Misplaced Pages

#240759

85-463: Attica may be divided into five natural parts: North-east of the Athenian plain, between Parnes, Pentelicus, and the sea, is a mountain district, known by the name of Diacria (Διακρία) in antiquity. Its inhabitants, usually called Diacreis or Diacrii (Διακρεῖς, Diakreis or Διακρίοι, Diakrioi ), were sometimes also termed Hyperacrii (Ὑπερακρίοι. Hyperakrioi ), apparently from their dwelling on

170-479: 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 (Mars Chart-2). The Diacria quadrangle covers parts of Arcadia Planitia and Amazonis Planitia . The southern and northern borders of the Diacria quadrangle are approximately 3,065 km (1,905 mi) and 1,500 km (930 mi) wide, respectively. The north to south distance

255-416: A change in velocity of 180 m/s (590 ft/s). These nozzles also acted as the control thrusters for translation and rotation of the lander. Terminal descent (after use of a parachute ) and landing used three (one affixed on each long side of the base, separated by 120 degrees) monopropellant hydrazine engines. The engines had 18 nozzles to disperse the exhaust and minimize effects on

340-481: A deorbit burn . The lander then experienced atmospheric entry with peak heating occurring a few seconds after the start of frictional heating with the Martian atmosphere. At an altitude of about 6 kilometers (3.7 miles) and traveling at a velocity of 900 kilometers per hour (600 mph), the parachute deployed, the aeroshell released and the lander's legs unfolded. At an altitude of about 1.5 kilometers (5,000 feet),

425-476: A 40-Mbit tape recorder, and the lander computer had a 6000- word memory for command instructions. The lander carried instruments to achieve the primary scientific objectives of the lander mission: to study the biology , chemical composition ( organic and inorganic ), meteorology , seismology , magnetic properties, appearance, and physical properties of the Martian surface and atmosphere. Two 360-degree cylindrical scan cameras were mounted near one long side of

510-434: A cruise Sun sensor, a Canopus star tracker and an inertial reference unit consisting of six gyroscopes allowed three-axis stabilization. Two accelerometers were also on board. Communications were accomplished through a 20 W S-band (2.3 GHz ) transmitter and two 20 W TWTAs . An X band (8.4 GHz) downlink was also added specifically for radio science and to conduct communications experiments. Uplink

595-574: A gas. This is similar to what happens to dry ice on the Earth. Places on Mars that display polygonal ground may indicate where future colonists can find water ice. Patterned ground forms in a mantle layer, called latitude dependent mantle , that fell from the sky when the climate was different. The western flank of the Alba Mons volcano makes up the eastern and southeastern edge of the quadrangle. In terms of area, Alba Mons (formerly, Alba Patera)

680-476: 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. Inverted relief has been observed on

765-561: A layer of younger material. At the resolution of the Mars Orbital Camera (MOC) on the Mars Global Surveyor spacecraft (around several m per pixel), much of the northern plains has a distinctly stippled, pitted texture that causes the ground to resemble the surface of a basketball or orange rind. This texture is likely caused by a mantle of ice and dust covering the landscape. The small hollows and pits formed as

850-412: A mass of 13.6 kg (30 lb) and provided 30 watts of continuous power at 4.4 volts. Four wet cell sealed nickel-cadmium 8 Ah (28,800  coulombs ), 28 volt rechargeable batteries were also on board to handle peak power loads. Communications were accomplished through a 20-watt S-band transmitter using two traveling-wave tubes . A two-axis steerable high-gain parabolic antenna

935-487: A month and returning images used for landing site selection, the orbiters and landers detached; the landers then entered the Martian atmosphere and soft-landed at the sites that had been chosen. The Viking 1 lander touched down on the surface of Mars on July 20, 1976, more than two weeks before Viking 2 ' s arrival in orbit. Viking 2 then successfully soft-landed on September 3. The orbiters continued imaging and performing other scientific operations from orbit while

