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108-470: Gale is a crater , and probable dry lake , at 5°24′S 137°48′E  /  5.4°S 137.8°E  / -5.4; 137.8 in the northwestern part of the Aeolis quadrangle on Mars . It is 154 km (96 mi) in diameter and estimated to be about 3.5–3.8 billion years old. The crater was named after Walter Frederick Gale , an amateur astronomer from Sydney , Australia, who observed Mars in

216-486: A multispectral untargeted mode and a hyperspectral targeted mode. In the untargeted mode, CRISM reconnoiters Mars, recording approximately 50 of its 544 measurable wavelengths at a resolution of 100 to 200 meters per pixel. In this mode CRISM mapped half of Mars within a few months after aerobraking and most of the planet after one year. The objective of this mode is to identify new scientifically interesting locations that could be further investigated. In targeted mode,

324-433: A paraboloid (bowl-shaped) crater in which the centre has been pushed down, a significant volume of material has been ejected, and a topographically elevated crater rim has been pushed up. When this cavity has reached its maximum size, it is called the transient cavity. The depth of the transient cavity is typically a quarter to a third of its diameter. Ejecta thrown out of the crater do not include material excavated from

432-468: A certain altitude (retardation point), and start to accelerate again due to Earth's gravity until the body reaches its terminal velocity of 0.09 to 0.16 km/s. The larger the meteoroid (i.e. asteroids and comets) the more of its initial cosmic velocity it preserves. While an object of 9,000 kg maintains about 6% of its original velocity, one of 900,000 kg already preserves about 70%. Extremely large bodies (about 100,000 tonnes) are not slowed by

540-484: A cross-bedded or clinoform sandstone, though in places the base is a conglomerate. Thus, the formation is interpreted to have been deposited in a lacustrine environment adjacent to a fluvial-deltaic one. The Murray Formation is overlain by clay and sulfate-bearing strata. An unusual feature of Gale is an enormous mound of "sedimentary debris" around its central peak, officially named Aeolis Mons (popularly known as "Mount Sharp") rising 5.5 km (18,000 ft) above

648-519: A dense ancient Martian atmosphere did exist, it is probably not trapped in the crust. Understanding the composition of Mars' crust and how it changed with time tells us about many aspects of Mars' evolution as a planet, and was a major goal of CRISM. Remote and landed measurements prior to CRISM, and analysis of Martian meteorites, all suggest that the Martian crust is made mostly of basaltic igneous rock composed mostly of feldspar and pyroxene . Images from

756-404: A dryer, more saline and acidic environment in which sulfates formed. The MER Opportunity rover spent years exploring sedimentary rocks formed in the latter environment, full of sulfates, salts, and oxidized iron minerals. Soil forms from parent rocks through physical disintegration of rocks and by chemical alteration of the rock fragments. The types of soil minerals can reveal if the environment

864-547: A filtering step when the detector switches from a high luminosity area to shadows. Reportedly, 0.05% of the pixels were indicating perchlorate, now known to be a false high estimate by this instrument. However, both the Phoenix lander and the Curiosity rover measured 0.5% perchlorates in the soil, suggesting a global distribution of these salts. Perchlorate is of interest to astrobiologists , as it sequesters water molecules from

972-455: A hole in the surface without filling in nearby craters. This may explain the 'sponge-like' appearance of that moon. It is convenient to divide the impact process conceptually into three distinct stages: (1) initial contact and compression, (2) excavation, (3) modification and collapse. In practice, there is overlap between the three processes with, for example, the excavation of the crater continuing in some regions while modification and collapse

1080-405: A hole in the terrain, and the subsequent explosion ejected rocks and soil that landed around the crater. Layering in the central mound (Aeolis Mons) suggests it is the surviving remnant of an extensive sequence of deposits. Some scientists believe the crater filled in with sediments and, over time, the relentless Martian winds carved Aeolis Mons, which today rises about 5.5 km (3.4 mi) above

1188-627: A lake existed inside Gale shortly after the formation of the crater. The NASA Mars rover Curiosity , of the Mars Science Laboratory (MSL) mission, landed in "Yellowknife" Quad 51 of Aeolis Palus in Gale at 05:32 UTC August 6, 2012. NASA named the landing location Bradbury Landing on August 22, 2012. Curiosity is exploring Aeolis Mons and surrounding areas. Gale, named for Walter F. Gale (1865–1945), an amateur astronomer from Australia, spans 154 km (96 mi) in diameter and holds

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1296-452: A large impact. The subsequent excavation of the crater occurs more slowly, and during this stage the flow of material is largely subsonic. During excavation, the crater grows as the accelerated target material moves away from the point of impact. The target's motion is initially downwards and outwards, but it becomes outwards and upwards. The flow initially produces an approximately hemispherical cavity that continues to grow, eventually producing

1404-411: A leading model being carbon dioxide geysers . CRISM had watched the dark spots grow during southern spring, and found that bright streaks forming alongside the dark spots are made of fresh, new carbon dioxide frost, pointing like arrows back to their sources - the same sources as the dark spots. The bright streaks probably form by expansion, cooling, and freezing of the carbon dioxide gas, forming

1512-591: A lower layer that still retains its iron and magnesium. Some researchers have suggested that the Martian clay "layer cake" was created by soil-forming processes, including rainfall, at the time that valley networks formed. Lake and marine environments on Earth are favorable for fossil preservation, especially where the sediments they left behind are rich in carbonates or clays. Hundreds of highland craters on Mars have horizontally layered, sedimentary rocks that may have formed in lakes. CRISM has taken many targeted observations of these rocks to measure their mineralogy and how

