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Bobina, N. N.

Publications and source records attributed to Bobina, N. N..

6 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1993

Russia's contribution to regional geologic mapping of Venus

Geologic maps in Magellan C1-format were produced by six geologists and three cartographer in Russia during 1992. More sheets are in progress. The work is coordinated by Vernadsky Institute. The Magellan SRR images in form of C1-format photomaps were used as a base for geologic-geomorphic regional mapping of Venus at approximately 1:8,000,000 scale. This work took place in Russia at Vernadsky Institute and at the Department of Geology, Lomonosov Moscow University. The aim is to produce a preliminary geologic survey of Venus with the new high resolution images obtained by Magellan. It took place at the cartographic division, Laboratory of Comparative Planetology and Meteoritics, Vernadsky Institute, Russsia's Academy of Sciences.

Burba, G. A.↗
NASA NTRS1993

Beta Regio rift system on Venus: Geologic interpretation of Magellan images

Magellan SAR images and altimetric data were used to produce a new geologic map of the Northern part of Beta Regio within the frames of C1-30N279 mapsheet. It was part of our contributions into C1-formate geologic mapping efforts. The original map is at 1:8,000,000 scale. The rift structures are typical for Beta Regio on Venus. There are many large uplifted tessera areas on Beta upland. They occupy areas of higher topography. These tessera are partly burried by younger volcanic cover of plain material. These observations show that Beta upland was formed mainly due to lithospheric tectonical uplifting, and only partly was constructed by volcanic activity. A number of rift valleis traverse Beta upland and spread to the surrounding lowlands. The largest rift crosses Beta N to S. Typical width of rifts is 40 to 160 km. Rift valleis in this region are structurally represented by crustal grabens and half-grabens. There are symmetrical and asymmetrical rifts. A lot of them have shoulder uplifts with the relative high up to 0.5-1 km and width 40 to 60 km. Preliminary analysis of the largest rift valley structural cross-sections leads to the conclusion that it originated due to a 5-10 percent crustal extension. The prominent shield volcano - Theia Mons - is located at the center of Beta rift system. It could be considered as the surface manifestation of the upper mantle hot spot. Most of the rift belts are located radially to Theia Mons. The set of these data leads to conclusion that Beta rift system has an 'active-passive' origin. It was formed due to the regional tectonic lithospheric extension. Rifting was accelerated by the upper mantle hot spot located under the center of passive extension (under Beta Regio).

Nikishin, A. M.↗
NASA NTRS1993

Beta Regio - Phoebe Regio on Venus: Geologic mapping with the Magellan data

The geologic maps of C1-15N283 and C1-00N283 sheets were produced (preliminary versions) with Magellan SAR images. This work was undertaken as a part of Russia's contribution into C1 geologic mapping efforts. The scale of the original maps is 1:8,000,000, and the maps are reproduced here at a reduced size.

Nikishin, A. M.↗
NASA NTRS1992

Venus: Geology of Beta Regio rift system

Beta Regio is characterized by the existence of rift structures. We compiled new geologic maps of Beta Regio according to Magellan data. There are many large uplifted tesserae on beta upland. These tesserae are partly buried by younger volcanic cover. We can conclude, using these observations, that Beta upland formed mainly due to lithospheric tectonic uplifting and was only partly constructed by volcanism. Theia Mons is the center of the Beta rift system. Many rift belts are distributed radially to Theia Mons. Typical widths of rifts are 40-160 km. Rift valleys are structurally represented by crustal grabens or half-grabens. There are symmetrical and asymmetrical rifts. Many rifts have shoulder uplifts up to 0.5-1 km high and 40-60 km wide. Preliminary analysis for rift valley structural cross sections lead to the conclusion that rifts originated due to 5-10 percent crustal extension. Many rifts traverse Beta upland and spread to the surrounding lowlands. We can assume because of these data that Beta rift system has an active-passive origin. It formed due to regional tectonic lithospheric extension. Rifting was accelerated by upper-mantle hot spot origination under the center of passive extension (under the Beta Regio).

Nikishin, A. M.↗
NASA NTRS1988

The structure of the Martian cryolithosphere upper levels

Structural inhomogeneities of the Martian cryolithosphere upper levels were studied by the proposed crater method. On the basis of analysis of 127 photomaps of 1:2 million scale morphological and morphometrical parameters of all the fresh craters larger than 1 km in diameter with fluidized ejecta and without it were investigated. Using the parameters of the craters, the roof depths of ice-bearing rocks were estimated and the data on the ice relative constant in the excavated permafrost layer were obtained. These data were used for the construction of maps of the boundary depth between ice-free nearsurface layer and ice-bearing rocks. A series of maps of the relative ice content for individual permafrost horizons was constructed. It was deduced from the obtained maps that the zone of the dryest nearsurface rocks on Mars is in the latitude belt + or - 30 degrees where maximum floor depths of the ice-bearing rocks vary from 400 to more than 400 m. It was found that the thickness of ice-free rocks in the Southern Hemisphere is larger than in the Northern one. The tendency of similarity of latitudinal zonality observed both on the maps of the minimal and mean roof depths may be considered as an indicator of structural stability of upper horizons of the Martian cryolithosphere down to the depths of 300 to 400 m. The areas of minimal ice content in the nearsurface layers coincide with the zone of maximum thickness of ice-free rocks. The ice relative content in Martian rocks becomes systematically higher from 30 deg latitude to the polars. The same tendency is observed in depth. The data obtained may be useful for the selecting of landing sites for Mars samples return and other missions.

Kuzmin, R. O.↗