SECTION 10

#1732779627241

1020-513: A pair of identical American space probes , Viking 1 and Viking 2 , which landed on Mars in 1976. The mission effort began in 1968 and was managed by the NASA Langley Research Center. Each spacecraft was composed of two main parts: an orbiter designed to photograph the surface of Mars from orbit , and a lander designed to study the planet from the surface. The orbiters also served as communication relays for

1105-422: A six-sided aluminium base with alternate 1.09 and 0.56 m (43 and 22 in) long sides, supported on three extended legs attached to the shorter sides. The leg footpads formed the vertices of an equilateral triangle with 2.21 m (7.3 ft) sides when viewed from above, with the long sides of the base forming a straight line with the two adjoining footpads. Instrumentation was attached inside and on top of

1190-439: A total of 34,800 solar cells and produced 620 W of power at Mars. Power was also stored in two nickel-cadmium 30- A·h batteries . The combined area of the four panels was 15 square meters (160 square feet), and they provided both regulated and unregulated direct current power; unregulated power was provided to the radio transmitter and the lander. Two 30-amp·hour, nickel-cadmium, rechargeable batteries provided power when

1275-454: Is about 2,050 km (1,270 mi) (slightly less than the length of Greenland). The quadrangle covers an approximate area of 4.9 million square km, or a little over 3% of Mars' surface area. The Phoenix lander's landing site (68.22° N, 234.25° E) lies about 186 km (116 mi) north of the northeastern quarter of the Diacria quadrangle. The landscape viewed by the Phoenix lander

1360-488: Is located at the northwestern edge of the Tharsis volcanic plateau. Topographic, volcanic, and tectonic features associated with the large volcanoes Olympus Mons (south of map area) and Alba Mons (east of map area) characterize the southeastern and east central portions of the quadrangle. The northern and western areas of the quadrangle lie in the northern lowland plains of Mars and cover portions of Amazonis Planitia (in

1445-405: Is partially covered by volcanic deposits from Alba Mons in the east, geologically young basaltic lava flows or sediments in the west and southeast, and the jumbled, furrowed terrain of Lycus Sulci in the south. Lycus Sulci (24.6° N, 219° E) is the name applied to the northwestern portion of a larger terrain feature that partially encircles Olympus Mons and extends up to 750 km from

1530-594: Is possible from 2019 onwards. The Viking 1 lander was found to be about 6 kilometers from its planned landing site by the Mars Reconnaissance Orbiter in December 2006. Each Viking lander carried a tiny dot of microfilm containing the names of several thousand people who had worked on the mission. Several earlier space probes had carried message artifacts, such as the Pioneer plaque and

1615-528: Is probably representative of a large portion of the terrain in the northern Diacria quadrangle. Diacria is the name of a telescopic albedo feature located at 48° N and 190° E on Mars. The feature was named by Greek astronomer E. M. Antoniadi in 1930 after Diacria , the highlands around Marathon in north-west Attica , Greece. The name was approved by the International Astronomical Union (IAU) in 1958. The Diacria quadrangle

1700-479: Is still going. The pattern of the tracks have been shown to change every few months. The triangular depressions visible in Milankovič crater contain water ice in the straight wall that faces the pole, according to a new study. Eight sites were found with Milankovič crater being the only one in the northern hemisphere. This discovery is important because the ice lies under only a meter or two of cover. Research

1785-417: Is the largest volcanic feature on Mars. The flank has a very low slope (l° or less) and is characterized by lava flows and an outwardly radiating array of ridges and channels. Some of the channels have a drainage pattern that resembles that formed by rain water on the slopes of terrestrial volcanoes. However, many other channels on the flanks of Alba Mons were clearly formed by flowing lava. The western flank of

SECTION 20

#1732779627241

1870-455: The Phoenix lander in the form of perchlorate salts. It has been proposed that organic compounds could have been present in the soil analyzed by both Viking 1 and Viking 2 , but remained unnoticed due to the presence of perchlorate, as detected by Phoenix in 2008. Researchers found that perchlorate will destroy organics when heated and will produce chloromethane and dichloromethane ,

