Mars Global Surveyor

Mars Global Surveyor (MGS) was an American robotic spacecraft developed by NASA's Jet Propulsion Laboratory and launched November 1996. Mars Global Surveyor was a global mapping mission that examined the entire planet, from the ionosphere down through the atmosphere to the surface.[2] As part of the larger Mars Exploration Program, Mars Global Surveyor performed monitoring relay for sister orbiters during aerobraking, and it helped Mars rovers and lander missions by identifying potential landing sites and relaying surface telemetry.[2]

It completed its primary mission in January 2001 and was in its third extended mission phase when, on 2 November 2006, the spacecraft failed to respond to messages and commands. A faint signal was detected three days later which indicated that it had gone into safe mode. Attempts to recontact the spacecraft and resolve the problem failed, and NASA officially ended the mission in January 2007.

Mars Global Surveyor
Mars global surveyor
Artist's conception of Mars Global Surveyor
Mission typeMars orbiter
OperatorNASA / JPL
COSPAR ID1996-062A
Websitemars.jpl.nasa.gov/mgs/
Mission duration9 years, 11 months, 26 days from launch
9 years, 1 month, 21 days (3249 sols) at Mars

En route: 10 months, 5 days
Aerobraking: 18 months, 20 days (552 sols)

Primary mission: 1 year, 9 months, 30 days (651 sols)

Extended missions:
 First: 1 year (355 sols)
 Second: 11 months (326 sols)

Relay missions:
 First: 3 years, 9 months (1,332 sols)
 Second: 33 days (32 sols)
Spacecraft properties
Launch mass1,030.5 kg (2,272 lb)
Power980 watts
Start of mission
Launch date7 November 1996, 17:00 UTC
RocketDelta II 7925
Launch siteCape Canaveral LC-17A
ContractorBoeing IDS
End of mission
Last contact2 November 2006
Orbital parameters
Reference systemAreocentric
RegimeSun-synchronous
Semi-major axis3,769 km (2,342 mi)[1]
Eccentricity0.008[1]
Periareion372.8 km (231.6 mi)[1]
Apoareion436.5 km (271.2 mi)[1]
Inclination92.9 degrees[1]
Period1.95 hours[1]
Epoch10 December 2004
Mars orbiter
Orbital insertion12 September 1997, 01:17 UTC
MSD 43972 16:29 AMT
Mars Global Surveyor - patch transparent

Objectives

Mars Global Surveyor achieved the following science objectives during its primary mission:[3]

  1. Characterize the surface features and geological processes on Mars.
  2. Determine the composition, distribution and physical properties of surface minerals, rocks and ice.
  3. Determine the global topography, planet shape, and gravitational field.
  4. Establish the nature of the magnetic field and map the crustal remnant field.
  5. Monitor global weather and the thermal structure of the atmosphere.
  6. Study interactions between Mars' surface and the atmosphere by monitoring surface features, polar caps that expand and recede, the polar energy balance, and dust and clouds as they migrate over a seasonal cycle.

Mars Global Surveyor also achieved the following goals of its extended mission:[3]

  1. Continued weather monitoring to form a continuous set of observations with NASA's Mars Reconnaissance Orbiter, which reached Mars in March 2006.
  2. Imaging of possible landing sites for the 2007 Phoenix spacecraft, and the 2011 Curiosity rover.
  3. Observation and analysis of key sites of scientific interest, such as sedimentary-rock outcrop sites.
  4. Continued monitoring of changes on the surface due to wind and ice.

Specifications

The Surveyor spacecraft, fabricated at the Lockheed Martin Astronautics plant in Denver, is a rectangular-shaped box with wing-like projections (solar panels) extending from opposite sides. When fully loaded with propellant at the time of launch, the spacecraft weighed 1,060 kg (2,337 lb). Most of Surveyor's mass lies in the box-shaped module occupying the center portion of the spacecraft. This center module is made of two smaller rectangular modules stacked on top of each other, one of which is called the equipment module and holds the spacecraft's electronics, science instruments, and the 1750A mission computer. The other module, called the propulsion module, houses Surveyor's rocket engines and propellant tanks. The Mars Global Surveyor mission cost about $154 million to develop and build and $65 million to launch. Mission operations and data analysis cost approximately $20 million/year.[4]

Scientific instruments

Mars Observer - MGSTESpic sm
TES

Five scientific instruments flew aboard Mars Global Surveyor:[5]