1620-409: A mountain, Aeolis Mons (informally named "Mount Sharp" to pay tribute to geologist Robert P. Sharp ) rising 18,000 ft (5,500 m) from the crater floor, higher than Mount Rainier rises above Seattle. Gale is roughly the size of Connecticut and Rhode Island. The crater formed when an asteroid or comet hit Mars in its early history, about 3.5 to 3.8 billion years ago. The impactor punched

1728-530: A priority for CRISM, because hot springs would have had energy (geothermal heat) and water, two basic requirements for life. One of the signatures of hot springs on Earth is deposits of silica. The MER Spirit rover explored a silica-rich deposit called "Home Plate" that is thought to have formed in a hot spring. CRISM has discovered other silica-rich deposits in many locations. Some are associated with central peaks of impact craters, which are sites of heating driven by meteor impact. Silica has also been identified on

1836-558: A regular sequence with increasing size: small complex craters with a central topographic peak are called central peak craters, for example Tycho ; intermediate-sized craters, in which the central peak is replaced by a ring of peaks, are called peak-ring craters , for example Schrödinger ; and the largest craters contain multiple concentric topographic rings, and are called multi-ringed basins , for example Orientale . On icy (as opposed to rocky) bodies, other morphological forms appear that may have central pits rather than central peaks, and at

1944-409: A result, the impactor is compressed, its density rises, and the pressure within it increases dramatically. Peak pressures in large impacts exceed 1 T Pa to reach values more usually found deep in the interiors of planets, or generated artificially in nuclear explosions . In physical terms, a shock wave originates from the point of contact. As this shock wave expands, it decelerates and compresses

2052-644: A sample of articles of confirmed and well-documented impact sites. See the Earth Impact Database , a website concerned with 190 (as of July 2019 ) scientifically confirmed impact craters on Earth. There are approximately twelve more impact craters/basins larger than 300 km on the Moon, five on Mercury, and four on Mars. Large basins, some unnamed but mostly smaller than 300 km, can also be found on Saturn's moons Dione, Rhea and Iapetus. Compact Reconnaissance Imaging Spectrometer for Mars CRISM

2160-441: A significant crater volume may also be formed by the permanent compaction of the pore space . Such compaction craters may be important on many asteroids, comets and small moons. In large impacts, as well as material displaced and ejected to form the crater, significant volumes of target material may be melted and vaporized together with the original impactor. Some of this impact melt rock may be ejected, but most of it remains within

2268-406: A small angle, and high-temperature highly shocked material is expelled from the convergence zone with velocities that may be several times larger than the impact velocity. In most circumstances, the transient cavity is not stable and collapses under gravity. In small craters, less than about 4 km diameter on Earth, there is some limited collapse of the crater rim coupled with debris sliding down

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2376-413: Is about 4,400 m (14,400 ft) below Martian "sea level" (defined as the average elevation around the equator). The expected near-surface atmospheric temperatures at the landing site during Curiosity ' s primary mission (1 Martian year or 687 Earth days) are from −90 to 0 °C (−130 to 32 °F). Scientists chose Gale as the landing site for Curiosity because it has many signs that water

2484-402: Is already underway in others. In the absence of atmosphere , the impact process begins when the impactor first touches the target surface. This contact accelerates the target and decelerates the impactor. Because the impactor is moving so rapidly, the rear of the object moves a significant distance during the short-but-finite time taken for the deceleration to propagate across the impactor. As

2592-512: Is ejected from close to the center of impact, and the slowest material is ejected close to the rim at low velocities to form an overturned coherent flap of ejecta immediately outside the rim. As ejecta escapes from the growing crater, it forms an expanding curtain in the shape of an inverted cone. The trajectory of individual particles within the curtain is thought to be largely ballistic. Small volumes of un-melted and relatively un-shocked material may be spalled at very high relative velocities from

2700-459: Is estimated that the value of materials mined from impact structures is five billion dollars/year just for North America. The eventual usefulness of impact craters depends on several factors, especially the nature of the materials that were impacted and when the materials were affected. In some cases, the deposits were already in place and the impact brought them to the surface. These are called "progenetic economic deposits." Others were created during

2808-448: Is furthest from the Sun (at aphelion), there is an equatorial water-ice cloud belt and very little dust in the atmosphere. Atmospheric water vapor varies in abundance seasonally, with the greatest abundances in each hemisphere's summer after the seasonal polar caps have sublimated into the atmosphere. During winter, both water and carbon dioxide frost and ices form on Mars' surface. These ices form

2916-613: Is not the case–water stayed for some time. Also, with water coming and going on a regular pace, there is a better chance of more complex organic compounds being produced. As water evaporates chemicals are concentrated and have a better chance of combining. For example when amino acids are concentrated they are more likely to link up to form proteins. Curiosity found features that computer simulations show could be caused by past streams. They have been called benches and noses. The "noses" stick out like noses. Computer simulations show that these shapes can be produced by rivers. In July 2024

3024-404: Is sufficient to melt the impactor, and in larger impacts to vaporize most of it and to melt large volumes of the target. As well as being heated, the target near the impact is accelerated by the shock wave, and it continues moving away from the impact behind the decaying shock wave. Contact, compression, decompression, and the passage of the shock wave all occur within a few tenths of a second for