1955-584: The Cold War and the aftermath of the Space Race , all under the prospect of possibly discovering extraterrestrial life for the first time. The experiments had to adhere to a special 1971 directive that mandated that no single failure shall stop the return of more than one experiment—a difficult and expensive task for a device with over 40,000 parts. The Viking camera system cost $ 27.3 million to develop, or about $ 200 million in 2023 dollars. When

2040-754: The Thermal Emission Spectrometer (TES) on the Mars Global Surveyor spacecraft has allowed planetary scientists to estimate the amount of dust cover for broad swaths of the planet. In general, the Diacria quadrangle is extremely dusty, particularly in Arcadia Planitia and the region around the flank of Alba Mons and the Olympus Mons aureole in the southeastern portion of the quadrangle. A few large patches of relatively low dust cover occur in Amazonis Planitia and in

2125-466: The biology experiment and the gas chromatograph mass spectrometer. The X-ray fluorescence spectrometer was also mounted within the structure. A pressure sensor was attached under the lander body. The scientific payload had a total mass of approximately 91 kg (201 lb). The Viking landers conducted biological experiments designed to detect life in the Martian soil (if it existed) with experiments designed by three separate teams, under

2210-711: The cartographic quadrangles of the Martian atlas. This article about a location in Ancient Attica is a stub . You can help Misplaced Pages by expanding it . Diacria quadrangle 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 (120° to 180° west longitude) and 30° to 65° north latitude. The quadrangle uses

2295-420: The 1970s show that large portions of Arcadia Planitia have an overall mottled (blotchy light and dark) appearance. At higher resolution, landforms commonly consist of lobate flow fronts; small channel segments; wrinkle ridges ; pedestal craters ; and low, isolated volcano-like hills with summit craters. MOLA images reveal numerous large, shallowly buried craters, suggesting that an old cratered surface lies under

2380-509: The Imaging system design was completed, it was difficult to find anyone who could manufacture its advanced design. The program managers were later praised for fending off pressure to go with a simpler, less advanced imaging system, especially when the views rolled in. The program did however save some money by cutting out a third lander and reducing the number of experiments on the lander. Overall NASA says that $ 1 billion in 1970s dollars

2465-420: The atmosphere. The water returns to the ground at lower latitudes as deposits of frost or snow mixed with dust. The atmosphere of Mars contains a great deal of fine dust particles. Water vapor condenses on the particles, then they fall down to the ground due to the additional weight of the water coating. When ice at the top of the mantling layer goes back into the atmosphere, it leaves behind dust, which insulates

2550-434: The base, elevated above the surface by the extended legs. Each lander was enclosed in an aeroshell heat shield designed to slow the lander down during the entry phase. To prevent contamination of Mars by Earth organisms, each lander, upon assembly and enclosure within the aeroshell, was enclosed in a pressurized "bioshield" and then sterilized at a temperature of 111 °C (232 °F) for 40 hours. For thermal reasons,

2635-472: The base. From the center of this side extended the sampler arm, with a collector head, temperature sensor , and magnet on the end. A meteorology boom, holding temperature, wind direction, and wind velocity sensors extended out and up from the top of one of the lander legs. A seismometer , magnet and camera test targets , and magnifying mirror are mounted opposite the cameras, near the high-gain antenna. An interior environmentally controlled compartment held

Diacria - Misplaced Pages Continue

2720-505: The basis of their form, aspects, positions, and location amongst and apparent interaction with features thought to be rich in water ice, many researchers believed that the processes carving the gullies involve liquid water. However, this remains a topic of active research. The pictures below show examples of gullies in Diacria quadrangle. There is enormous evidence that water once flowed in river valleys on Mars. Images of curved channels have been seen in images from Mars spacecraft dating to

2805-564: The cap of the bioshield was jettisoned after the Centaur upper stage powered the Viking orbiter/lander combination out of Earth orbit. Astronomer Carl Sagan helped to choose landing sites for both Viking probes. Each lander arrived at Mars attached to the orbiter. The assembly orbited Mars many times before the lander was released and separated from the orbiter for descent to the surface. Descent comprised four distinct phases, starting with

