Geomorphic Degradations on the Surface of Venus: An Analysis of Venera 9 and Venera 10 Data

Abstract

On the basis of the physical and chemical measurements made on the surface of Venus and transmitted back to Earth by the Soviet automatic landers Venera 9 and Venera 10, a geomorphically inactive environment should be expected. An analysis of the television photographs reveals, however, that at least two processes of degradation occur. One operates on a scale of decimeters to meters and is responsible for the fracturing of a layered source rock and the subsequent downslope movement of the fragments. Mass-wasting, perhaps activated by venusian quakes or by unknown geological processes, is likely to be the agent. Another geomorphic degradation process occurs on the scale of a centimeter or less and is responsible for the rounding of edges and the pitting of rock surfaces. The agents of this process are not known, but atmospheric action, perhaps in connection with volcanic episodes, may be the cause. From a geomorphic point of view, the landscape of the Venera 9 landing site can be considered young and that of the Venera 10 landing site, mature.

Extraterrestrial dunes: An introduction to the special issue on planetary dune systems

“…The dense atmosphere includes a perpetual cloud cover that hides the entire surface of Venus from direct view from orbit, except through the use of radar. Lander images returned by Venera 8 and 9 (Florensky et al, 1977) and Venera 13 and 14 (Basilevsky et al, 1985;Head and Basilevsky, 1999) show that the surface of Venus includes an abundance of fine-grained particles capable of being moved by the wind, but no aeolian bedforms were imaged within the limited field of view available to the lander cameras. …”

Impact crater air fall deposits on the surface of Venus: Areal distribution, estimated thickness, recognition in surface panoramas, and implications for provenance of sampled surface materials

“…The geochemical measurements made by the Venera and Vega landers characterize the composition of the surface material down to the depths of a few centimeters (X‐ray fluorescence spectrometry) and several decimeters (gamma ray spectrometry) [ Surkov , 1997]. This material is represented by the described layered rocks and soil, the latter probably to a significant degree being the product of the degradation of the layered rocks [see, e.g., Florensky et al , 1977a, 1977b; Garvin et al , 1984; Basilevsky et al , 1985]. The results of the geochemical analyses were considered to be characteristics of the surface lavas composing the volcanic plains at the landing sites [e.g., Barsukov , 1992; Basilevsky et al , 1992, 1997; Head et al , 1992; Kargel et al , 1993; Grimm and Hess , 1997; DeShon et al , 2000; Abdrakhimov and Basilevsky , 2002].…”

“…Other potential sources of soil material could be ejecta from the smaller craters not forming parabolas as well as surface degradation of the layered rocks. [38] The erosion of the layered deposits is an observational fact [e.g., Florensky et al, 1977aFlorensky et al, , 1977bBasilevsky et al, 1985]. It is probably caused by winds (including normal ''meteorological'' winds), whose existence has been confirmed by direct observations [e.g., Selivanov et al, 1982;Ksanfomality et al, 1982;Ksanfomality, 1985;Kerzhanovich et al, 1982], and winds generated by nearby impacts [see, e.g., Ivanov, 1992], both large and forming radar-dark parabolic deposits, and smaller ones, forming parabola-free craters and splotches.…”

Aeolian processes on Venus

“…Soviet Venera images (Figure 2) of the surface show rock slabs, rock fragments several centimeters across, and crust-like soils, all of which could contribute sand and dust appropriate for aeolian activity (Florensky et al, 1977a(Florensky et al, ,b, 1983Basilevsky et al, 1985). Soil elemental abundances were measured using x-ray fluorescence at the Venera 13, 14 and Vega 2 sites.…”

“…Sagan (1973, Hess (1973, Iversen and White (1982), and Greeley et al (1984a) predicted the minimum winds required to entrain particles on Venus, based principally on theory or extrapolation from laboratory experiments performed under Venusian conditions. Venera lander spacecraft returned images of the surface that showed the presence of small grains and measured winds of sufficient strength to move them (Florensky et al, 1977a). Pioneer-Venus provided additional data on the atmosphere, including measurements of the winds (Counselman et al, 1979), as did the balloons inserted into the atmosphere during the Vega Mission (Blamont et al, 1986).…”