Venus

Venus in Color

The bluish hue of Venus is an effect of the colorization technique used to enhance subtle contrasts in cloud patterns and indicates that this image was taken through a violet filter. Features in the sulfuric acid clouds near the top of the planet's atmosphere are most prominent in violet and ultraviolet light. This image shows the east to west cloud banding and the brighter polar hoods . The features are embedded in winds that flow from east to west at about 370 kph (230 mph).

Impact Craters

Three large impact craters with diameters ranging from 37 km (23 mi) to 65 km (40 mi) are visible in the fractured plains. Features typical of meteorite impact craters are also visible. Rough radar-bright ejecta surrounds the perimeter of the craters; terraced inner walls and large central peaks can be seen. Crater floors appear dark because they are smooth and have been flooded by lava. Domes of probable volcanic origin can be seen in the southeastern corner. The domes range in diameter from 1-12 km (0.6-7 mi); some have central pits typical of volcanic shields or cones.

Bright Plains

Located along the left central edge of the image is a cluster of volcanic domes that ranges from 1.5 km (1 mi) to 7.5 km in diameter (5 mi). The domes and their deposits are located at the convergence of radar-bright lineaments that are interpreted to be faults and troughs. In some places the domes overlie the faults. The faults and troughs extend into the lower parts of the image where they terminate against dark plains deposits and are crosscut at right angles by additional faults. The relationship between these features indicates that multiple episodes of faulting and volcanism have occurred.

Ovda Regio

The tectonic fabric of this region of Ovda Regio trends predominantly east-west. The large radar-dark areas are probably tectonically formed basins that have been filled in by fluid lava flows, thus presenting a smooth surface to the Magellan radar system.

Ridges and Troughs

On this bright, lineated terrain Alpha Regio is a series of troughs, ridges, and faults running in every direction. The lengths of these features range from 10 km (6.3 mi) to 60 km (37 mi). The elevation of Alpha Regio varies over a range of 4 km (2.5 mi). Low-lying areas appear dark in the radar images and may be filled with lava. Volcanoes appear as bright spots on the smooth plains. Notice the large volcano in the upper right. At the center of this 35 km (22 mi) volcano is a caldera; its western edge appears to be either a debris flow or a lava flow. The black square represents missing data.

Highlands

Several tectonic events formed this complex terrain, which is part of the interior of Ovda Regio. An underlying fabric of ridges and valleys lies NE-SW. These ridges are spaced 10-20 km (6-12 mi) apart and may have been caused by compression of the crust at right angles to the ridge. The ridges are cut by bright features extending NW-SE. The largest valleys, particularly the 20 km (12 mi) wide valley extending across the image, were filled with dark material, probably lava. The complexity of Ovda Regio attests to a long history of tectonic deformation.

Eastern Lakshmi

Lava flows blanket the flat plains region of eastern Lakshmi. The dark flows most likely represent smooth flows similar to pahoehoe flows on Earth, while the brighter areas are rougher flows resembling Earth's aa flows. Three dark splotches mark the tops of these lava flows. Because of the thick atmosphere surrounding Venus, small impactors break up before they hit the surface. The fragments are deposited over the surface and produce the dark splotches seen here. Notice the splotch on the far right has a crater at its center, indicating that the impactor was not completely destroyed.

Lava flows

This mosaic highlights a system of east-trending, radar-bright and dark lava flows that collide with and breach a north-trending ridge belt (left of center). Upon breaching the ridge belt, the lava pooled, forming a radar-bright deposit approximately 100,000 square km (right side of image). The source of the lava is the Corona Derceto, which lies about 300 km (186 mi) west of the scene. The bright and dark bars extending from top to bottom are artifacts of image processing.

Coronas in Fortuna

Two large oval features can be seen in this image of Fortuna. On the left is Ba'het Patera, 230 km (138 mi) long and 150 km (90 mi) across. A portion of Onatah Corona, over 350 km (210 mi) in diameter, is visible on the right. Both features are surrounded by a ring of ridges and troughs. The central areas of the coronae contain radial fractures as well as volcanic domes and flows. Coronae may form due to the upwelling of hot material from deep in the interior of Venus. These two coronae may have formed at the same time over a single upwelling. The black strip represents missing data.

Lavinia Region

The bright area running from the upper right to the lower left may be part of a belt of ridges formed by compression and thickening of the upper layers of the planet. The area between the ridges suggests flooding by lava flows. The varied textures of the lava can be seen in the mottled appearance of the plains, which have been cut by the ridges; brighter, rougher flows are also quite common. The lighter area in the lower right corner is the northern extension of Mylitta Fluctus. The black strip represents missing

Arachnoids

Named by the Soviets for their spider and cobweb-like appearance, arachnoids are one of the more remarkable features found on Venus. They are 50 to 230 km (30 to 138 mi) diameter circular structures, with a central volcanic feature surrounded by a complex network of fractures. Arachnoids are similar in form but generally smaller than coronae. The radar- bright lines extending for many kilometers beyond the arachnoids may have been caused by an upwelling of magma from the interior of Venus, which pushed up the surface to form cracks.

Selu Corona

Located in Lada Terra, Selu Corona measures 350 km (210 mi) in diameter. Coronae are circular to elliptical features marked by a ring of concentric ridges, and are thought to result from the flow of heat in the planet's interior. As hot material rises, it weakens the upper layers of the crust, causing the surface to dome upwards. Then as the region cools, the dome begins to subside. As the upper layers rise and fall, they are subjected to stresses that crack the surface, creating both circular and radial fractures. The black strips represent missing data.

Corona

This region, roughly 100 km (60 mi) on a side, shows a gigantic structure known as a corona. Such features are thought to be the result of hot rising bodies of magma that reach the crust, and cause it to partially melt and collapse, generating volcanic flows and fault patterns that radiate from the central structure. Magellan acquired this view of Venus during its first mapping cycle around the planet in 1990 and 1991.

Sacajawea Patera

Sacajawea Patera is a huge caldera located in western Ishtar Terra. It measures approximately 233 km (140 mi) wide at its base, 1-2 km (0.6 -1.2 mi) deep and 120 by 215 km (74 by 133 mi) in diameter. The caldera is bounded by a zone of graben and fault scarps. Extending up to 140 km (87 mi) in length from the southeast of Sacajawea is a system of linear structures thought to be a flanking rift zone along which the lateral injection and eruption of magma may have occurred.

Domical Hills

Seven circular domes can be seen on the eastern edge of Alpha Regio. They average 25 km (15 mi) in diameter with maximum heights of 750 m (2475 ft). Some scientists believe they are the result of eruptions of thick lava that flowed from a vent on level ground, resulting in an even lateral pattern of lava. The concentric and radial fracture pattern on the surface of the domes suggests that lava welled up inside the domes, causing the surface to stretch.

Ticks

Scientists nicknamed this type of volcano a tick. About 66 km (41 mi) across at the base, this volcano has a flat, concave summit 35 km (22 mi) in diameter. The sides of the volcano are characterized by radiating ridges and valleys. To the west, the rim of the volcano appears to have been breached by dark lava flows that emanated from a shallow summit pit (5.4 km/3.3 mi in diameter) and traveled west along a channel. The black square represents missing data.