3132-437: Is the largest goldfield in the world, which has supplied about 40% of all the gold ever mined in an impact structure (though the gold did not come from the bolide). The asteroid that struck the region was 9.7 km (6 mi) wide. The Sudbury Basin was caused by an impacting body over 9.7 km (6 mi) in diameter. This basin is famous for its deposits of nickel , copper , and platinum group elements . An impact

3240-771: The Curiosity rover will continue to explore higher and younger layers of Mount Sharp in order to determine how the lake environment in ancient times on Mars became the drier environment in more modern times. On August 5, 2017, NASA celebrated the fifth anniversary of the Curiosity rover mission landing, and related exploratory accomplishments, on the planet Mars . (Videos: Curiosity 's First Five Years (02:07) ; Curiosity 's POV: Five Years Driving (05:49) ; Curiosity 's Discoveries About Gale Crater (02:54) ) On June 7, 2018, NASA 's Curiosity made two significant discoveries in Gale. Organic molecules preserved in 3.5 billion-year-old bedrock and seasonal variations in

3348-547: The Curiosity rover, that there was plenty of water on early Mars . In January 2020, researchers have found certain minerals, made of carbon and oxygen, in rocks at Gale, which may have formed in an ice-covered lake during a cold stage between warmer periods, or after Mars lost most of its atmosphere and became permanently cold. On November 5, 2020, researchers concluded based on data observed by Curiosity rover that Gale experienced megafloods which occurred around 4 billion years ago, taking into consideration antidunes reaching

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3456-652: The Isidis basin , in the Noachian plains surrounding Valles Marineris , and in Noachian plains surrounding the Tharsis plateau. The global distribution of layered clays suggests a global process. Layered clays are late Noachian in age, dating from the same time as water-carved valley networks. The layered clay composition is similar to what is expected for soil formation on Earth - a weathered upper layer leached of soluble iron and magnesium, leaving an insoluble aluminum-rich residue, with

3564-583: The MER Spirit rover identified outcrops rich in magnesium-iron carbonate (16–34 wt%) in the Columbia Hills of Gusev crater . Later CRISM analyses identified carbonates in the rim of Huygens crater which suggested that there could be extensive deposits of buried carbonates on Mars. However, a study by CRISM scientists estimated that all of the carbonate rock on Mars holds less than the present Martian atmosphere worth of carbon dioxide. They determined that if

3672-645: The Mars Exploration Rovers (MER; 2003–2019), the TES thermal emission spectrometer on Mars Global Surveyor (MGS; 1997-2006), and the THEMIS thermal imaging system on Mars Odyssey (2004–present) helped to frame the themes for CRISM's exploration: In November 2018, it was announced that CRISM had fabricated some additional pixels representing the minerals alunite, kieserite, serpentine and perchlorate. The instrument team found that some false positives were caused by

3780-1380: The Mars Orbiter Camera on MGS showed that in some places the upper few kilometers of the crust is composed of hundreds of thin volcanic lava flows. TES and THEMIS both found mostly basaltic igneous rock, with scattered olivine-rich and even some quartz-rich rocks. The first recognition of widespread sedimentary rock on Mars came from the Mars Orbiter Camera which found that several areas of the planet - including Valles Marineris and Terra Arabia - have horizontally layered, light-toned rocks. Follow-up observations of those rocks' mineralogy by OMEGA found that some are rich in sulfate minerals, and that other layered rocks around Mawrth Vallis are rich in phyllosilicates. Both class of minerals are signatures of sedimentary rocks. CRISM had used its improved spatial resolution to look for other deposits of sedimentary rock on Mars' surface, and for layers of sedimentary rock buried between layers of volcanic rock in Mars' crust. To understand Mars' ancient climate, and whether it might have created environments habitable for life, first we need to understand Mars' climate today. Each mission to Mars has made new advances in understanding its climate. Mars has seasonal variations in

3888-716: The Mars Science Laboratory spacecraft, which was launched November 26, 2011 and landed on Mars inside the crater Gale on the plains of Aeolis Palus on August 6, 2012. Gale was previously a candidate landing site for the 2003 Mars Exploration Rover mission, and has been one of four prospective sites for ESA 's ExoMars . In December 2012, scientists working on the Mars Science Laboratory mission announced that an extensive soil analysis of Martian soil performed by Curiosity showed evidence of water molecules , sulphur and chlorine , as well as hints of organic compounds . However, terrestrial contamination, as

3996-489: The Nevada Test Site , notably Jangle U in 1951 and Teapot Ess in 1955. In 1960, Edward C. T. Chao and Shoemaker identified coesite (a form of silicon dioxide ) at Meteor Crater, proving the crater was formed from an impact generating extremely high temperatures and pressures. They followed this discovery with the identification of coesite within suevite at Nördlinger Ries , proving its impact origin. Armed with

4104-426: The density of Mount Sharp in Gale, thereby establishing a clearer understanding of how the mountain was formed. Gale is located at about 5°24′S 137°48′E  /  5.4°S 137.8°E  / -5.4; 137.8 on Mars. Numerous channels eroded into the flanks of the crater's central mound could give access to the layers for study. Gale is the landing site of the Curiosity rover, delivered by

4212-429: The speed of sound in those objects. Such hyper-velocity impacts produce physical effects such as melting and vaporization that do not occur in familiar sub-sonic collisions. On Earth, ignoring the slowing effects of travel through the atmosphere, the lowest impact velocity with an object from space is equal to the gravitational escape velocity of about 11 km/s. The fastest impacts occur at about 72 km/s in