2890-752: The detection of "extant microbial life on Mars." In addition, new findings from re-examination of the Gas Chromatograph Mass Spectrometer (GCMS) results were published in 2018. The leader of the imaging team was Thomas A. Mutch , a geologist at Brown University in Providence, Rhode Island . The camera uses a movable mirror to illuminate 12 photodiodes . Each of the 12 silicon diodes are designed to be sensitive to different frequencies of light. Several broad band diodes (designated BB1, BB2, BB3, and BB4) are placed to focus accurately at distances between six and 43 feet away from

2975-423: The direction of chief scientist Gerald Soffen of NASA. One experiment turned positive for the detection of metabolism (current life), but based on the results of the other two experiments that failed to reveal any organic molecules in the soil, most scientists became convinced that the positive results were likely caused by non-biological chemical reactions from highly oxidizing soil conditions. Although there

3060-635: The dust storm. Other global dust storms have also been observed, since that time. Research, published in January 2012 in Icarus, found that dark streaks were initiated by airblasts from meteorites traveling at supersonic speeds. The team of scientists was led by Kaylan Burleigh, an undergraduate at the University of Arizona. After counting some 65,000 dark streaks around the impact site of a group of five new craters, patterns emerged. The number of streaks

3145-629: The early 1970s with the Mariner 9 orbiter. Indeed, a study published in June 2017, calculated that the volume of water needed to carve all the channels on Mars was even larger than the proposed ocean that the planet may have had. Water was probably recycled many times from the ocean to rainfall around Mars. 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

3230-399: The edges of the Olympus Mons shield. Westward from Lycus Sulci, across the flat plains of Amazonis Planitia, lies an elongated region of knobby terrain called Erebus Montes (Erebus Mountains). The region contains hundreds of clustered to isolated hillocks that stand 500 to 1,000 m above the surrounding plains. The presence of numerous partly filled "ghost" craters in the area indicates that

3315-464: The giant shield volcano's base. This feature, called the Olympus Mons aureole, consists of several large lobes and has a distinctive corrugated or grooved surface texture. East of Olympus Mons, the aureole is partially covered by lava flows, but where it is exposed it goes by different names ( Gigas Sulci , for example). The origin of the aureole remains debated, but it was likely formed by huge landslides or gravity-driven thrust sheets that sloughed off

3400-494: The ground, and were throttleable from 276 to 2,667 newtons (62 to 600 lb f ). The hydrazine was purified in order to prevent contamination of the Martian surface with Earth microbes . The lander carried 85 kg (187 lb) of propellant at launch, contained in two spherical titanium tanks mounted on opposite sides of the lander beneath the RTG windscreens, giving a total launch mass of 657 kg (1,448 lb). Control

3485-484: The growth of organisms . The streaks appear in areas covered with dust. Much of the Martian surface is covered with dust because at more or less regular intervals dust settles out of the atmosphere covering everything. We know a lot about this dust because the solar panels of Mars rovers get covered with dust. The power of the Rovers has been saved many times by the wind, in the form of dust devils that have cleared

Diacria - Misplaced Pages Continue

3570-638: The hills represent the high-standing remnants of ancient highland crust that was inundated by lava flows and (possibly) alluvial sediments from Tharsis in the southeast and the Elysium volcanic province to the west. North and east of the Erebus Montes are low-lying plains that characterize a large part of the Diacria Quadrangle and of the Martian northern hemisphere in general. Medium resolution Mariner 9 and Viking spacecraft images from

3655-442: The ice changes directly from a solid to gaseous form. In the impact, the excess ice is broken up, resulting in an increase in surface area. Ice will sublimate much more if there is more surface area. After the ice disappears into the atmosphere, dry soil material will collapse and cause the crater diameter to become larger. Places on Mars that display expanded craters may indicate where future colonists can find water ice. Much of

