Maxwell Montes is a mountain range on the planet Venus, of which Skadi Mons is the highest.
The geology of Venus is the scientific study of the surface, crust, and interior of the planet Venus. Within the Solar System, it is the one nearest to Earth and most like it in terms of mass, but has no magnetic field or recognizable plate tectonic system. Much of the ground surface is exposed volcanic bedrock, some with thin and patchy layers of soil covering, in marked contrast with Earth, the Moon, and Mars. Some impact craters are present, but Venus is similar to Earth in that there are fewer craters than on the other rocky planets that are largely covered by them. This is due in part to the thickness of the Venusian atmosphere disrupting small impactors before they strike the ground, but the paucity of large craters may be due to volcanic re-surfacing, possibly of a catastrophic nature. Volcanism appears to be the dominant agent of geological change on Venus. Some of the volcanic landforms appear to be unique to the planet. There are shield and composite volcanoes similar to those found on Earth, although these volcanoes are significantly shorter than those found on Earth or Mars. Given that Venus has approximately the same size, density, and composition as Earth, it is plausible that volcanism may be continuing on the planet today, as demonstrated by recent studies.
Cleopatra is an impact crater on Venus, in Maxwell Montes. Cleopatra is a double-ring impact basin about 100 kilometers (62 mi) in diameter and 2.5 kilometers (1.6 mi) deep. A steep-walled, winding channel a few kilometers wide breaks through the rough terrain surrounding the crater rim. A large amount of lava originating in Cleopatra flowed through this channel and filled valleys in Fortuna Tessera. Cleopatra is superimposed on the structures of Maxwell Montes and appears to be undeformed, indicating that Cleopatra is relatively young. The crater is named after Egyptian queen Cleopatra VII.
Baltis Vallis is a sinuous channel on Venus ranging from 1–3 km (0.62–1.86 mi) wide and ~6,800 km (4,200 mi) long, slightly longer than the Nile and the longest known channel of any kind in the Solar System. It is thought the channel once held a river of lava. It is a single channel over most of its length, but anastomoses in several sections, for lengths of up to 400 km (250 mi). There appear to be other, smaller channels in the same area, down to the limit of resolution, some of which seem to be tributaries of Baltis Vallis.
The Victoria quadrangle is a region on Mercury from 0 to 90° longitude and 20 to 70 ° latitude. It is designated the "H-2" quadrangle, and is also known as Aurora after a large albedo feature.
The Tolstoj quadrangle in the equatorial region of Mercury runs from 144 to 216° longitude and -25 to 25° latitude. It was provisionally called "Tir", but renamed after Leo Tolstoy by the International Astronomical Union in 1976. Also called Phaethontias.
The Michelangelo quadrangle is in the southern hemisphere of the planet Mercury, where the imaged part is heavily cratered terrain that has been strongly influenced by the presence of multiring basins. At least four such basins, now nearly obliterated, have largely controlled the distribution of plains materials and structural trends in the map area. Many craters, interpreted to be of impact origin, display a spectrum of modification styles and degradation states. The interaction between basins, craters, and plains in this quadrangle provides important clues to geologic processes that have formed the morphology of the mercurian surface.
Ovda Regio is a Venusian crustal plateau located near the equator in the western highland region of Aphrodite Terra that stretches from 10°N to 15°S and 50°E to 110°E. Known as the largest crustal plateau in Venus, the regio covers an area of approximately 15,000,000 square kilometres (5,800,000 sq mi) and is bounded by regional plains to the north, Salus Tessera to the west, Thetis Regio to the east, and Kuanja as well as Ix Chel chasmata to the south. The crustal plateau serves as a place to hold the localized tessera terrains in the planet, which makes up roughly 8% of Venus' surface area. The kinematic evolution of crustal plateaus on Venus has been a debated topic in the planetary science community. Understanding its complex evolution is expected to contribute to a better knowledge of the geodynamic history of Venus. It is named after a Marijian forest spirit that can appear as both male and female.
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.
Glaciers, loosely defined as patches of currently or recently flowing ice, are thought to be present across large but restricted areas of the modern Martian surface, and are inferred to have been more widely distributed at times in the past. Lobate convex features on the surface known as viscous flow features and lobate debris aprons, which show the characteristics of non-Newtonian flow, are now almost unanimously regarded as true glaciers.
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.
Brain terrain, also called knobs-brain coral and brain coral terrain, is a feature of the Martian surface, consisting of complex ridges found on lobate debris aprons, lineated valley fill and concentric crater fill. It is so named because it suggests the ridges on the surface of the human brain. Wide ridges are called closed-cell brain terrain, and the less common narrow ridges are called open-cell brain terrain. It is thought that the wide closed-cell terrain contains a core of ice, and when the ice disappears the center of the wide ridge collapses to produce the narrow ridges of the open-cell brain terrain. Shadow measurements from HiRISE indicate the ridges are 4-5 meters high. Brain terrain has been observed to form from what has been called an "Upper Plains Unit." The process begins with the formation of stress cracks. The upper plains unit fell from the sky as snow and as ice coated dust.