4320-399: The stable interior regions of continents . Few undersea craters have been discovered because of the difficulty of surveying the sea floor, the rapid rate of change of the ocean bottom, and the subduction of the ocean floor into Earth's interior by processes of plate tectonics . Daniel M. Barringer, a mining engineer, was convinced already in 1903 that the crater he owned, Meteor Crater ,

4428-486: The "worst case" scenario in which an object in a retrograde near-parabolic orbit hits Earth. The median impact velocity on Earth is about 20 km/s. However, the slowing effects of travel through the atmosphere rapidly decelerate any potential impactor, especially in the lowest 12 kilometres where 90% of the Earth's atmospheric mass lies. Meteors of up to 7,000 kg lose all their cosmic velocity due to atmospheric drag at

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4536-631: The Rover cracked open a rock with its wheel and found crystals of sulfur . Minerals containing sulfur were discovered, but never the pure element. It was found in Gediz Vallis. Impact crater An impact crater is a depression in the surface of a solid astronomical body formed by the hypervelocity impact of a smaller object. In contrast to volcanic craters , which result from explosion or internal collapse, impact craters typically have raised rims and floors that are lower in elevation than

4644-688: The Stimson formation is the only stratigraphic unit within the Siccar Point group which has been investigated in-detail by Curiosity . The Stimson formation represents the preserved expression of a dry aeolian dune field , where sediment was transported towards the north, or northeast by palaeowinds within the crater. In the Emerson plateau area (from Marias Pass, to East Glacier), the outcrops are characterised predominantly by simple cross-sets, deposited by simple sinuous-crested dunes, with heights up to ~10 m. To

4752-419: The abundances of water vapor, water ice clouds and hazes, and atmospheric dust. During southern summer, when Mars is closest to the Sun (at perihelion), solar heating can raise massive dust storms. Regional dust storms - ones having a 1000-kilometer scale - show surprising repeatability Mars-year to Mars-year. Once every decade or so, they grow into global-scale events. In contrast, during northern summer when Mars

4860-469: The actual impact. The great energy involved caused melting. Useful minerals formed as a result of this energy are classified as "syngenetic deposits." The third type, called "epigenetic deposits," is caused by the creation of a basin from the impact. Many of the minerals that our modern lives depend on are associated with impacts in the past. The Vredeford Dome in the center of the Witwatersrand Basin

4968-528: The amounts of methane in the atmosphere of the planet Mars ; in addition, organic chemicals were detected in powder drilled from a rock . Also, based on deuterium to hydrogen ratio studies, much of the water at Gale on Mars was found to have been lost during ancient times, before the lakebed in the crater was formed; afterwards, large amounts of water continued to be lost. On October 8, 2015, NASA confirmed that lakes and streams existed in Gale 3.3 to 3.8 billion years ago delivering sediments to build up

5076-469: The association of volcanic flows and other volcanic materials. Impact craters produce melted rocks as well, but usually in smaller volumes with different characteristics. The distinctive mark of an impact crater is the presence of rock that has undergone shock-metamorphic effects, such as shatter cones , melted rocks, and crystal deformations. The problem is that these materials tend to be deeply buried, at least for simple craters. They tend to be revealed in

5184-446: The atmosphere - not heating of the atmospheric gases - is more important in driving weather. Small, suspended particles of dust and water ice - aerosols - intercept 20–30% of incoming sunlight, even under relatively clear conditions. So variations in the amounts of these aerosols have a huge influence on climate. CRISM had taken three major kinds of measurements of dust and ice in the atmosphere: targeted observations whose repeated views of

5292-576: The atmosphere and reduces its freezing point, potentially creating thin films of watery brine that —although toxic to most Earth life— it could potentially offer habitats for native Martian microbes in the shallow subsurface. (See: Life on Mars#Perchlorates ) Aqueous minerals are minerals that form in water, either by chemical alteration of pre-existing rock or by precipitation out of solution. The minerals indicate where liquid water existed long enough to react chemically with rock. Which minerals form depends on temperature, salinity, pH , and composition of

5400-432: The atmosphere at all, and impact with their initial cosmic velocity if no prior disintegration occurs. Impacts at these high speeds produce shock waves in solid materials, and both impactor and the material impacted are rapidly compressed to high density. Following initial compression, the high-density, over-compressed region rapidly depressurizes, exploding violently, to set in train the sequence of events that produces

5508-451: The collapse and modification of the transient cavity is much more extensive, and the resulting structure is called a complex crater . The collapse of the transient cavity is driven by gravity, and involves both the uplift of the central region and the inward collapse of the rim. The central uplift is not the result of elastic rebound, which is a process in which a material with elastic strength attempts to return to its original geometry; rather

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5616-468: The collapse is a process in which a material with little or no strength attempts to return to a state of gravitational equilibrium . Complex craters have uplifted centers, and they have typically broad flat shallow crater floors, and terraced walls . At the largest sizes, one or more exterior or interior rings may appear, and the structure may be labeled an impact basin rather than an impact crater. Complex-crater morphology on rocky planets appears to follow

5724-617: The crater completely, possibly originally deposited on a lakebed. Evidence of fluvial activity was observed early on in the mission at the Shaler outcrop (first observed on Sol 120, investigated extensively between Sols 309-324). Observations made by the rover Curiosity at the Pahrump Hills strongly support the lake hypothesis: sedimentary facies including sub mm-scale horizontally-laminated mudstones, with interbedded fluvial crossbeds are representative of sediments which accumulate in lakes, or on

