Misplaced Pages

#308691

70-445: Some landscapes look just like glaciers moving out of mountain valleys on Earth. Some have a hollowed-out appearance, looking like a glacier after almost all the ice has disappeared. What is left are the moraines—the dirt and debris carried by the glacier. The center is hollowed out because the ice is mostly gone. These supposed alpine glaciers have been called glacier-like forms (GLF) or glacier-like flows (GLF). Glacier-like forms are

140-456: A Sun-synchronous orbit , it passes over Curiosity ' s location twice per day, enabling regular contact with Earth. On February 11, 2014, mission control accelerated Odyssey ' s drift toward a morning-daylight orbit to "enable observation of changing ground temperatures after sunrise and after sunset in thousands of places on Mars". The orbital change occurred gradually until November 2015. Those observations could yield insight about

210-409: A "ring-mold" shape. Another, later idea, for their formation suggests that the impacting body goes through layers of different densities. Later, erosion could have helped shape them. It was thought that ring-mold craters could only exist in areas with large amounts of ground ice. However, with more extensive analysis of larger areas, it was found the ring mold craters are sometimes formed where there

280-410: A fan or a tail-like shape. During the winter, much frost accumulates. It freezes out directly onto the surface of the permanent polar cap, which is made of water ice covered with layers of dust and sand. The deposit begins as a layer of dusty CO 2 frost. Over the winter, it recrystallizes and becomes denser. The dust and sand particles caught in the frost slowly sink. By the time temperatures rise in

350-404: A few cm of soil. This mantle layer is called "latitude dependent mantle" because its occurrence is related to the latitude. It is this mantle that cracks and then forms polygonal ground. This cracking of ice-rich ground is predicted based on physical processes. Polygonal, patterned ground is quite common in some regions of Mars. It is commonly believed to be caused by the sublimation of ice from

420-538: A free-standing body of water. The word "oxbow" can also refer to a U-shaped bend in a river or stream, whether or not it is cut off from the main stream. In South Texas , oxbows left by the Rio Grande are called resacas . In Australia , oxbow lakes are called billabongs . An oxbow lake forms when a meandering river erodes through the neck of one of its meanders . This takes place because meanders tend to grow and become more curved over time. The river then follows

490-399: A gentle equator-facing slope and a steeper pole-facing scarp. This topographic asymmetry is probably due to differences in insolation . Scalloped depressions are believed to form from the removal of subsurface material, possibly interstitial ice, by sublimation . This process may still be happening at present. On November 22, 2016, NASA reported finding a large amount of underground ice in

560-408: A gentle equator-facing slope and is rounded. Scarps discussed here have a steep pole-facing side and have been found between 55 and 59 degrees north and south latitude Scalloped topography is common in the mid-latitudes of Mars, between 45° and 60° north and south. Scalloped topography is common in the mid-latitudes of Mars, between 45° and 60° north and south. It is particularly prominent in

630-601: A large solar event bombarded the Odyssey spacecraft on October 28, 2003. Engineers believe the most likely cause is that a computer chip was damaged by a solar particle smashing into the MARIE computer board. About 85% of images and other data from NASA's twin Mars Exploration Rovers , Spirit and Opportunity , have reached Earth via communications relay by Odyssey . The orbiter helped analyze potential landing sites for

700-497: A later and maybe more accurate term because we cannot be sure the structure is currently moving. The radial and concentric cracks visible here are common when forces penetrate a brittle layer, such as a rock thrown through a glass window. These particular fractures were probably created by something emerging from below the brittle Martian surface. Ice may have accumulated under the surface in a lens shape; thus making these cracked mounds. Ice being less dense than rock, pushed upwards on

770-400: A later return to Earth. Recurrent slope lineae are small dark streaks on slopes that elongate in warm seasons. They may be evidence of liquid water. However, there remains debate about whether water or much water is needed. Many places on Mars show rocks arranged in layers. Rock can form layers in a variety of ways. Volcanoes, wind, or water can produce layers. Layers can be hardened by

SECTION 10

#1732855595309

840-417: A map and write about why the image should be taken. If your suggestion is accepted, it may take 3 months or more to see your image. You will be sent an email telling you about your images. The emails usually arrive on the first Wednesday of the month in the late afternoon. Oxbow lakes An oxbow lake is a U-shaped lake or pool that forms when a wide meander of a river is cut off , creating

