Mars Reconnaissance Orbiter in the context of Aerobraking

A Mars rover is a remote-controlled motor vehicle designed to travel on the surface of Mars. Rovers have several advantages over stationary landers: they examine more territory, they can be directed to interesting features, they can place themselves in sunny positions to weather winter months, and they can advance the knowledge of how to perform very remote robotic vehicle control. They serve a different purpose than orbital spacecraft like Mars Reconnaissance Orbiter. A more recent development is the Mars helicopter.

As of May 2021, there have been six successful robotically operated Mars rovers; the first five, managed by the American NASA Jet Propulsion Laboratory, were (by date of Mars landing): Sojourner (1997), Spirit (2004–2010), Opportunity (2004–2018), Curiosity (2012–present), and Perseverance (2021–present). The sixth, managed by the China National Space Administration, is Zhurong (2021–2022).

SHARAD (Mars SHAllow RADar sounder) is a subsurface sounding radar embarked on the Mars Reconnaissance Orbiter (MRO) probe. It complements the MARSIS radar on Mars Express orbiter, providing lower penetration capabilities (some hundred meters) but much finer resolution of 15 meters in free space.

SHARAD was developed under the responsibility of the Italian Space Agency (ASI, Agenzia Spaziale Italiana), and provided to JPL for use on board NASA's Mars Reconnaissance Orbiter spacecraft in the frame of a NASA/ASI agreement which foresees exploitation of the data by a joint Italian/US team. The INFOCOM dept. of the University of Sapienza University of Rome is responsible for the instrument operations, while Thales Alenia Space Italia (formerly Alenia Spazio) designed and built the instruments. SHARAD operations are managed by INFOCOM from the SHARAD Operation Centre (SHOC), located within the Alcatel Alenia Space facilities in the suburbs of Rome.

Fretted terrain is a type of surface feature common to certain areas of Mars and was discovered in Mariner 9 images. It lies between two different types of terrain. The surface of Mars can be divided into two parts: low, young, uncratered plains that cover most of the northern hemisphere, and high-standing, old, heavily cratered areas that cover the southern and a small part of the northern hemisphere. Between these two zones is a region called the Martian dichotomy and parts of it contain fretted terrain. This terrain contains a complicated mix of cliffs, mesas, buttes, and straight-walled and sinuous canyons. It contains smooth, flat lowlands along with steep cliffs. The scarps or cliffs are usually 1 to 2 km high. Channels in the area have wide, flat floors and steep walls. Fretted terrain shows up in northern Arabia, between latitudes 30°N and 50°N and longitudes 270°W and 360°W, and in Aeolis Mensae, between 10 N and 10 S latitude and 240 W and 210 W longitude. Two good examples of fretted terrain are Deuteronilus Mensae and Protonilus Mensae.

Fretted terrain in Arabia Terra (Ismenius Lacus quadrangle), seems to transition from narrow straight valleys to isolated mesas. Most of the mesas are surrounded by forms that have been given a variety of names: circum-mesa aprons, debris aprons, rock glaciers, and lobate debris aprons. At first, they appeared to resemble rock glaciers on Earth. Even after the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) took a variety of pictures of fretted terrain, experts could not tell for sure if material was moving or flowing as it would in an ice-rich deposit (glacier). Eventually, proof of their true nature was discovered when radar studies with the Mars Reconnaissance Orbiter showed that they contained pure water ice covered with a thin layer of rocks that insulated the ice.

Lobate debris aprons (LDAs) are geological features on Mars, first seen by the Viking Orbiters, consisting of piles of rock debris below cliffs. These features have a convex topography and a gentle slope from cliffs or escarpments, which suggest flow away from the steep source cliff. In addition, lobate debris aprons can show surface lineations as do rock glaciers on the Earth.

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  Wide view of mesa with CTX showing cliff face and location of lobate debris apron (LDA) Location is Ismenius Lacus quadrangle.
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  Enlargement of previous CTX image of mesa. This image shows the cliff face and detail in the LDA. Image taken with HiRISE under HiWish program. Location is Ismenius Lacus quadrangle.
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  Lobate debris aprons (LDAs) around a mesa, as seen by CTX. Mesa and LDAs are labeled, so one can see their relationship. Radar studies have determined that LDAs contain ice; therefore, these can be important for future colonists of Mars. Location is Ismenius Lacus quadrangle.
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  Close-up of lobate debris apron (LDA), as seen by HiRISE under HiWish program
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  Lobate debris apron in Phlegra Montes, as seen by HiRISE. The debris apron is probably mostly ice with a thin covering of rock debris, so it could be a useful source of water. Scale bar is 500 meters (1,600 feet) long.
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  Close-up of surface of a lobate debris apron in Hellas quadrangle. Note the lines that are common in rock glaciers on the Earth.
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  Place where a lobate debris apron begins. Note stripes which indicate movement. Image located in Ismenius Lacus quadrangle.

