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Head, James W., III

Publications and source records attributed to Head, James W., III.

38 records · Page 3

Vega landing sites - Venera 15/16 unit analogs from Pioneer Venus reflectivity and RMS slope data

Pioneer Venus radar data on surface properties have been used to compare the Vega spacecraft landing sites with the northern 1/4 of Venus mapped by the orbiters Venera 15 and 16. The regions surrounding both landing sites possess surface reflectivity and small-scale roughness properties most similar to those of mapped volcanoes and volcanic plains regions and different surface properties than those of mapped tectonic units. Regions analogous to the Vega 1 site are relatively rare, covering 2.8 percent of the mapped surface. Vega 2 analogs are much more common and cover 22.6 percent of the surface. Neither landing site is representative of the nearby highlands of Aphrodite, but the Vega 2 landing site is similar to much of the northern plains of Venus.

Bindschadler, Duane L.↗

Volcanic processes and landforms on Venus - Theory, predictions, and observations

The ascent and eruption of magma on Venus in the current Venusian environment is modeled, taking into account the influence of extreme surface temperatures and pressures. Comparison of present predictions with observations obtained from Pioneer Venus, Arecibo, and Venera data support a picture of regional pyroclastic deposits being very rare, magma contents not usually exceeding about 4 wt pct, and the atmospheric pressure having been about the same as the present value over a time period equivalent to the average age of the northern areas of the northern hemisphere. Data suggest that numerous eruptions had effusion rates exceeding common terrestrial rates, and that shield volcanoes are often wide, but are low relative to those on Mars and earth. Implications of the proposed Venusian reduction of the driving density contrast include dike intrusion being very common, and large minimum magma volumes being required to ensure surface eruptions.

Head, James W., III↗