910-555: A river channel is straightened artificially to improve navigation or for flood alleviation. This occurred notably on the upper Rhine in Germany in the nineteenth century. An example of an entirely artificial waterway with oxbows is the Oxford Canal in England. When originally constructed, it had a very meandering course, following the contours of the land, but the northern part of the canal

980-628: A seasonal carbon dioxide frost that forms in early autumn and remains until late spring. Many martian dunes strongly resemble terrestrial dunes but images acquired by the High-Resolution Imaging Science Experiment on the Mars Reconnaissance Orbiter have shown that martian dunes in the north polar region are subject to modification via grainflow triggered by seasonal CO 2 sublimation , a process not seen on Earth. Many dunes are black because they are derived from

1050-419: A shorter course that bypasses the meander. The entrances to the abandoned meander eventually silt up, forming an oxbow lake. Because oxbow lakes are stillwater lakes, with no current flowing through them, the entire lake gradually silts up, becoming a bog or swamp and then evaporating completely. When a river reaches a low-lying plain, often in its final course to the sea or a lake , it meanders widely. In

1120-511: A spokesman for NASA's Jet Propulsion Laboratory stated that Odyssey could continue operating until at least 2016. This estimate has since been extended to the end of 2025. By 2008, Mars Odyssey had mapped the basic distribution of water below the shallow surface. The ground truth for its measurements came on July 31, 2008, when NASA announced that the Phoenix lander confirmed the presence of water on Mars, as predicted in 2002 based on data from

1190-610: A terrain with mesas and valleys. Some of these can be quite pretty. There is evidence that volcanoes sometimes erupt under ice, as they do on Earth at times. What seems to happen it that much ice melts, the water escapes, and then the surface cracks and collapses. These exhibit concentric fractures and large pieces of ground that seemed to have been pulled apart. Sites like this may have recently had held liquid water, hence they may be fruitful places to search for evidence of life. In places large fractures break up surfaces. Sometimes straight edges are formed and large cubes are created by

1260-495: Is because rivers with high sinuosity have larger meanders, and greater opportunity for longer lakes to form. Rivers with lower sinuosity are characterized by fewer cutoffs and shorter oxbow lakes due to the shorter distance of their meanders. Oxbow lakes serve as important wetland ecosystems. In the United States, oxbow lakes serve as the primary habitat for water tupelo and the iconic bald cypress . The numerous oxbow lakes of

1330-510: Is found in the Amazonis quadrangle and near the equator. They are formed by the action of wind on sand sized particles; hence they often point in the direction that the winds were blowing when they were formed. Because they exhibit very few impact craters they are believed to be relatively young. At certain times in the Martian, dark eruptions of gas and dust occur. Wind often blows the material into

1400-407: Is great deal of evidence that water once flowed in river valleys on Mars. Pictures from orbit show winding valleys, branched valleys, and even meanders with oxbow lakes . Some are visible in the pictures below. Streamlined shapes represent more evidence of past flowing water on Mars. Water shaped features into streamlined shapes. Many locations on Mars have sand dunes . The dunes are covered by

1470-417: Is ice-rich. It is widespread; it does not seem to have a point source. The surface appearance of some regions of Mars is due to how this unit has degraded. It is a major cause of the surface appearance of lobate debris aprons . The layering of the upper plains mantling unit and other mantling units are believed to be caused by major changes in the planet's climate. Models predict that the obliquity or tilt of

SECTION 20

#1732855595309

1540-426: Is not as much ice underground. Dust devil tracks can be very pretty. They are caused by giant dust devils removing bright colored dust from the Martian surface; thereby exposing a dark layer. Dust devils on Mars have been photographed both from the ground and high overhead from orbit. They have even blown dust off the solar panels of two Rovers on Mars, thereby greatly extending their useful lifetime. The pattern of

1610-480: Is partly downstream and partly across the river toward the convex bank. As it flows along the floor of the river, it sweeps loose material toward the convex bank. This flow of the boundary layer is significantly different from the speed and direction of the primary flow of the river, and is part of the river's secondary flow . River flood plains that contain rivers with a highly sinuous platform are populated by longer oxbow lakes than those with low sinuosity . This