The Mars Orbiter Camera (MOC) science investigation used 3 instruments: a narrow angle camera that took (black-and-white) high resolution images (usually 1.5 to 12 m per pixel) and red and blue wide angle pictures for context (240 m per pixel) and daily global imaging (7.5 km per pixel). MOC returned more than 240,000 images spanning portions of 4.8 Martian years, from September 1997 and November 2006.[7] A high resolution image from MOC covers a distance of either 1.5 or 3.1 km long. Often, a picture will be smaller than this because it has been cut to just show a certain feature. These high resolution images may cover features 3 to 10 km long. When a high resolution image is taken, a context image is taken as well. The context image shows the image footprint of the high resolution picture. Context images are typically 115.2 km square with 240 m/pixel resolution.[8]

The Mars Relay antenna supported the Mars Exploration Rovers for data relay back to Earth in conjunction with the Mars Orbiter Camera's 12 MB memory buffer. In total, more than 7.6 gigabits of data were transferred this way.[9][10]

Launch and orbit insertion

The Surveyor spacecraft was launched from the Cape Canaveral Air Station in Florida on 7 November 1996 aboard a Delta II rocket. The spacecraft traveled nearly 750 million kilometers (466 million miles) over the course of a 300-day cruise to reach Mars on 11 September 1997.

Upon reaching Mars, Surveyor fired its main rocket engine for the 22-minute Mars orbit insertion (MOI) burn. This maneuver slowed the spacecraft and allowed the planet's gravity to capture it into orbit. Initially, Surveyor entered a highly elliptical orbit that took 45 hours to complete. The orbit had a periapsis of 262 km (163 mi) above the northern hemisphere, and an apoapsis of 54,026 km (33,570 mi) above the southern hemisphere.

Aerobraking

Mars gullies.800px
This image taken by Mars Global Surveyor spans a region about 1,500 m (4,921 ft) across, showing gullies on the walls of Newton Basin in Sirenum Terra. Similar channels on Earth are formed by flowing water, but on Mars the temperature is normally too cold and the atmosphere too thin to sustain liquid water. Nevertheless, many scientists hypothesize that liquid groundwater can sometimes surface on Mars, erode gullies and channels, and pool at the bottom before freezing and evaporating.

After orbital insertion, Surveyor performed a series of orbit changes to lower the periapsis of its orbit into the upper fringes of the Martian atmosphere at an altitude of about 110 km (68 mi). During every atmospheric pass, the spacecraft slowed down by a slight amount because of atmospheric resistance. The density of the Martian atmosphere at such altitudes is comparatively low, allowing this procedure to be performed without damage to the spacecraft. This slowing caused the spacecraft to lose altitude on its next pass through the orbit's apoapsis. Surveyor used this aerobraking technique over a period of four months to lower the high point of its orbit from 54,000 km (33,554 mi) to altitudes near 450 km (280 mi).

On 11 October, the flight team performed a maneuver to raise the periapsis out of the atmosphere. This suspension of aerobraking was performed because air pressure from the atmosphere caused one of Surveyor's two solar panels to bend backward by a slight amount. The panel in question was slightly damaged shortly after launch in November 1996. Aerobraking was resumed on 7 November after flight team members concluded that aerobraking was safe, provided that it occurs at a more gentle pace than proposed by the original mission plan.

Under the new mission plan, aerobraking occurred with the low point of the orbit at an average altitude of 120 km (75 mi), as opposed to the original altitude of 110 km (68 mi). This slightly higher altitude resulted in a decrease of 66 percent in terms of air resistance pressure experienced by the spacecraft. During these six months, aerobraking reduced the orbit period to between 12 and 6 hours.

From May to November 1998, aerobraking was temporarily suspended to allow the orbit to drift into the proper position with respect to the Sun. Without this hiatus, 'Surveyor' would complete aerobraking with its orbit in the wrong solar orientation. In order to maximize the efficiency of the mission, these six months were devoted to collecting as much science data as possible. Data was collected between two and four times per day, at the low point of each orbit.

Finally, from November 1998 to March 1999, aerobraking continued and shrank the high point of the orbit down to 450 km (280 mi). At this altitude, Surveyor circled Mars once every two hours. Aerobraking was scheduled to terminate at the same time the orbit drifted into its proper position with respect to the Sun. In the desired orientation for mapping operations, the spacecraft always crossed the day-side equator at 14:00 (local Mars time) moving from south to north. This geometry was selected to enhance the total quality of the science return.

