Inverted relief, inverted topography, or topographic inversion refers to landscape features that have reversed their elevation relative to other features. It most often occurs when low areas of a landscape become filled with lava or sediment that hardens into material that is more resistant to erosion than the material that surrounds it. Differential erosion then removes the less resistant surrounding material, leaving behind the younger resistant material, which may then appear as a ridge where previously there was a valley. Terms such as "inverted valley" or "inverted channel" are used to describe such features. [1] Inverted relief has been observed on the surfaces of other planets as well as on Earth. For example, well-documented inverted topographies have been discovered on Mars. [2]
Several processes can cause the floor of a depression to become more resistant to erosion than its surrounding slopes and uplands:
A classic example of inverted relief is Table Mountain, Tuolumne County, California. Multiple lava flows filled an ancient fluvial valley that cut westward through the central Sierra Nevada range to the Central Valley about 10.5 million years ago. These Miocene lava flows filled this ancient river valley with a thick sequence of potassium-rich trachyandesite lavas that are significantly more resistant to erosion than the Mesozoic siltstone and other rock in which the valley was cut. Thus, subsequent differential erosion left these volcanic rocks as a sinuous ridge, which now stands well above landscape underlain by more deeply eroded Mesozoic rocks. [5]
Another example is Table Mountain, Cape Town, where the original high ridges of resistant quartzitic sandstone of the Cape Fold Belt were eroded away first, exposing less resistant rock, which eroded faster, leaving the original valley bottom at the top of the residual mountain. [4]
Inverted relief in the form of sinuous and meandering ridges, which are indicative of ancient, inverted fluvial channels, is argued to be evidence of water channels on the Martian surface in the past. [6] [7] [8] [2] [9] [10] An example is Miyamoto Crater, which was proposed in 2010 as a potential location to be searched for evidence of life on Mars. [11]
Other examples are shown in the photographs below.
Amazonis Planitia is one of the smoothest plains on Mars. It is located between the Tharsis and Elysium volcanic provinces, to the west of Olympus Mons, in the Amazonis and Memnonia quadrangles, centered at 24.8°N 196.0°E. The plain's topography exhibits extremely smooth features at several different lengths of scale. A large part of the Medusae Fossae Formation lies in Amazonis Planitia.
Terra Sirenum is a large region in the southern hemisphere of the planet Mars. It is centered at 39.7°S 150°W and covers 3900 km at its broadest extent. It covers latitudes 10 to 70 South and longitudes 110 to 180 W. Terra Sirenum is an upland area notable for massive cratering including the large Newton Crater. Terra Sirenum is in the Phaethontis quadrangle and the Memnonia quadrangle of Mars. A low area in Terra Sirenum is believed to have once held a lake that eventually drained through Ma'adim Vallis.
Tempe Terra is a heavily cratered highland region in the northern hemisphere of the planet Mars. Located at the northeastern edge of the Tharsis volcanic province, Tempe Terra is notable for its high degree of crustal fracturing and deformation. The region also contains many small shield volcanoes, lava flows, and other volcanic structures.
The geology of Mars is the scientific study of the surface, crust, and interior of the planet Mars. It emphasizes the composition, structure, history, and physical processes that shape the planet. It is analogous to the field of terrestrial geology. In planetary science, the term geology is used in its broadest sense to mean the study of the solid parts of planets and moons. The term incorporates aspects of geophysics, geochemistry, mineralogy, geodesy, and cartography. A neologism, areology, from the Greek word Arēs (Mars), sometimes appears as a synonym for Mars's geology in the popular media and works of science fiction. The term areology is also used by the Areological Society.
Antoniadi is a crater on Syrtis Major Planum in the Syrtis Major quadrangle, Mars, located at 21.5° north latitude and 299.2° west longitude. It is 394 km (245 mi) long and was named after Eugène Michael Antoniadi, a Greek astronomer (1870–1944) who spent most of his life in France.
Juventae Chasma is an enormous box canyon on Mars which opens to the north and forms the outflow channel Maja Valles. Juventae Chasma is located north of Valles Marineris in the Coprates quadrangle and cuts more than 5 km into the plains of Lunae Planum.
Melas Chasma 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.
Miyamoto is a crater within the Margaritifer Sinus quadrangle (MC-19) region of the planet Mars, west of the Plains of Meridiani. It is 150 kilometers (93 mi) wide. Its northeastern half is filled with rocks formed in the presence of water and include minerals of iron and sulfur, which likely settled on lake bottoms or in groundwater systems. In the southwestern half of the crater floor, erosion has stripped these materials away, revealing clays and other materials like those found in the most ancient Martian rocks. More than 3.5 billion years old, they date to the Noachian era at which time, liquid water was likely present at the surface and could have created an environment favorable to life.