3740-426: The ice evaporated (sublimed). The geologic history and origin of the northern plains are complex and still poorly understood. Many of the landforms resemble periglacial features seen on Earth, such as moraines , ice-wedged polygons , and pingos . Arcadia Planitia and Vastitas Borealis likely consist of a hodgepodge of old lava flows, ice-related features, and reworked sediments of diverse origin. Some theorize that

3825-468: The identical chlorine compounds discovered by both Viking landers when they performed the same tests on Mars. The question of microbial life on Mars remains unresolved. Nonetheless, on April 12, 2012, an international team of scientists reported studies, based on mathematical speculation through complexity analysis of the Labeled Release experiments of the 1976 Viking Mission, that may suggest

3910-529: The lander activated its three retro-engines and was released from the parachute. The lander then immediately used retrorockets to slow and control its descent, with a soft landing on the surface of Mars. At landing (after using rocket propellant) the landers had a mass of about 600 kg. Propulsion for deorbit was provided by the monopropellant hydrazine (N 2 H 4 ), through a rocket with 12 nozzles arranged in four clusters of three that provided 32 newtons (7.2 lb f ) thrust, translating to

3995-411: The lander had a mass of about 600 kg (1,300 lb) and the orbiter 900 kg (2,000 lb). The total launch mass was 2,328 kg (5,132 lb), of which 1,445 kg (3,186 lb) were propellant and attitude control gas. The eight faces of the ring-like structure were 0.457 m (18 in) high and were alternately 1.397 and 0.508 m (55 and 20 in) wide. The overall height

4080-432: The lander.  A low resolution broad band diode was named SURVEY.   There are also three narrow band low resolution diodes (named BLUE, GREEN and RED) for obtaining color images , and another three (IR1, IR2, and IR3) for infrared imagery. The cameras scanned at a rate of five vertical scan lines per second, each composed of 512 pixels. The 300 degree panorama images were composed of 9150 lines. The cameras' scan

4165-406: The landers deployed instruments on the surface. The project cost was roughly US$ 1 billion at the time of launch, equivalent to about $ 6 billion in 2023 dollars. The mission was considered successful and is credited with helping to form most of the body of knowledge about Mars through the late 1990s and early 2000s. The primary objectives of the two Viking orbiters were to transport

4250-519: The landers once they touched down. The Viking program grew from NASA 's earlier, even more ambitious, Voyager Mars program, which was not related to the successful Voyager deep space probes of the late 1970s. Viking 1 was launched on August 20, 1975, and the second craft, Viking 2 , was launched on September 9, 1975, both riding atop Titan IIIE rockets with Centaur upper stages. Viking 1 entered Mars orbit on June 19, 1976, with Viking 2 following on August 7. After orbiting Mars for more than

4335-415: The landers to Mars, perform reconnaissance to locate and certify landing sites, act as communications relays for the landers, and to perform their own scientific investigations. Each orbiter, based on the earlier Mariner 9 spacecraft, was an octagon approximately 2.5 m (8.2 ft) across. The fully fueled orbiter-lander pair had a mass of 3,527 kg (7,776 lb). After separation and landing,

SECTION 50

#1732779627241

4420-420: The northern plains were once covered by oceans or large lakes. Large impacts often create swarms of small secondary craters from the debris that is blasted out as a consequence of the impact. Studies of a type of secondary craters, called expanded craters , have given us insights into places where abundant ice may be present in the ground. Expanded craters have lost their rims, this may be because any rim that

4505-552: The northwest corner of the quadrangle. Many areas on Mars, including the Diacria quadrangle, experience the passage of giant dust devils . When a dust devil goes by it blows away the coating of dust and exposes the underlying dark surface. Dust devils have been seen from the ground and high overhead from orbit. They have even blown the dust off of the solar panels of the two Rovers on Mars, thereby greatly extending their lives. The twin Rovers were designed to last for three months; instead they both lasted more than six years, and one

4590-485: The northwest, with the highest elevation about 3.5 km (2.2 mi) above datum (Mars "sea level") on the western flank of the Alba Mons volcano in the southeastern portion of the quadrangle. The lowest points in the quadrangle are about 4.5 km below datum (-4,500 m) in Vastitas Borealis in the northwest corner. The regional relief is thus about 8 km, but at a local scale, slopes are very shallow;