5832-451: The crater walls and drainage of impact melts into the deeper cavity. The resultant structure is called a simple crater, and it remains bowl-shaped and superficially similar to the transient crater. In simple craters, the original excavation cavity is overlain by a lens of collapse breccia , ejecta and melt rock, and a portion of the central crater floor may sometimes be flat. Above a certain threshold size, which varies with planetary gravity,

5940-405: The craters on the Moon as logical impact sites that were formed not gradually, in eons , but explosively, in seconds." For his PhD degree at Princeton University (1960), under the guidance of Harry Hammond Hess , Shoemaker studied the impact dynamics of Meteor Crater. Shoemaker noted that Meteor Crater had the same form and structure as two explosion craters created from atomic bomb tests at

6048-544: The dominant geographic features on many solid Solar System objects including the Moon , Mercury , Callisto , Ganymede , and most small moons and asteroids . On other planets and moons that experience more active surface geological processes, such as Earth , Venus , Europa , Io , Titan , and Triton , visible impact craters are less common because they become eroded , buried, or transformed by tectonic and volcanic processes over time. Where such processes have destroyed most of

6156-407: The expanding vapor cloud may rise to many times the scale height of the atmosphere, effectively expanding into free space. Most material ejected from the crater is deposited within a few crater radii, but a small fraction may travel large distances at high velocity, and in large impacts it may exceed escape velocity and leave the impacted planet or moon entirely. The majority of the fastest material

6264-601: The fans' lowermost layers, there are concentrated deposits of clay. More clay occurs beyond the end of the fans on the crater floors, and in some cases there is also opal. On Earth, the lowermost layers of deltas are called bottom set beds, and they are made of clays that settled out of inflowing river water in quiet, deep parts of the lakes. This discovery supports the idea that many fans formed in crater lakes where, potentially, evidence for habitable environments could be preserved. Not all ancient Martian lakes were fed by inflowing valley networks. CRISM discovered several craters on

6372-544: The flanks of volcanic inside the caldera of the Syrtis Major shield volcano, forming light-colored mounds that look like scaled-up versions of Home Plate . Elsewhere, in the westernmost parts of Valles Marineris, near the core of the Tharsis volcanic province, there are sulfate and clay deposits suggestive of "warm" springs. Hot spring deposits are one of the most promising areas on Mars to search for evidence for past life. One of

6480-541: The floor of Gale—three times higher than the Grand Canyon is deep. At 10:32 p.m. PDT on August 5, 2012 (1:32 a.m. EDT on August 6, 2012), the Mars Science Laboratory rover Curiosity landed on Mars at 4°30′S 137°24′E  /  4.5°S 137.4°E  / -4.5; 137.4 , at the foot of the layered mountain inside Gale. Curiosity landed within a landing ellipse approximately 7 km (4.3 mi) by 20 km (12 mi). The landing ellipse

6588-401: The full depth of the transient cavity; typically the depth of maximum excavation is only about a third of the total depth. As a result, about one third of the volume of the transient crater is formed by the ejection of material, and the remaining two thirds is formed by the displacement of material downwards, outwards and upwards, to form the elevated rim. For impacts into highly porous materials,

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6696-448: The geologists John D. Boon and Claude C. Albritton Jr. revisited Bucher's studies and concluded that the craters that he studied were probably formed by impacts. Grove Karl Gilbert suggested in 1893 that the Moon's craters were formed by large asteroid impacts. Ralph Baldwin in 1949 wrote that the Moon's craters were mostly of impact origin. Around 1960, Gene Shoemaker revived the idea. According to David H. Levy , Shoemaker "saw

6804-555: The goals that drove CRISM's design was to find carbonates, to try to solve this question about what happened to Mars' atmosphere. And one of CRISM's most important discoveries was the identification of carbonate bedrock in Nili Fossae in 2008. Soon thereafter, landed missions to Mars started identifying carbonates on the surface; the Phoenix Mars lander found between 3–5 wt% calcite (CaCO 3 ) at its northern lowland landing site, while

6912-610: The height of 10 meters (33 ft), which were formed by flood waters at least 24 meters (79 ft) deep with a velocity of 10 meters per second (22 mph). Research published in August, 2023 found evidence that liquid water may have existed for a long time and not just when an impact or volcano erupted. Shapes in a field of hexagonal ridges revealed that water appeared and then went away many times. The water did not just result from ground ice melting from something like an asteroid impact. To make these ridges many cycles of water saturating

7020-599: The impact crater. Impact-crater formation is therefore more closely analogous to cratering by high explosives than by mechanical displacement. Indeed, the energy density of some material involved in the formation of impact craters is many times higher than that generated by high explosives. Since craters are caused by explosions , they are nearly always circular – only very low-angle impacts cause significantly elliptical craters. This describes impacts on solid surfaces. Impacts on porous surfaces, such as that of Hyperion , may produce internal compression without ejecta, punching

7128-521: The impactor, and it accelerates and compresses the target. Stress levels within the shock wave far exceed the strength of solid materials; consequently, both the impactor and the target close to the impact site are irreversibly damaged. Many crystalline minerals can be transformed into higher-density phases by shock waves; for example, the common mineral quartz can be transformed into the higher-pressure forms coesite and stishovite . Many other shock-related changes take place within both impactor and target as

