by Morozhenko (1974) for the data interpretation does not allow the optical characteristics of cloud particles to be estimated unambiguously. In particular, it turns out that both the model of a thin layer composed of very small silicate particles and the model of very small ice particles in a thin layer fit the data of measurements at a phase angle of 25°. Numerical simulations showed that reliable information on the reflectance characteristics of the Martian surface in a wide spectral range, including blue and ultraviolet wavelengths, is necessary to obtain reliable estimates of aerosol optical properties. Our calculations confirmed that the scattering on ice-cloud particles could introduce a significant ambiguity in the interpretation of the available polarimetric data. Besides, small particles, both ice and silicate, existing in the upper atmospheric layer can substantially mask the layer of larger particles below, which becomes invisible for remote sensing. 相似文献
9.
10.
O. G. Epshtein A. G. Dlugach A. V. Starovoytov B. F. Romanyuk 《Lithology and Mineral Resources》2011,46(3):220-249
Llithology of massive diamictons was studied in two areas of the eastern Barents Sea using cores and geophysical data. These
sediments dominate in the Pleistocene section as two seismostratigraphic complexes (SSC): Upper Weichselian (SSC III) and
locally distributed Lower Weichselian (SSC V). Diamictons of these complexes represent tills produced by the geological activity
of the Pleistocene Novaya Zemlya and Scandinavian ice sheets. The Upper Weichselian glacial sequence is laterally heterogeneous.
It includes two seismic facies represented by ordinary (overconsolidated) tills (they also constitute SSC V) and a spacious
moraine of the specific type with the normally consolidated sediments (they avoided compaction by the ice load) and certain
lithological specifics. The last glacial sediments were formed in a specific subglacial setting similar to the sediments under
fast ice streams of Antarctica. However, the specific features allow us to define these sediments as a new (Barents Sea) facies
of tills related to zones of intense basal melting of glaciers. 相似文献