1680-490: Is suggested to initiate the fracture process since ribbed upper plains are common when debris aprons come together or near the edge of debris aprons—such sites would generate compressional stresses. Cracks exposed more surfaces, and consequently more ice in the material sublimates into the planet's thin atmosphere. Eventually, small cracks become large canyons or troughs. Small cracks often contain small pits and chains of pits; these are thought to be from sublimation of ice in

1750-484: Is thought that impacts created fractures in the surface, these fractures later acted as channels for fluids. Fluids cemented the structures. With the passage of time, surrounding material was eroded away, thereby leaving hard ridges behind. Since the ridges occur in locations with clay, these formations could serve as a marker for clay which requires water for its formation. Water here could have supported life. Some places on Mars break up with large fractures that created

1820-532: The Amazon River are a favorable habitat for the giant river otter . Oxbow lakes may also be suitable locations for aquaculture . Oxbow lakes contribute to the health of a river ecosystem by trapping sediments and agricultural runoff, thereby removing them from the main river flow. However, this is destructive of the oxbow lake ecosystem itself. Oxbow lakes are also vulnerable to heavy metal contamination from industrial sources. Oxbow lakes may be formed when

1890-474: The Deuteronilus Mensae ( Ismenius Lacus quadrangle ) region, but it occurs in other places as well. The remnants consist of sets of dipping layers in craters and along mesas. Sets of dipping layers may be of various sizes and shapes—some look like Aztec pyramids from Central America. Dipping layers are common in some regions of Mars. They may be the remains of mantle layers. Another idea for their origin

1960-403: The Odyssey orbiter. The science team is trying to determine whether the water ice ever thaws enough to be available for microscopic life, and if carbon-containing chemicals and other raw materials for life are present. The orbiter also discovered vast deposits of bulk water ice near the surface of equatorial regions. Evidence for equatorial hydration is both morphological and compositional and

2030-410: The Phoenix lander uncovered chunks of ice that disappeared in a few days. In addition, HiRISE has seen fresh craters with ice at the bottom. After a time, HiRISE saw the ice deposit disappear. The upper plains unit is thought to have fallen from the sky. It drapes various surfaces, as if it fell evenly. As is the case for other mantle deposits, the upper plains unit has layers, is fine-grained, and

2100-413: The boundary layer across the floor of the bowl is inward toward the center. The primary flow might be expected to fling the dense particles to the perimeter of the bowl, but instead the secondary flow sweeps the particles toward the center. The curved path of a river around a bend makes the water's surface slightly higher on the outside of the bend than on the inside. As a result, at any elevation within

2170-405: The planet Mars . The project was developed by NASA , and contracted out to Lockheed Martin , with an expected cost for the entire mission of US$ 297 million. Its mission is to use spectrometers and a thermal imager to detect evidence of past or present water and ice, as well as study the planet's geology and radiation environment. The data Odyssey obtains is intended to help answer

HiWish program - Misplaced Pages Continue

2240-556: The Utopia Planitia region of Mars. The volume of water detected has been estimated to be equivalent to the volume of water in Lake Superior . The volume of water ice in the region were based on measurements from the ground-penetrating radar instrument on Mars Reconnaissance Orbiter , called SHARAD . From the data obtained from SHARAD, " dielectric permittivity ", or the dielectric constant was determined. The dielectric constant value

2310-680: The action of groundwater. This group of layers that are found in a crater all come from the Arabia quadrangle . This next group of layered terrain comes from the Louros Valles in the Coprates quadrangle . 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

2380-408: The bowl. Set the water into circular motion with one hand or a spoon. The dense particles quickly sweep into a neat pile in the center of the bowl. This is the mechanism that leads to the formation of point bars and contributes to the formation of oxbow lakes. The primary flow of water in the bowl is circular and the streamlines are concentric with the side of the bowl. However, the secondary flow of

2450-602: The composition of the ground and about temperature-driven processes, such as warm seasonal flows observed on some slopes, and geysers fed by spring thawing of carbon dioxide (CO 2 ) ice near Mars' poles. On October 19, 2014, NASA reported that the Mars Odyssey Orbiter, as well as the Mars Reconnaissance Orbiter and MAVEN , were healthy after the Comet Siding Spring flyby. In 2010,