7236-493: The instrument to perform emission phase functions, viewing the same surface through variable amounts of atmosphere, which would be used to determine atmospheric properties. The Data Processing Unit (DPU) of CRISM performs in-flight data processing including compressing the data before transmission. CRISM began its exploration of Mars in late 2006. Results from the OMEGA visible/near-infrared spectrometer on Mars Express (2003–present),

7344-725: The knowledge of shock-metamorphic features, Carlyle S. Beals and colleagues at the Dominion Astrophysical Observatory in Victoria, British Columbia , Canada and Wolf von Engelhardt of the University of Tübingen in Germany began a methodical search for impact craters. By 1970, they had tentatively identified more than 50. Although their work was controversial, the American Apollo Moon landings, which were in progress at

7452-649: The largest sizes may contain many concentric rings. Valhalla on Callisto is an example of this type. Long after an impact event, a crater may be further modified by erosion, mass wasting processes, viscous relaxation, or erased entirely. These effects are most prominent on geologically and meteorologically active bodies such as Earth, Titan, Triton, and Io. However, heavily modified craters may be found on more primordial bodies such as Callisto, where many ancient craters flatten into bright ghost craters, or palimpsests . Non-explosive volcanic craters can usually be distinguished from impact craters by their irregular shape and

7560-464: The late 19th century. Mount Sharp is a mountain in the center of Gale and rises 5.5 km (18,000 ft) high. Aeolis Palus is the plain between the northern wall of Gale and the northern foothills of Aeolis Mons. Peace Vallis , a nearby outflow channel , 'flows' down from the hills to the Aeolis Palus below and seems to have been carved by flowing water . Several lines of evidence suggest that

7668-495: The leading hypotheses for why ancient Mars was wetter than today is that a thick, carbon dioxide-rich atmosphere created a global greenhouse, that warmed the surface enough for liquid water to occur in large amounts. Carbon dioxide ice in today's polar caps is too limited in volume to hold that ancient atmosphere. If a thick atmosphere ever existed, it was either blown into space by solar wind or impacts, or reacted with silicate rocks to become trapped as carbonates in Mars' crust. One of

7776-477: The level of methane in the atmosphere further support the theory that past conditions may have been conducive to life. It is possible that a form of water-rock chemistry might have generated the methane, but scientists cannot rule out the possibility of biological origins. Methane previously had been detected in Mars' atmosphere in large, unpredictable plumes. This new result shows that low levels of methane within Gale repeatedly peak in warm, summer months and drop in

7884-429: The lower layers of Mount Sharp . On June 1, 2017, NASA reported that the Curiosity rover provided evidence of an ancient lake in Gale on Mars that could have been favorable for microbial life ; the ancient lake was stratified , with shallows rich in oxidants and depths poor in oxidants; and, the ancient lake provided many different types of microbe-friendly environments at the same time. NASA further reported that

7992-565: The margins of lakes which grow and contract in response to lake-level. These lake-bed mudstones are referred to as the Murray Formation , and form a significant amount of the Mount Sharp group. The Siccar Point group (named after the famous unconformity at Siccar Point ) overlies the Mount Sharp group, and the two units are separated by a major unconformity which dips toward the North. At present,

8100-441: The minerals vary between layers. Variation between layers helps us to understand the sequence of events that formed the sedimentary rocks. The Mars Orbiter Camera found that where valley networks empty into craters, commonly the craters contain fan-shaped deposits. However it was not completely clear if the fans formed by sediment deposition on dry crater floors ( alluvial fans ) or in crater lakes ( deltas ). CRISM discovered that in

8208-401: The northern crater floor and 4.5 km (15,000 ft) above the southern crater floor—slightly taller than the southern rim of the crater itself. The mound is composed of layered material and may have been laid down over a period of around 2 billion years. The origin of this mound is not known with certainty, but research suggests it is the eroded remnant of sedimentary layers that once filled

8316-411: The original crater topography , the terms impact structure or astrobleme are more commonly used. In early literature, before the significance of impact cratering was widely recognised, the terms cryptoexplosion or cryptovolcanic structure were often used to describe what are now recognised as impact-related features on Earth. The cratering records of very old surfaces, such as Mercury, the Moon, and

8424-701: The outer Solar System could be different from the inner Solar System. Although Earth's active surface processes quickly destroy the impact record, about 190 terrestrial impact craters have been identified. These range in diameter from a few tens of meters up to about 300 km (190 mi), and they range in age from recent times (e.g. the Sikhote-Alin craters in Russia whose creation was witnessed in 1947) to more than two billion years, though most are less than 500 million years old because geological processes tend to obliterate older craters. They are also selectively found in

8532-660: The overlying Mount Sharp Group. Formations within the Bradbury Group include the Yellowknife and Kimberley, while the Murray Formation is at the base of the Mount Sharp Group. The Bradbury Group consists of fluvial conglomerates , cross-bedded sandstones , and mudstones reflecting a basaltic provenance . Sandstone clinoforms indicate deltaic deposits . The Murray Formation is a laminated mudstone overlain by