4675-466: The other side of the mountain from the city. The only level part of this district is the small plain of Marathon, open to the sea. When the astronomer E. M. Antoniadi created his 1930 encyclopedic study of Mars, La Planète Mars , he named a small greyish region in the planet's northern hemisphere after the classical Diacria. This was later adopted in the official name of the Diacria quadrangle , one of

4760-416: The panels and boosted the power. So we know that dust falls from the atmosphere frequently. It is most generally accepted that the streaks represent avalanches of dust. Streaks appear in areas covered with dust. When a thin layer of dust is removed, the underlying surface appears dark. Much of the Martian surface is covered with dust. Dust storms are frequent, especially when the spring season begins in

4845-494: The portion of Amazonis Planitia in the south central part of the quadrangle contains some of the flattest terrain on the entire planet. Unlike some other places visited on Mars with landers ( Viking and Pathfinder ), nearly all the rocks near Phoenix are small. For about as far as the camera can see, the land is flat, but shaped into polygons between 2–3 meters in diameter and is bounded by troughs that are 20 to 50 cm (8 to 20 in) deep. These shapes are due to ice in

4930-582: The remaining ice. A study reported in the journal Science in September 2009, shows that some newly formed craters have excavated clean, water ice from just below the surface in five locations on Mars. After a short time, the ice disappears, subliming into the atmosphere. The ice is only a few meters deep. The ice was confirmed with the Compact Imaging Spectrometer ( CRISM ) on board the Mars Reconnaissance Orbiter (MRO). The ice

5015-442: The soil expanding and contracting due to major temperature changes. The microscope showed that the soil on top of the polygons is composed of flat particles (probably a type of clay) and rounded particles. Also, unlike other places visited on Mars, the site has no ripples or dunes. Ice is present a few inches below the surface in the middle of the polygons, and along its edges, the ice is at least 8 inches (20 cm) deep. Pictures of

5100-558: The south), Arcadia Planitia (west central) and Vastitas Borealis (in the north). The large crater Milankovič (118.4 km in diameter) is located in the north central portion of the quadrangle at 54.7° N, 213.3° E. Elevation data from the Mars Orbital Laser Altimeter (MOLA) instrument on the Mars Global Surveyor spacecraft shows that the regional terrain slopes gently downward to

5185-416: The southeast corner of the quadrangle (37° N, 225° E) lies a southward sloping, semicircular block of ancient, heavily cratered, highland crust that is dissected by numerous, arcuate troughs ( Acheron Fossae ). The troughs are grabens, structures formed when the crust moves downward between two faults. Grabens form in areas where the crust has undergone extensional stress. The Acheron Fossae region

SECTION 60

#1732779627241

5270-470: The southern hemisphere contained branched stream networks, suggesting that rain once fell. The flanks of some volcanoes are believed to have been exposed to rainfall because they resemble those caused on Hawaiian volcanoes. Many craters look as if the impactor fell into mud. When they were formed, ice in the soil may have melted, turned the ground into mud, then flowed across the surface. Normally, material from an impact goes up, then down. It does not flow across

5355-486: The southern hemisphere. At that time, Mars is 40% closer to the Sun. The orbit of Mars is much more elliptical then the Earth's. That is the difference between the farthest point from the Sun and the closest point to the Sun is very great for Mars, but only slight for the Earth. Also, every few years, the entire planet is engulfed in a global dust storm. When NASA's Mariner 9 craft arrived there, nothing could be seen through

5440-507: The spacecraft was not facing the Sun, during launch, while performing correction maneuvers and also during Mars occultation. By discovering many geological forms that are typically formed from large amounts of water, the images from the orbiters caused a revolution in our ideas about water on Mars . Huge river valleys were found in many areas. They showed that floods of water broke through dams, carved deep valleys, eroded grooves into bedrock, and travelled thousands of kilometers. Large areas in