The Medusae Fossae Formation is a large geological formation of probable volcanic origin on the planet Mars. It is named for the Medusa of Greek mythology. "Fossae" is Latin for "trenches". The formation is a collection of soft, easily eroded deposits that extends discontinuously for more than 5,000 km along the equator of Mars. Its roughly-shaped regions extend from just south of Olympus Mons to Apollinaris Patera, with a smaller additional region closer to Gale Crater.
The Diacria quadrangle is one of a series of 30 quadrangle maps of Mars used by the United States Geological Survey (USGS) Astrogeology Research Program. The quadrangle is located in the northwestern portion of Mars' western hemisphere and covers 180° to 240° east longitude and 30° to 65° north latitude. The quadrangle uses a Lambert conformal conic projection at a nominal scale of 1:5,000,000 (1:5M). The Diacria quadrangle is also referred to as MC-2. The Diacria quadrangle covers parts of Arcadia Planitia and Amazonis Planitia.
The Syrtis Major quadrangle is one of a series of 30 quadrangle maps of Mars used by the United States Geological Survey (USGS) Astrogeology Research Program. The Syrtis Major quadrangle is also referred to as MC-13.
The Amazonis quadrangle is one of a series of 30 quadrangle maps of Mars used by the United States Geological Survey (USGS) Astrogeology Research Program. The Amazonis quadrangle is also referred to as MC-8.
The Oxia Palus quadrangle is one of a series of 30 quadrangle maps of Mars used by the United States Geological Survey (USGS) Astrogeology Research Program. The Oxia Palus quadrangle is also referred to as MC-11.
The Coprates quadrangle is one of a series of 30 quadrangle maps of Mars used by the United States Geological Survey (USGS) Astrogeology Research Program. The Coprates quadrangle is also referred to as MC-18. The Coprates quadrangle contains parts of many of the old classical regions of Mars: Sinai Planum, Solis Planum, Thaumasia Planum, Lunae Planum, Noachis Terra, and Xanthe Terra.
The Margaritifer Sinus quadrangle is one of a series of 30 quadrangle maps of Mars used by the United States Geological Survey (USGS) Astrogeology Research Program. The Margaritifer Sinus quadrangle is also referred to as MC-19. The Margaritifer Sinus quadrangle covers the area from 0° to 45° west longitude and 0° to 30° south latitude on Mars. Margaritifer Sinus quadrangle contains Margaritifer Terra and parts of Xanthe Terra, Noachis Terra, Arabia Terra, and Meridiani Planum.
The Maja Valles are a large system of ancient outflow channels in the Lunae Palus quadrangle on Mars. Their location is 12.6° north latitude and 58.3° west longitude. The name is a Nepali word for "Mars". The Maja Valles begin at Juventae Chasma. Parts of the system have been partially buried by thin volcanic debris. The channels end at Chryse Planitia.
To date, interplanetary spacecraft have provided abundant evidence of water on Mars, dating back to the Mariner 9 mission, which arrived at Mars in 1971. This article provides a mission by mission breakdown of the discoveries they have made. For a more comprehensive description of evidence for water on Mars today, and the history of water on that planet, see Water on Mars.
The Mars Reconnaissance Orbiter's HiRISE instrument has taken many images that strongly suggest that Mars has had a rich history of water-related processes. Many features of Mars appear to be created by large amounts of water. That Mars once possessed large amounts of water was confirmed by isotope studies in a study published in March 2015, by a team of scientists showing that the ice caps were highly enriched with deuterium, heavy hydrogen, by seven times as much as the Earth. This means that Mars has lost a volume of water 6.5 times what is stored in today's polar caps. The water for a time would have formed an ocean in the low-lying Mare Boreum. The amount of water could have covered the planet about 140 meters, but was probably in an ocean that in places would be almost 1 mile deep.
Rain and snow was a regular occurrence on Mars in the past; especially in the Noachian and early Hesperian epochs. Water was theorized to seep into the ground until it reached a formation that would not allow it to penetrate further. Water then accumulated forming a saturated layer. Deep aquifers may still exist.
The common surface features of Mars include dark slope streaks, dust devil tracks, sand dunes, Medusae Fossae Formation, fretted terrain, layers, gullies, glaciers, scalloped topography, chaos terrain, possible ancient rivers, pedestal craters, brain terrain, and ring mold craters.