8640-852: The parent rock. Which aqueous minerals are present on Mars therefore provides important clues to understanding past environments. The OMEGA spectrometer on the Mars Express orbiter and the MER rovers both uncovered evidence for aqueous minerals. OMEGA revealed two distinct kinds of past aqueous deposits. The first, containing sulfates such as gypsum and kieserite, is found in layered deposits of Hesperian age (Martian middle age, roughly from 3.7 to 3 billion years ago). The second, rich in several different kinds of phyllosilicates, instead occurs rocks of Noachian age (older than about 3.7 billion years). The different ages and mineral chemistries suggest an early water-rich environment in which phyllosilicates formed, followed by

8748-534: The past, including: Pancake Delta, Western Delta, Farah Vallis delta and the Peace Vallis Fan. Orbital THEMIS and topography data, plus visible and near-infrared images, were used to make a geologic map of the crater. CRISM data indicated the lower bench unit was composed of interstratified clay and sulfates . Curiosity explored the stratigraphy of the crater consisting of the Bradbury Group and

8856-595: The pediment capping unit. Observations made during the ascent of the Greenheugh pediment between Sols 2665-2734 demonstrated that the pediment capping unit has sedimentary textures, facies and architecture that are consistent with the rest of the Stimson formation. Furthermore, analysis of sedimentary facies and architecture provided evidence which indicates fluctuating wind directions, from a seasonal temporal scale - recorded by interstratified windripple and avalanche strata, through to millennial time scales recorded by reversal of

8964-473: The planet than have been discovered so far. The cratering rate in the inner solar system fluctuates as a consequence of collisions in the asteroid belt that create a family of fragments that are often sent cascading into the inner solar system. Formed in a collision 80 million years ago, the Baptistina family of asteroids is thought to have caused a large spike in the impact rate. The rate of impact cratering in

9072-489: The presence of water. All of these materials have characteristic patterns in their visible-infrared reflections and were readily seen by CRISM. In addition, CRISM was monitoring ice and dust particulates in the Martian atmosphere to learn more about its climate and seasons. CRISM measured visible and infrared electromagnetic radiation from 362 to 3920 nanometers in 6.55 nanometer increments. The instrument had two modes,

9180-424: The seasonal and residual polar caps. The seasonal caps - which form each autumn and sublimate each spring - are dominated by carbon dioxide ice. The residual caps - which persist year after year - consist mostly of water ice at the north pole and water ice with a thin veneer (a few 10's of meters thick) of carbon dioxide ice at the south pole. Mars' atmosphere is so thin and wispy that solar heating of dust and ice in

9288-456: The sediment transport direction. These wind reversals suggest variable and changeable atmospheric circulation during this time. Observations of possible cross-bedded strata on the upper mound suggest aeolian processes , but the origin of the lower mound layers remains ambiguous. In February 2019, NASA scientists reported that the Mars Curiosity rover had determined, for the first time,

9396-419: The shock wave passes through, and some of these changes can be used as diagnostic tools to determine whether particular geological features were produced by impact cratering. As the shock wave decays, the shocked region decompresses towards more usual pressures and densities. The damage produced by the shock wave raises the temperature of the material. In all but the smallest impacts this increase in temperature

9504-525: The source of the organic compounds, could not be ruled out. On September 26, 2013, NASA scientists reported that Curiosity detected "abundant, easily accessible" water (1.5 to 3 weight percent) in soil samples at the Rocknest region of Aeolis Palus in Gale. In addition, the rover found two principal soil types: a fine-grained mafic type and a locally derived, coarse-grained felsic type . The mafic type, similar to other martian soils and martian dust ,

9612-559: The south, at the Murray buttes, the outcrop are characterised by compound cross-sets, with a hierarchy of bounding surfaces migration of small dunes superimposed on the lee-slope of a large dune known as a " draa ". These draas have estimates heights of ~40 m, and migrated toward the north, while superimposed dunes migrated toward the east-northeast. Further to the south, at the Greenheugh pediment, compound and simple cross-sets consistent with aeolian depositional processes have been observed in

9720-464: The southern highlands of Mars, record a period of intense early bombardment in the inner Solar System around 3.9 billion years ago. The rate of crater production on Earth has since been considerably lower, but it is appreciable nonetheless. Earth experiences, on average, from one to three impacts large enough to produce a 20-kilometre-diameter (12 mi) crater every million years. This indicates that there should be far more relatively young craters on

9828-688: The spectrometer measured energy in all 544 wavelengths. When the MRO spacecraft is at an altitude of 300 km, CRISM detects a narrow but long strip on the Martian surface about 18 kilometers across and 10,800 kilometers long. The instrument swept this strip across the surface as MRO orbits Mars to image the surface. The data collecting part of CRISM was called the Optical Sensor Unit (OSU) and consisted of two spectrographs, one that detected visible light from 400 to 830 nm and one that detected infrared light from 830 to 4050 nm. The infrared detector

9936-473: The surface and then drying were required. Chemicals were deposited by mineral-rich fluids in cracks. The minerals hardened such that they were harder than the rock around them. Later, when erosion took place, ridges were exposed. This discovery is significant. Much evidence exists to show that impacts and volcanic activity could melt ground ice to make liquid water. However, that water may not last long enough for life to develop. This new finding shows here it

10044-425: The surface of the target and from the rear of the impactor. Spalling provides a potential mechanism whereby material may be ejected into inter-planetary space largely undamaged, and whereby small volumes of the impactor may be preserved undamaged even in large impacts. Small volumes of high-speed material may also be generated early in the impact by jetting. This occurs when two surfaces converge rapidly and obliquely at