5525-518: The surface of Mars is covered by a thick smooth mantle that is thought to be a mixture of ice and dust. This ice-rich mantle, a few yards thick, smooths the land. Because there are few craters on this mantle, the mantle is relatively young. Changes in Mars's orbit and tilt cause significant changes in the distribution of water ice from polar regions down to latitudes equivalent to Texas. During certain climate periods water vapor leaves polar ice and enters

5610-421: The surface under the lander appear to show that the landing rockets may have exposed a layer of ice. When the ice is exposed to the Martian atmosphere it slowly sublimates . Some dust devils were observed. Polygonal patterned ground is quite common in some regions of Mars. It is commonly believed to be caused by the sublimation of ice from the ground. Sublimation is the direct change of solid ice to

5695-523: The surface, going around obstacles, as it does on some Martian craters. Regions, called " Chaotic Terrain ," seemed to have quickly lost great volumes of water, causing large channels to be formed. The amount of water involved was estimated to ten thousand times the flow of the Mississippi River . Underground volcanism may have melted frozen ice; the water then flowed away and the ground collapsed to leave chaotic terrain. Each lander comprised

5780-440: The surfaces of other planets as well as on Earth. For example, well-documented inverted topographies have been discovered on Mars . Brain terrain is common in many places on Mars. It is formed when ice sublimates along cracks. The ridges of brain terrain may contain a core of ice. Shadow measurements from HiRISE indicate the ridges are 4–5 meters high. Viking program The Viking program consisted of

5865-443: The time, which is about $ 1 billion in 2023 dollars. The most expensive single part of the program was the lander's life-detection unit, which cost about $ 60 million then or $ 400 million in 2023 dollars. Development of the Viking lander design cost $ 357 million. This was decades before NASA's "faster, better, cheaper" approach, and Viking needed to pioneer unprecedented technologies under national pressure brought on by

5950-463: The volcano also contains some NW-SE trending grabens ( Cyane Fossae ). An image from High Resolution Imaging Science Experiment ( HiRISE ) on the Mars Reconnaissance Orbiter (MRO) beautifully shows a line of rimless pit craters in Cyane Fossae. The pits may have formed by the collapse of surface materials into open fractures created as magma intruded the subsurface rock to form dikes . Near

6035-419: The walls of craters. Usually, each gully has a dendritic alcove at its head, a fan-shaped apron at its base, and a single thread of incised channel linking the two, giving the whole gully an hourglass shape. They are believed to be relatively young because they have few, if any craters. A subclass of gullies is also found cut into the faces of sand dunes which themselves considered to be quite young. On

6120-412: Was 3.29 m (10.8 ft) from the lander attachment points on the bottom to the launch vehicle attachment points on top. There were 16 modular compartments, 3 on each of the 4 long faces and one on each short face. Four solar panel wings extended from the axis of the orbiter, the distance from tip to tip of two oppositely extended solar panels was 9.75 m (32 ft). The main propulsion unit

6205-399: Was a pronouncement by NASA during the mission saying that the Viking lander results did not demonstrate conclusive biosignatures in soils at the two landing sites, the test results and their limitations are still under assessment. The validity of the positive 'Labeled Release' (LR) results hinged entirely on the absence of an oxidative agent in the Martian soil, but one was later discovered by

6290-436: Was achieved through the use of an inertial reference unit , four gyros , a radar altimeter , a terminal descent and landing radar , and the control thrusters. Power was provided by two radioisotope thermoelectric generator (RTG) units containing plutonium-238 affixed to opposite sides of the lander base and covered by wind screens. Each Viking RTG was 28 cm (11 in) tall, 58 cm (23 in) in diameter, had

6375-481: Was conducted with instruments on board the Mars Reconnaissance Orbiter (MRO). The following images are ones referred to in this study of subsurface ice sheets. Martian gullies are small, incised networks of narrow channels and their associated downslope sediment deposits, found on the planet of Mars . They are named for their resemblance to terrestrial gullies . First discovered on images from Mars Global Surveyor , they occur on steep slopes, especially on