2520-433: The concave bank and transporting them to the convex bank is the work of the secondary flow across the floor of the river in the vicinity of a river bend. The process of deposition of silt, sand and gravel on the convex bank is clearly illustrated in point bars . The effect of the secondary flow can be demonstrated using a circular bowl. Partly fill the bowl with water and sprinkle dense particles such as sand or rice into

2590-513: The dark volcanic rock basalt. Extraterrestrial sand seas such as those found on Mars are referred to as "undae" from the Latin for waves. Some of the targets suggested became possible sites for a Rover Mission in 2020. The targets were in Firsoff (crater) and Holden Crater . These locations were picked as two of 26 locations considered for a mission that will look for signs of life and gather samples for

2660-489: The distribution of water below the shallow surface. The orbiter also discovered vast deposits of bulk water ice near the surface of equatorial regions. By December 15, 2010, it broke the record for longest serving spacecraft at Mars, with 3,340 days of operation. Odyssey has also served as the primary means of communications for NASA's Mars surface explorers in the past decade, up to the Curiosity rover . It currently holds

2730-677: The end of 2025. In August 2000, NASA solicited candidate names for the mission. Out of 200 names submitted, the committee chose Astrobiological Reconnaissance and Elemental Surveyor, abbreviated ARES (a tribute to Ares , the Greek god of war). Faced with criticism that this name was not very compelling, and too aggressive, the naming committee reconvened. The candidate name "2001 Mars Odyssey" had earlier been rejected because of copyright and trademark concerns. However, NASA e-mailed Arthur C. Clarke in Sri Lanka, who responded that he would be delighted to have

2800-429: The example below, only part of the crater is visible. if the crater came after the layered feature, it would have removed part of the feature and we would see the entire crater. To suggest a location for HiRISE to image visit the site at http://www.uahirise.org/hiwish In the sign up process you will need to come up with an ID and a password. When you choose a target to be imaged, you have to pick an exact location on

2870-533: The fractures. So-called "rootless cones" are caused by explosions of lava with ground ice under the flow. The ice melts and turns into a vapor that expands in an explosion that produces a cone or ring. Featureslike these are found in Iceland, when lavas cover water-saturated substrates. Some features look like volcanoes. Some of them may be mud volcanoes where pressurized mud is forced upward forming cones. These features may be places to look for life as they bring to

HiWish program - Misplaced Pages Continue

2940-763: The ground. Sublimation is the direct change of solid ice to 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. HiRISE images taken under the HiWish program found triangular shaped depressions in Milankovic Crater that researchers found contain vast amounts of ice that are found under only 1–2 meters of soil. These depressions contain water ice in

3010-421: The ground. Large areas of the Martian surface are loaded with ice that is protected by a meters thick layer of dust and other material. However, if cracks appear, a fresh surface will expose ice to the thin atmosphere. In a short time, the ice will disappear into the cold, thin atmosphere in a process called sublimation. Dry ice behaves in a similar fashion on the Earth. On Mars sublimation has been observed when

3080-474: The mission named after his books, and he had no objections. On September 20, NASA associate administrator Ed Weiler wrote to the associate administrator for public affairs recommending a name change from ARES to 2001 Mars Odyssey . Peggy Wilhide then approved the name change. The three primary instruments Odyssey uses are the: Mars Odyssey launched from Cape Canaveral on April 7, 2001, and arrived at Mars about 200 days later on October 24. Upon arrival,

3150-474: The mission to be launched on a Delta II 7925 launch vehicle, rather than a larger, more expensive launcher. Aerobraking ended in January 2002, and Odyssey began its science mapping mission on February 19, 2002. Odyssey ' s original, nominal mission lasted until August 2004, but repeated mission extensions have kept the mission active. The payload's MARIE radiation experiment stopped taking measurements after

3220-441: The plumes are 20–80 meters high. Dark channels can sometimes be seen; they are called "spiders". The surface appears covered with dark spots when this process is occurring. Many ideas have been advanced to explain these features. These features can be seen in some of the pictures below. Remnants of a 50–100 meter thick mantling, called the upper plains unit, has been discovered in the mid-latitudes of Mars. First investigated in

3290-408: The polygons common on many surfaces suggest ice-rich soil. High levels of hydrogen (probably from water) have been found with Mars Odyssey . Thermal measurements from orbit suggest ice. The Phoenix (spacecraft) discovered water ice with made direct observations since it landed in a field of polygons. In fact, its landing rockets exposed pure ice. Theory had predicted that ice would be found under

