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The surface of Venus.
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| THE SURFACE OF VENUS | |||
| The Russian probes that landed on the surface returned several views of the surface of Venus. They showed flat slabs of rock, with loose stones and dark sandy material, as seen above. These pictures and the chemical analysis they carried out confirmed the volcanic nature of the Venusian plains. | |||
| At Beta Regio (a large elevated region), Venera 10 determined the materials to be basaltic, fine grained volcanic rocks, containing a little more potassium, thorium and uranium than the basalts found on Earth. Landing near Phoebe Regio, Venera 13, reported potassium rich basalts, while 900 kilometres further to the southeast, the rocks at the Venera 14 landing site were close in composition to the basalts found on Earth's sea floor. | |||
Phoebe
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| Venus is fairly flat and has no continents or ocean basins. The subdued topography is often described as gently rolling plains. | |||
 The picture shown here is a computer-generated view of the volcanic plains surrounding Gula Mons. |
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Gula Mons |
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| Volcanism | |||
| Volcanism has dominated the geological history of Venus. Large volcanic outpourings, with no obvious source, cover much of the planet, flooding low-lying regions and partially burying features at higher elevations. Volcanic plains account for the subdued landscape. Elevated terrain and complex intertwining ridge belts, formed through compression and buckling of the surface, segregate the plains regions. | |||
| Venus has numerous volcanoes, like Sapas Mons shown here, with a wide variety of structures and a large range of sizes. | |||
| More about Venusian volcanoes | |||
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Sapas Mons |
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| Highlands | |||
| Though much of Venus is very flat, there are several highland regions. The main ones are Ishtar Terra and Aphrodite Terra. | |||
| Ishtar, in the northern hemisphere, is about the size of Australia and contains the large plateau Lakshmi, rising 4 kilometres above the surrounding area. | |||
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Lakshmi Planum |
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 To the east of Lakshmi is Venus' highest mountain, Maxwell Montes, rising to a height of 12 kilometres Shown here are Maxwell Montes and the impact crater Cleopatra. |
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Maxwell Montes |
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| Aphrodite Terra | |||
| Aphrodite Terra, a scorpion shaped landmass, dominates the equatorial region for half the planet's circumference. Aphrodite encompasses various types of terrain, including the highly deformed crustal blocks of Ovda and Thetis Regio which make up most of its elevated regions. Aphrodite also incorporates ridge belts, and chasmata to the east, including Ganis, Dali and Diana Chasma which have some of the most extreme topography on the planet. | |||
| Fractures | |||
| Criss-crossing the plains of Venus are many types of fractures, some are arranged in a grid-like pattern. Such grid networks are thought to have formed by extension of the surface, as it is pulled in different directions. | |||
 Other fracture patterns are more irregular and have an almost random appearance. One of the most common types of faulting occurring in the plains are wrinkle ridges. These are raised irregular ridges thought to have been produced by compression. |
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| Tesserae | |||
| Although most of the surface is fairly smooth, probably like the terrain imaged by the Venera landers, there are large upland regions which are extremely rugged. These regions, known as tesserae, have a rough surface, and are very bright in radar images. One of the main characteristics of tesserae are their complex ridges and groove patterns, which are considered to have formed through repeated extension and compression of the surface. | |||
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