Layered rocks in Terby Crater



Terby Crater is a 174-kilometre (108-mile) wide crater that sinks some 5 km (3 miles) into the Martian crust. It's located on the northern rim of the large Hellas impact basin in the southern hemisphere of Mars and holds a wide range of landforms.



The mesa of layered deposits imaged here is located in the north-central part of the crater's interior. Hydrated minerals, including hydrated sulphates and clays, have been detected in these layers, providing evidence that Terby and Hellas may once have held an enormous lake up to 3.6 km (2.2 miles) deep.



(Image: NASA/JPL/University of Arizona)

Pollack Crater's White Rock



First imaged by the Mariner 9 spacecraft in 1972, this enigmatic group of wind-eroded ridges covers 15 by 18 km (9 by 11 miles) of Pollack Crater's floor. The feature's higher reflectivity, or albedo - compared with the darker material on the crater's floor - makes it appear white. In reality, White Rock has a dull, reddish colour and is likely composed of accumulated dust and sand with some fine-grained olivine (a volcanic mineral that degrades easily in water), surrounded by basaltic sand.



(Image: NASA/JPL/University of Arizona)

Herschel Crater's dark dunes



These dark-toned, crescent-shaped dunes are located on the floor of Herschel Crater - a 300-km (186-mile) wide impact basin in the ancient, cratered southern highlands of Mars. Barchan, or crescent-shaped, dunes are formed by winds that blow mostly in one direction - the dunes' "horns" point downwind. In this case, the strongest winds blow roughly north to south.



Herschel's basaltic sand dunes appear to have a pitted and grooved texture, indicating that the dune sands may be cemented together, or lithified.



(Image: NASA/JPL/University of Arizona) Advertisement

Swirls of Rock in Candor Chasma



Candor Chasma is a deep, elongated, steep-sided depression some 813 km (505 miles) long. It is one of two large canyons that make up the northern end of the Valles Marineris canyon system - the solar system's grandest canyon. Horizontal layers of sand- and dust-sized particles have been folded to form intricate swirls and curves. The layers may have originally been laid down as sediments that accumulated in shallow lakes, since MRO's CRISM spectrometer has found hydrated sulphates in Candor. The sedimentary layers were probably deformed later and eroded, exposing the elaborate patterns we see today.



(Image: NASA/JPL/University of Arizona)