3360-414: The processes carving the gullies involve liquid water. However, this remains a topic of active research. Much of the Martian surface is covered with a thick ice-rich, mantle layer that has fallen from the sky a number of times in the past. In some places a number of layers are visible in the mantle. It fell as snow and ice-coated dust. There is good evidence that this mantle is ice-rich. The shapes of

3430-459: The question of whether life once existed on Mars and create a risk-assessment of the radiation that future astronauts on Mars might experience. It also acts as a relay for communications between the Curiosity rover , and previously the Mars Exploration Rovers and Phoenix lander , to Earth . The mission was named as a tribute to Arthur C. Clarke , evoking the name of his and Stanley Kubrick 's 1968 film 2001: A Space Odyssey . Odyssey

3500-563: The record for the longest-surviving continually active spacecraft in orbit around a planet other than Earth, ahead of the Pioneer Venus Orbiter (served 14 years ) and the Mars Express (serving over 20 years), at 23 years, 1 month and 5 days. As of October 2019 it is in a polar orbit around Mars with a semi-major axis of about 3,800 km or 2,400 miles. It is estimated to have enough propellant to function until

3570-411: The region of Utopia Planitia in the northern hemisphere and in the region of Peneus and Amphitrites Patera in the southern hemisphere. Such topography consists of shallow, rimless depressions with scalloped edges, commonly referred to as "scalloped depressions" or simply "scallops". Scalloped depressions can be isolated or clustered and sometimes seem to coalesce. A typical scalloped depression displays

SECTION 50

#1732855595309

3640-431: The river, water pressure is slightly greater near the outside of the bend than on the inside. A pressure gradient toward the convex bank provides the centripetal force necessary for each parcel of water to follow its curved path. The boundary layer that flows along the river floor does not move fast enough to balance the pressure gradient laterally across the river. It responds to this pressure gradient, and its velocity

3710-493: The rotational axis has varied from its present 25 degrees to maybe over 80 degrees over geological time. Periods of high tilt will cause the ice in the polar caps to be redistributed and change the amount of dust in the atmosphere. Linear ridge networks are found in various places on Mars in and around craters. Ridges often appear as mostly straight segments that intersect in a lattice-like manner. They are hundreds of meters long, tens of meters high, and several meters wide. It

3780-564: The rovers and performed the same task for NASA's Phoenix mission , which landed on Mars in May 2008. Odyssey aided NASA's Mars Reconnaissance Orbiter , which reached Mars in March 2006, by monitoring atmospheric conditions during months when the newly arrived orbiter used aerobraking to alter its orbit into the desired shape. Odyssey is in a Sun-synchronous orbit , which provides consistent lighting for its photographs. On September 30, 2008 (sol 2465)

3850-644: The spacecraft altered its orbit to gain better sensitivity for its infrared mapping of Martian minerals. The new orbit eliminated the use of the gamma ray detector, due to the potential for overheating the instrument at the new orbit. The orbiter's orientation is controlled by a set of three reaction wheels and a spare. When one failed in June 2012, the fourth was spun up and successfully brought into service. Since July 2012, Odyssey has been back in full, nominal operation mode following three weeks of 'safe' mode on remote maintenance. Mars Odyssey ' s THEMIS instrument

3920-551: The spacecraft's main engine fired in order to decelerate, which allowed it to be captured into orbit around Mars. Odyssey then spent about 76 days aerobraking , using aerodynamic drag from the upper reaches of the Martian atmosphere to gradually slow down and reduce and circularize its orbit. By planning to use the atmosphere of Mars to slow the spacecraft in its orbit rather than firing its engine or thrusters, Odyssey did not need an additional 200 kilograms (440 lb) of propellant on board. This reduction in spacecraft weight allowed

3990-415: The spring, the frost layer has become a slab of semi-transparent ice about 3 feet thick, lying on a substrate of dark sand and dust. This dark material absorbs light and causes the ice to sublimate (turn directly into a gas). Eventually much gas accumulates and becomes pressurized. When it finds a weak spot, the gas escapes and blows out the dust. Speeds can reach 100 miles per hour. Calculations show that

4060-544: The straight wall that faces the pole, according to the study published in the journal Science. Eight sites were found with Milankovic Crater being the only one in the northern hemisphere. Research 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. These triangular depressions are similar to those in scalloped terrain. However scalloped terrain, displays