10152-532: The surface provide a sensitive estimate of aerosol abundance; special global grids of targeted observations every couple of months designed especially to track spatial and seasonal variations; and scans across the planet's limb to show how dust and ice vary with height above the surface. The south polar seasonal cap has a bizarre variety of bright and dark streaks and spots that appear during spring, as carbon dioxide ice sublimates. Prior to MRO there were various ideas for processes that could form these strange features,

10260-500: The surrounding terrain. Impact craters are typically circular, though they can be elliptical in shape or even irregular due to events such as landslides. Impact craters range in size from microscopic craters seen on lunar rocks returned by the Apollo Program to simple bowl-shaped depressions and vast, complex, multi-ringed impact basins . Meteor Crater is a well-known example of a small impact crater on Earth. Impact craters are

10368-473: The time, provided supportive evidence by recognizing the rate of impact cratering on the Moon . Because the processes of erosion on the Moon are minimal, craters persist. Since the Earth could be expected to have roughly the same cratering rate as the Moon, it became clear that the Earth had suffered far more impacts than could be seen by counting evident craters. Impact cratering involves high velocity collisions between solid objects, typically much greater than

10476-411: The transient crater, initially forming a layer of impact melt coating the interior of the transient cavity. In contrast, the hot dense vaporized material expands rapidly out of the growing cavity, carrying some solid and molten material within it as it does so. As this hot vapor cloud expands, it rises and cools much like the archetypal mushroom cloud generated by large nuclear explosions. In large impacts,

10584-403: The uplifted center of a complex crater, however. Impacts produce distinctive shock-metamorphic effects that allow impact sites to be distinctively identified. Such shock-metamorphic effects can include: On Earth, impact craters have resulted in useful minerals. Some of the ores produced from impact related effects on Earth include ores of iron , uranium , gold , copper , and nickel . It

10692-424: The way to Glenelg , was a mugearite and very similar to terrestrial mugearite rocks. On December 9, 2013, NASA reported that, based on evidence from Curiosity studying Aeolis Palus, Gale contained an ancient freshwater lake which could have been a hospitable environment for microbial life . On December 16, 2014, NASA reported detecting, by the Curiosity rover at Gale, an unusual increase, then decrease, in

10800-402: The western slope of Tharsis that contain "bathtub rings" of sulfate minerals and a kind of phyllosilicate called kaolinite. Both minerals can form together by precipitating out of acidic, saline water. These craters lack inflowing valley networks, showing that they were not fed by rivers - instead, they must have been fed by inflowing groundwater. The identification of hot spring deposits was

10908-462: The winter every year. Organic carbon concentrations were discovered on the order of 10 parts per million or more. This is close to the amount observed in Martian meteorites and about 100 times greater than prior analysis of organic carbon on Mars' surface. Some of the molecules identified include thiophenes, benzene, toluene, and small carbon chains, such as propane or butene. On November 4, 2018, geologists presented evidence, based on studies in Gale by

11016-456: Was associated with hydration of the amorphous phases of the soil. Also, perchlorates , the presence of which may make detection of life-related organic molecules difficult, were found at the Curiosity landing site (and earlier at the more polar site of the Phoenix lander ) suggesting a "global distribution of these salts". NASA also reported that Jake M rock , a rock encountered by Curiosity on

11124-461: Was being used to identify locations on Mars that may have hosted water , a solvent considered important in the search for past or present life on Mars . In order to do this, CRISM was mapping the presence of minerals and chemicals that may indicate past interaction with water - low-temperature or hydrothermal . These materials include iron and oxides , which can be chemically altered by water, and phyllosilicates and carbonates , which form in

11232-522: Was cool or warm, wet or dry, or whether the water was fresh or salty. Because CRISM is able to detect many minerals in the soil or regolith, the instrument is being used to help decipher ancient Martian environments. CRISM has found a characteristic layering pattern of aluminum-rich clays overlying iron- and magnesium-rich clays in many areas scattered through Mars' highlands. Surrounding Mawrth Vallis , these "layered clays" cover hundreds of thousands of square kilometers. Similar layering occurs near

11340-422: Was cooled to –173° Celsius (–280° Fahrenheit ) by a radiator plate and three cryogenic coolers. While in targeted mode, the instrument gimbals in order to continue pointing at one area even though the MRO spacecraft is moving. The extra time collecting data over a targeted area increases the signal-to-noise ratio as well as the spatial and spectral resolution of the image. This scanning ability also allowed

11448-666: Was involved in making the Carswell structure in Saskatchewan , Canada; it contains uranium deposits. Hydrocarbons are common around impact structures. Fifty percent of impact structures in North America in hydrocarbon-bearing sedimentary basins contain oil/gas fields. On Earth, the recognition of impact craters is a branch of geology, and is related to planetary geology in the study of other worlds. Out of many proposed craters, relatively few are confirmed. The following twenty are

11556-507: Was of cosmic origin. Most geologists at the time assumed it formed as the result of a volcanic steam eruption. In the 1920s, the American geologist Walter H. Bucher studied a number of sites now recognized as impact craters in the United States. He concluded they had been created by some great explosive event, but believed that this force was probably volcanic in origin. However, in 1936,

11664-464: Was present over its history. The crater's geology is notable for containing both clays and sulfate minerals, which form in water under different conditions and may also preserve signs of past life. The history of water at Gale, as recorded in its rocks, is giving Curiosity many clues to study as it pieces together whether Mars ever could have been a habitat for microbes. Gale contains a number of fans and deltas that provide information about lake levels in

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