6460-499: Was found in a total of five locations. One of the locations (Site 5) is in the Diacria quadrangle at about 46° N, 182° E (Arcadia Planitia). This discovery is significant because it shows the presence of subsurface ice at latitudes further south than expected and proves that future colonists on Mars will be able to obtain water from a wide variety of locations. The ice can be dug up, melted, and then taken apart to provide fresh oxygen and hydrogen for rocket fuel. Hydrogen

6545-430: Was greatest closer to the impact site. So, the impact somehow probably caused the streaks. Also, the distribution of the streaks formed a pattern with two wings extending from the impact site. The curved wings resembled scimitars, curved knives. This pattern suggests that an interaction of airblasts from the group of meteorites shook dust loose enough to start dust avalanches that formed the many dark streaks. At first it

6630-447: Was mounted above the orbiter bus . Propulsion was furnished by a bipropellant ( monomethylhydrazine and nitrogen tetroxide ) liquid-fueled rocket engine which could be gimballed up to 9  degrees . The engine was capable of 1,323  N (297  lbf ) thrust, providing a change in velocity of 1,480 m/s (3,300 mph). Attitude control was achieved by 12 small compressed-nitrogen jets. An acquisition Sun sensor ,

6715-452: Was mounted on a boom near one edge of the lander base. An omnidirectional low-gain S-band antenna also extended from the base. Both these antennae allowed for communication directly with the Earth, permitting Viking 1 to continue to work long after both orbiters had failed. A UHF (381 MHz) antenna provided a one-way relay to the orbiter using a 30 watt relay radio. Data storage was on

6800-506: Was once present has collapsed into the crater during expansion or, lost its ice, if composed of ice. Excess ice (ice in addition to what is in the pores of the ground) is widespread throughout the Martian mid-latitudes, especially in Arcadia Planitia . In this region, are many expanded secondary craters that probably form from impacts that destabilize a subsurface layer of excess ice, which subsequently sublimates. With sublimation

6885-521: Was slow enough that in a crew shot taken during development of the imaging system several members show up several times in the shot as they moved themselves as the camera scanned. The Viking landers used a Guidance, Control and Sequencing Computer (GCSC) consisting of two Honeywell HDC 402 24-bit computers with 18K of plated-wire memory , while the Viking orbiters used a Command Computer Subsystem (CCS) using two custom-designed 18-bit serial processors. The two orbiters cost US$ 217 million at

6970-404: Was spent on the program, which when inflation-adjusted to 2023 dollars is about $ 6 billion. The craft all eventually failed, one by one, as follows: The Viking program ended on May 21, 1983. To prevent an imminent impact with Mars the orbit of Viking 1 orbiter was raised on August 7, 1980, before it was shut down 10 days later. Impact and potential contamination on the planet's surface

7055-474: Was the powerful fuel used by the Space Shuttle main engines. Many places on Mars show dark streaks on steep slopes , such as crater walls. It seems that the youngest streaks are dark and they become lighter with age. Often they begin as a small narrow spot then widen and extend downhill for hundreds of meters. Several ideas have been advanced to explain the streaks. Some involve water , or even

7140-500: Was thought that the shaking of the ground from the impact caused the dust avalanches, but if that was the case the dark streaks would have been arranged symmetrically around the impacts, rather than being concentrated into curved shapes. Dark streaks can be seen in some of the images below. Large portions of the martian surface are blanketed with bright reddish-ochre dust. The dust particles are typically less than 40 micrometres in size and are composed of iron oxide minerals. Data from

7225-518: Was via S band (2.1 GHz). A two-axis steerable parabolic dish antenna with a diameter of approximately 1.5 m was attached at one edge of the orbiter base, and a fixed low-gain antenna extended from the top of the bus. Two tape recorders were each capable of storing 1280 megabits . A 381- MHz relay radio was also available. The power to the two orbiter craft was provided by eight 1.57 m × 1.23 m (62 in × 48 in) solar panels , two on each wing. The solar panels comprised

#240759