4130-402: The surface and generated these spider web-like patterns. A similar process creates similar sized mounds in arctic tundra on Earth. Such features are called "pingos", an Inuit word. Pingos would contain pure water ice; thus they could be sources of water for future colonists of Mars. Many features that look like the pingos on the Earth are found in Utopia Planitia (~35-50° N; ~80-115° E). There

4200-415: The surface possible life that has been protected from radiation. Strange terrain was discovered on parts of the floor of Hellas Planitia. Scientists are not sure of how it formed. Exhumed craters seem to be in the process of being uncovered. It is believed that they formed, were covered over, and now are being exhumed as material is being eroded. When a crater forms, it will destroy what is under it. In

4270-465: The surrounding area. This means that hundreds of meters of material were eroded away. The result is that both the crater and its ejecta blanket stand above the surroundings. Pedestal craters were first observed during the Mariner missions. Ring mold craters are believed to be formed from asteroid impacts into ground that has an underlying layer of ice. The impact produces an rebound of the ice layer to form

SECTION 60

#1732855595309

4340-542: The tracks has been shown to change every few months. A study that combined data from the High Resolution Stereo Camera (HRSC) and the Mars Orbiter Camera (MOC) found that some large dust devils on Mars have a diameter of 700 metres (2,300 ft) and last at least 26 minutes. Yardangs are common in some regions on Mars, especially in what is called the " Medusae Fossae Formation ". This formation

4410-511: The two neighboring concave banks is finally cut through, either by lateral erosion of the two concave banks or by the strong currents of a flood . When this happens a new, straighter river channel develops—and an abandoned meander loop, called a cutoff , forms. When deposition finally seals off the cutoff from the river channel, an oxbow lake forms. This process can occur over a time from a few years to several decades, and may sometimes become essentially static. Gathering of erosion products near

4480-456: The vicinity of a river bend, deposition occurs on the convex bank (the bank with the smaller radius). In contrast, both lateral erosion and undercutting occur on the cut bank or concave bank (the bank with the greater radius). Continuous deposition on the convex bank and erosion of the concave bank of a meandering river cause the formation of a very pronounced meander with two concave banks getting closer. The narrow neck of land between

4550-471: 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. On 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

4620-450: Was consistent with a large concentration of water ice. A pedestal crater is a crater with its ejecta sitting above the surrounding terrain and thereby forming a raised platform (like a pedestal ). They form when an impact crater ejects material which forms an erosion-resistant layer, thus causing the immediate area to erode more slowly than the rest of the region. Some pedestals have been accurately measured to be hundreds of meters above

4690-411: Was launched April 7, 2001, on a Delta II rocket from Cape Canaveral Air Force Station , and reached Mars orbit on October 24, 2001, at 02:30 UTC (October 23, 19:30 PDT , 22:30 EDT ). On May 28, 2002 (sol 210), NASA reported that Odyssey ' s GRS instrument had detected large amounts of hydrogen , a sign that there must be ice lying within a meter of the planet's surface, and proceeded to map

4760-560: Was presented at 55th LPSC (2024) by an international team of researchers. They suggest that the layers are from past ice sheets. This unit also degrades into brain terrain . Brain terrain is a region of maze-like ridges 3–5 meters high. Some ridges may consist of an ice core, so they may be sources of water for future colonists. Some regions of the upper plains unit display large fractures and troughs with raised rims; such regions are called ribbed upper plains. Fractures are believed to have started with small cracks from stresses. Stress

4830-485: Was straightened out between 1829 and 1834, reducing its length from approximately 146 to 125 km (91 to 77 + 1 ⁄ 2  mi) and creating a number of oxbow-shaped sections isolated from the new course. There has also been a possible oxbow lake postulated in Saraswati Flumen near Ontario Lacus on Saturn's moon Titan . Mars Odyssey 2001 Mars Odyssey is a robotic spacecraft orbiting

4900-517: Was used to help select a landing site for the Mars Science Laboratory (MSL). Several days before MSL's landing in August 2012, Odyssey ' s orbit was altered to ensure that it would be able to capture signals from the rover during its first few minutes on the Martian surface. Odyssey also acted as a relay for UHF radio signals from the (MSL) rover Curiosity . Because Odyssey is in

#308691