Mission results

Mapping

Mars topography (MOLA dataset) with poles HiRes
High resolution topographic map of Mars based on the Mars Global Surveyor laser altimeter research led by Maria Zuber and David Smith. North is at the top. Notable features include the Tharsis volcanoes in the west (including Olympus Mons), Valles Marineris to the east of Tharsis, and Hellas basin in the southern hemisphere.
Olympus Mons aureole MOLA zoom 64
One of the big returns of MGS, was the laser altimeter maps, here is Olympus Mons and surroundings

The spacecraft circled Mars once every 117.65 minutes at an average altitude of 378 km (235 mi). It is in a near polar orbit (inclination = 93°) which is almost perfectly circular, moving from being over the south pole to being over the north pole in just under an hour. The altitude was chosen to make the orbit Sun-synchronous, so that all images that were taken by the spacecraft of the same surface features on different dates were taken under identical lighting conditions. After each orbit, the spacecraft viewed the planet 28.62° to the west because Mars had rotated underneath it. In effect, it was always 14:00 for Mars Global Surveyor as it moved from one time zone to the next exactly as fast as the Sun. After seven sols and 88 orbits, the spacecraft would approximately retrace its previous path, with an offset of 59 km to the east. This ensured eventual full coverage of the entire surface.

In its extended mission, MGS did much more than study the planet directly beneath it. It commonly performed rolls and pitches to acquire images off its nadir track. The roll maneuvers, called ROTOs (Roll Only Targeting Opportunities), rolled the spacecraft left or right from its ground track to shoot images as much as 30° from nadir. It was possible for a pitch maneuver to be added to compensate for the relative motion between the spacecraft and the planet. This was called a CPROTO (Compensation Pitch Roll Targeting Opportunity), and allowed for some very high resolution imaging by the onboard MOC (Mars Orbiting Camera).

In addition to this, MGS could shoot pictures of other orbiting bodies, such as other spacecraft and the moons of Mars.[11] In 1998 it imaged what was later called the Phobos monolith, found in MOC Image 55103.[12][13]

After analyzing hundreds of high-resolution pictures of the Martian surface taken by the orbiting Mars Surveyor spacecraft, a team of researchers found that weathering and winds on the planet create landforms, especially sand dunes, remarkably similar to those in some deserts on Earth.[14]

Results from the Mars Global Surveyor primary mission (1996–2001) were published in the Journal of Geophysical Research by M. Malin and K. Edgett.[15] Some of these discoveries are:

  • The planet was found to have a layered crust to depths of 10 km or more. To produce the layers, large amounts of material had to be weathered, transported and deposited.
Layers in a crater in Arabia

Layers in an old crater in Arabia, as seen by Mars Global Surveyor (MGS), under the MOC Public Targeting Program. Layers may form from volcanoes, the wind, or by deposition under water. The craters on the left are pedestal craters.

Schiaparelli basin crater

Layers in crater found within the Schiaparelli crater basin as seen by Mars Global Surveyor. Image from the Sinus Sabaeus quadrangle.

Layers in Monument Valley

Layers in Monument Valley. These are accepted as being formed, at least in part, by water deposition. Since Mars contains similar layers, water remains as a major cause of layering on Mars.

Buttes and layers in Aeolis

Buttes and layers in Aeolis quadrangle, as seen by Mars Global Surveyor.

  • The northern hemisphere is probably just as cratered as the southern hemisphere, but the craters are mostly buried.
  • Many features, like impact craters, were buried, then recently exhumed.
Exhumed crater in Noachis

Crater that was buried in another age and is now being exposed by erosion, as seen by the Mars Global Surveyor under the MOC Public Targeting Program. Image is located in the Noachis quadrangle.

Exhumed Lava Flows

Lava flows were once covered over, now these platy flows are being exposed.

Exhumed Crater

Crater was buried, now it is being exhumed by erosion. Image located in Ismenius Lacus quadrangle.

Exhumed Craters

The northern hemisphere appears smooth, but the craters are covered over. Here, a group of craters are partially exposed. Image located in Cebrenia quadrangle.

  • Hundreds of gullies were discovered that were formed from liquid water, possible in recent times.[16][17][18][19]
Gully in Phaethontis

Group of gullies on north wall of crater that lies west of the crater Newton (41.3047 degrees south latitude, 192.89 east longitude). Image taken by Mars Global Surveyor, MOC Public Targeting Program. Image is located in the Phaethontis quadrangle.

Gullies and tongue-shaped glacier

Gullies in a crater in Eridania quadrangle, north of the large crater Kepler. Also, features that may be remains of old glaciers are present. One, to the right, has the shape of a tongue. Picture taken under the MOC Public Targeting Program.

Kaiser Gullies

Gullies on one wall of Kaiser Crater. Gullies usually are found in only one wall of a crater.

Gullies in Gorgonum

Full color image of gullies on wall of Gorgonum Chaos. Image is located in the Phaethontis quadrangle.

