Venus surface features

Arguments in favor of carbonates include the following. Some of the flow features on Venus surface look like they were made by magmas, such as carbonatites, with water-Uke rheologies. If correct, these geomorphological interpretations... 

Interference from the Earth s atmosphere has always been a problem for optical astronomers, especially when attempting to view surface details on the terrestrial planets such as Mercury or Mars. Planets with dense atmospheres such as Venus also present a problem for astronomers because their thick cloud layers prevent direct surface observations. To overcome this difficulty, in the 1950 s, astronomers developed a technique using radar imaging to reveal surface features. Radar signals can easily penetrate clouds and are reflected back by items they hit. By... 

There are three planets other than Earth in the inner solar system. The innermost is Mercury tiny, barren, and hard to observe as it is located near the Sun. Next comes Venus, the planet nearest in size and mass to Earth, but swathed in clouds a bland, featureless ball through the small telescope. Mars, half again as far from the Sun as Earth, is different. Features are distinguishable on its surface, and it sometimes shows polar ice caps that look much like Earth s. 

The surface of Venus has K/U ratios of the same order as those of terrestrial surface rocks (Surkov 1981), so that it also is depleted in volatile elements relative to primitive nebula values. This relative depletion of the more volatile elements thus appears to have been a widespread feature of the inner solar nebula rather than being a feature unique to the earth. Accordingly, a widespread loss of volatile elements occurred in the irmer solar system prior to the accretion of the terrestrial planets (Taylor 1987a). No information is yet available for the rare earth elements on Venus, but on the basis of the discussion above, they are probably similar to the terrestrial abundance levels. 

Diffuse scattering from Mars is much more substantial than for the other quasispecular targets and often accounts for most of the echo power, so the average near-surface abundance of centimeter-to-meter-scale rocks presumably is much greater on Mars than on the Moon, Mercury, or Venus. Features in Mars SC spectra first revealed the existence of regions of extremely small-scale roughness (see... 

Water vapor is an important trace gas in the lower Venus atmosphere and it contributes to the global greenhouse effect that maintains the high surface temperature. Most of the H2O is found below the cloud base at about 47 km. Its signature can be observed in a spectral window between 0.9 and 2.5 pm where the atmospheric absorption is weak, therefore H2O absorption features can be seen. For H2O abundance determinations the following windows are most often used 1.18, 1.74 and 2.3 pm. 

As we have already pointed out, comets may have been very important for the Earth and terrestrial planets because they deposited during collisions considerable amounts of water on the surfaces of these planets. On March 18, 1988 dark features on nine consecutive photographs were observed on Venus. Since film defects and other interferences (e.g. from an artificial Earth satellite or interplanetary object) can be ruled out, it is highly probable that this event was an impact of a small cometary like object that took place on the upper haze layer of the dense Venusian atmosphere. Because such an object consists mainly of water, evaporation of H2SO4 particles occurred which decreased the albedo at the point of entrance and therefore a dark feature appeared (Kolovos, Varvoglis and Pylarinou, 1991 [189]). 

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