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  Wide view of mesa with surrounding lobate debris apron, as seen by CTX. Part of this picture is enlarged in the following HiRISE image. Location is the Ismenius Lacus quadrangle.
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  Part of lobate debris apron, as seen by HiRISE under HiWish program This lobate debris apron surrounds a mesa. Location is the Ismenius Lacus quadrangle.
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  Lobate debris apron around mesa, as seen by HiRISE under HiWish program
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  Close view of lobate debris apron around mesa, as seen by HiRISE under HiWish program. Brain terrain is visible.

The Mars Reconnaissance Orbiter's Shallow Radar gave a strong reflection from the top and base of LDAs, meaning that pure water ice made up the bulk of the formation (between the two reflections). This is evidence that the LDAs in Hellas Planitia are glaciers covered with a thin layer of rocks. In addition, radar studies in Deuteronilus Mensae show that all lobate debris aprons examined in that region contain ice.

Rock glaciers are distinctive geomorphological landforms that consist either of angular rock debris frozen in interstitial ice, former "true" glaciers overlain by a layer of talus, or something in between. Rock glaciers are normally found at high latitudes and/or elevations, and may extend outward and downslope from talus cones, glaciers or terminal moraines of glaciers. The early textbook 'Characteristics of Existing Glaciers' refers to the varied, sometimes confusing, names given to these features; 'stone rivers', 'rock flows', 'rock streams' and 'rock glaciers', and includes a map and two photographs of 'rock streams' from the Silverton area of Colorado from the US Geological Surveyors Ernest Howe and W Cross. About the same time, Stephen Capps was surveying in the Wrangell Mountains, Alaska and reported similar landforms in the McCarthy area. Although a variety of names seemed to have be used in the USGS at this time, it is 'rock glacier' that is now generally used.

There are two models of rock glacier formation and flow: permafrost rock glaciers (sometimes termed talus-derived rock glaciers), and glacial rock glaciers, such as the Timpanogos Glacier [40.3847,-111.6415] in Utah, which may be found where glaciers once existed. A rock glacier has formed with rock debris covering a small glacier on Mt. St. Helens [46.2074,-122.1838]. Possible Martian rock glacier features have been identified by the Mars Reconnaissance Orbiter spacecraft. A rock glacier, especially if its origin is unclear, can be considered as a discrete debris accumulation. Rock avalanches can be misidentified as rock glaciers, or may evolve into them.

Melas Chasma /ˈmiːləs ˈkæzmə/ is a canyon on Mars, the widest segment of the Valles Marineris canyon system, located east of Ius Chasma at 9.8°S, 283.6°E in Coprates quadrangle. It cuts through layered deposits that are thought to be sediments from an old lake that resulted from runoff of the valley networks to the west. Other theories include windblown sediment deposits and volcanic ash. Support for abundant, past water in Melas Chasma is the discovery by MRO of hydrated sulfates. In addition, sulfate and iron oxides were found by the same satellite. Although not chosen as one of the finalists, it was one of eight potential landing sites for the Mars 2020 rover, a mission with a focus on astrobiology.

The floor of Melas Chasma is about 70% younger massive material that is thought to be volcanic ash whipped up by the wind into eolian features. It also contains rough floor material from the erosion of the canyon walls. Around the edges of Melas is also much slide material.

Candor Chasma is one of the largest canyons in the Valles Marineris canyon system on Mars. The feature is geographically divided into two halves: East and West Candor Chasmas, respectively. It is unclear how the canyon originally formed; one theory is that it was expanded and deepened by tectonic processes similar to a graben, while another suggests that it was formed by subsurface water erosion similar to a karst. MRO discovered sulfates, hydrated sulfates, and iron oxides in Candor Chasma.

One of the pictures below shows branched channels. Many places on Mars show channels of different sizes. Many of these channels probably carried water, at least for a time. The climate of Mars may have been such in the past that water ran on its surface. It has been known for some time that Mars undergoes many large changes in its tilt or obliquity because its two small moons lack the gravity to stabilize it, as the Moon stabilizes Earth; at times the tilt of Mars has even been greater than 80 degrees

Eos Chasma is a chasma in the southern part of the Valles Marineris canyon system of the Coprates quadrangle and the Margaritifer Sinus quadrangles of the planet Mars.

Eos Chasma’s western floor is mainly composed of an etched massive material composed of either volcanic or eolian deposits later eroded by the Martian wind. The eastern end of the Eos chasma has a large area of streamlined bars and longitudinal striations. This is interpreted to be stream-carved plateau deposits and material transported and deposited by flowing fluid. Ganges Chasma is an offshoot of Eos Chasma. MRO discovered sulfate, hydrated sulfate, and iron oxides in Eos Chasma.