Guinevere Planitia is an expansive lowland region of Venus that lies east of Beta Regio and west of Eistla Regio. These low-lying plains, particularly in the western portion, are characterized by apparent volcanic source vents and broad regions of bright, dark, and mottled deposits. They are the only break in an equatorially connected zone of highlands and tectonic zones. The types, numbers, and patterns of mapped tectonic features and small volcanic landforms in the region provide important detail in the interpretation and evolution of venusian landscape.
NASA's Magellan spacecraft mission discovered that Venus has a geologically young surface with a relatively uniform age of 500±200 Ma. The age of Venus was revealed by the observation of over 900 impact craters on the surface of the planet. These impact craters are nearly uniformly distributed over the surface of Venus and less than 10% have been modified by plains of volcanism or deformation. These observations indicate that a catastrophic resurfacing event took place on Venus around 500 Ma, and was followed by a dramatic decline in resurfacing rate. The radar images from the Magellan missions revealed that the terrestrial style of plate tectonics is not active on Venus and the surface currently appears to be immobile.
Irnini Mons is a volcanic structure on the planet Venus, and is named after the Assyro-Babylonian goddess of cedar-tree mountains. It has a diameter of 475 km (295 mi), a height of 1.75 km (1.09 mi), and is located in Venus' northern hemisphere. More specifically, it is located in the central Eistla Regio region at in the V-20 quadrangle. Sappho Patera, a 225 km (140 mi) diameter wide, caldera-like, depression tops the summit of Irnini Mons. The primary structural features surrounding Irnini Mons are graben, seen as linear depressed sections of rock, radiating from the central magma chamber. Also, concentric, circular ridges and graben outline the Sappho Patera depression at the summit. The volcano is crossed by various rift zones, including the north-south trending Badb Linea rift, the Guor Linea rift extending to the northwest, and the Virtus Linea rift continuing to the southeast.
A tessera is a region of heavily deformed terrain on Venus, characterized by two or more intersecting tectonic elements, high topography, and subsequent high radar backscatter. Tesserae often represent the oldest material at any given location and are among the most tectonically deformed terrains on Venus's surface. Diverse types of tessera terrain exist. It is not currently clear if this is due to a variety in the interactions of Venus's mantle with regional crustal or lithospheric stresses, or if these diverse terrains represent different locations in the timeline of crustal plateau formation and fall. Multiple models of tessera formation exist and further extensive studies of Venus's surface are necessary to fully understand this complex terrain.
Lada Terra, named for a Slavic goddess of Love, is a major landmass near the south pole of Venus which is centered at 60°S and 20°E and has a diameter of 8,615 kilometres (5,353 mi). It is defined by the International Astronomical Union as one of the three "major landmasses," or terrae, of Venus. The term "landmass" is not analogous to the landmass on Earth, as there are no apparent oceans on Venus. The term here applies to a substantial portion of land that lies above the average planetary radius, and corresponds to highlands.
The surface of Venus is dominated by geologic features that include volcanoes, large impact craters, and aeolian erosion and sedimentation landforms. Venus has a topography reflecting its single, strong crustal plate, with a unimodal elevation distribution that preserves geologic structures for long periods of time. Studies of the Venusian surface are based on imaging, radar, and altimetry data collected from several exploratory space probes, particularly Magellan, since 1961. Despite its similarities to Earth in size, mass, density, and possibly composition, Venus has a unique geology that is unlike Earth's. Although much older than Earth's, the surface of Venus is relatively young compared to other terrestrial planets, possibly due to a global-scale resurfacing event that buried much of the previous rock record. Venus is believed to have approximately the same bulk elemental composition as Earth, due to the physical similarities, but the exact composition is unknown. The surface conditions on Venus are more extreme than on Earth, with temperatures ranging from 453 to 473 °C and pressures of 95 bar. Venus lacks water, which makes crustal rock stronger and helps preserve surface features. The features observed provide evidence for the geological processes at work. Twenty feature types have been categorized thus far. These classes include local features, such as craters, coronae, and undae, as well as regional-scale features, such as planitiae, plana, and tesserae.
The upper plains unit is the remnants of a 50-100 meter thick mantling that has been discovered in the mid-latitudes of the planet Mars. It was first investigated in the Deuteronilus Mensae region, but it occurs in other places as well. The remnants consist of sets of dipping layers in impact craters, in depressions, and along mesas. Sets of dipping layers may be of various sizes and shapes—some look like Aztec pyramids from Central America.
EnVision is an orbital mission to Venus being developed by the European Space Agency (ESA) that is planned to perform high-resolution radar mapping and atmospheric studies. EnVision is designed to help scientists understand the relationships between its geological activity and the atmosphere, and it would investigate why Venus and Earth took such different evolutionary paths. The probe was selected as the fifth medium mission (M5) of ESA's Cosmic Vision programme in June 2021, with launch planned for 2031. The mission will be conducted in collaboration with NASA, with the potential sharing of responsibilities currently under assessment.
