Martian Geological Features

High-resolution images from Mars showing volcanic pits and craters, revealing complex geological layers and dust patterns from impacts.

Although actively-forming gullies are common in the middle latitudes of Mars, there are also pristine-looking gullies in equatorial regions. In this scene, the gullies have very sharp channels and different colors where the gullies have eroded and deposited material. Over time, the topography becomes smoothed over and the color variations disappear, unless there is recent activity. Changes have not been visible here from before-and-after images, and maybe such differences are apparent compared to older images, but nobody has done a careful comparison. What may be needed to see subtle changes is a new image that matches the lighting conditions of an older one. Equatorial gully activity is probably much less common perhaps there is major downslope avalanching every few centuries so we need to be lucky to see changes. MRO has now been imaging Mars for over 16 years, and the chance of seeing rare activity increases as the time interval widens between repeat images.

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This observance from NASA's Mars Reconnaissance Orbiter covers a pit in the lower West flank of Arsia Mons, one of the four giant volcanos of the Tharsis region. Many layers are exposed in the pit, probably marking individual lava flows.

$This image was acquired on April 8, 2018 by NASA's Mars Reconnaissance Orbiter. This image shows the gullied western slopes of an unnamed crater (about 10 kilometers wide) in Acidalia Planitia. These slopes have gone through a complicated history of gully erosion of the bedrock layers in the upper section, followed by the formation of fractures along the lower slopes. As the gullies continued to form, fractures cut across them and their debris fans in the lower part of the slopes. A prominent cliff has been eroded by more recent gully activity. The curved ridges and lobes on the crater floor, downslope of the debris fans, along with multiple fractures, suggest that the subsurface was ice-rich. This is an example of how geologists can utilize the concept of superposition to unravel the relative timing of geological events in the crater's history. More information is available at$

$Tectonic fractures within the Candor Chasma region of Valles Marineris, Mars, retain ridge-like shapes as the surrounding bedrock erodes away$

$view from the Mast Camera (Mastcam) on NASA's Curiosity Mars rover, showing a network of two-tone mineral veins at an area called 'Garden City' on lower Mount Sharp. Mineral veins such as these form where fluids move through fractured rocks, depositing minerals in the fractures and affecting chemistry of the surrounding rock. In this case, the veins have been more resistant to erosion than the surrounding host rock.$

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$Sapas Mons is displayed in the centre of this computer-generated three-dimensional perspective view of the surface of Venus. The viewpoint is located 527 kilometres (327 miles) northwest of Sapas Mons at an elevation of 4 kilometres (2.5 miles) above the terrain. Lava flows extend for hundreds of kilometres across the fractured plains shown in the foreground to the base of Sapas Mons. The view is to the southeast with Sapas Mons appearing at the centre with Maat Mons located in the background on the horizon. Sapas Mons, a volcano 400 kilometres (248 miles) across and 1.5 kilometres (0.9 mile) high is located at approximately 8 degrees north latitude, 188 degrees east longitude, on the western edge of Atla Regio. Its peak sits at an elevation of 4.5 kilometres (2.8 miles) above the planets mean elevation. Sapas Mons is named for a Phoenician goddess$

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