  • Large areas of Mars are covered by a mantle that coats all but the very steepest slopes. The mantle is sometimes smooth, sometimes pitted. Some believe the pits are due to the escape of water through sublimation (ice changing directly to a vapor) of buried ice.
Phaethontis surface

Close up image of Phaethontis surface taken by Mars Global Surveyor, under MOC Public Targeting Program. Pits are thought to be caused by buried ice turning into a gas.

Mantle on Cliff

The mantle drapes most of the area. Note the absence of boulders on the cliff face. An area that shows the edges of the mantle is circled. Image located in Ismenius Lacus quadrangle.

Mantle material from MGS

Mantle material, as seen by MGS.

Steep cliff in Ismenius Lacus taken with MGS

Steep cliff in Ismenius Lacus quadrangle with smooth mantle covering its face. Picture taken under MOC Public Targeting Program.

  • Some areas are covered by hematite-rich material. The hematite could have been put in place by liquid water in the past.[20]
  • Dark streaks were found to be caused by giant dust devils. Dust devil tracks were observed to frequently change; some changed in just one month.[21]
Dust devil tracks in Eridania

Pattern of large and small tracks made by giant dust devils as seen by Mars Global Surveyor, under the MOC Public Targeting Program. Image is located in Eridania quadrangle.

Kepler Crater

Kepler (Martian crater) showing dust devil tracks, as seen by Mars Global Surveyor. Kepler is a large crater in the Eridania quadrangle.

Dust Devil with Labels

Dust devil, as seen by MGS.

Dust Devil with Shadow

Dust devil in action showing shadow to the right. Image located in Cebrenia quadrangle.

  • The south pole's residual cap was observed to look like Swiss cheese. The holes are generally a few meters deep. The holes get bigger each year, so this region or hemisphere may be warming.[22] Claims that this represents a global trend, however, are cherry-picking regional data versus the planetary dataset, and MOC results versus TES and radio science (see below).
South pole changes in two year period

Changes in south pole from 1999 to 2001, as seen by Mars Global Surveyor. Notice how Swiss-cheese type holes have grown in the two years.

Swiss Cheese in South

Swiss cheese terrain, as seen by MGS. Largest mesa in image is 4 meters high.

Swiss Cheese Layers

Layers in Swiss cheese terrain. There is a bright upper layer and a darker lower layer.

Swiss Cheese Terrain close-up

Close-up view of Swiss cheese terrain. Polygonal pattern was probably formed by shallow troughs.

  • The Thermal Emission Spectrometer observes in infrared, for atmospheric studies and mineralogy.[23][24][25] TES found that Mars' planetary climate has cooled since Viking,[26][27] and just about all of the surface of Mars is covered with volcanic rock.
Cerauniustholus

Ceraunius Tholus, one of many volcanoes found on Mars.

LavaFlows from MGS

Lava flows in the Tharsis quadrangle.

Young and Old Lava Flows

Image shows both young and old lava flows from the base of Olympus Mons. The flat plain is the younger flow. The older flow has channels with levees along their edges. The presence of levees is quite common in many lava flows.

Small Volcano mgs

Small volcano in Phoenicis Lacus quadrangle. Image covers a distance 1.9 mi (3.1 km) long.

  • Hundreds of house-sized boulders were found in some areas. This indicates that some materials are strong enough to hold together, even when moving downslope. Most of the boulders appeared in volcanic regions so they were probably from weathered from lava flows.
Boulders from MGS

House-sized boulders are scattered throughout this image.

Boulders near Volcano

These boulders are near Ascraeus Mons, a Martian volcano. Volcanoes on Mars probably form hard boulders made up of basalt that is resistant to erosion in the current environment of Mars.

  • Thousands of dark slope streaks were observed. Most scientists believe they result from the avalanching of dust.[28] However, some researchers think that water may be involved.[29][30][31]
Changes in Slope Streaks

Many streaks underwent changes during the many years that MGS functioned.

Tikonravev Crater Floor

Tikonravev Crater floor, as seen by Mars Global Surveyor. Click on image to see dark slope streaks and layers. Tikonravev Crater is in the Arabia quadrangle.

Dark streaks in Diacria

Dark streaks in Diacria quadrangle, as seen by Mars Global Surveyor, under the MOC Public Targeting Program.

The Lense–Thirring test

Data from MGS have been used to perform a test of the general relativistic Lense–Thirring precession which consists of a small precession of the orbital plane of a test particle moving around a central, rotating mass such as a planet. The interpretation of these results has been debated.[32][33]

Discovery of water ice on Mars

Nanedi channel
Inner channel on floor of Nanedi Valles that suggests that water flowed for a fairly long period. Image from Lunae Palus quadrangle.

On 6 December 2006 NASA released photos of two craters in Terra Sirenum and Centauri Montes which appear to show the presence of flowing water on Mars at some point between 1999 and 2001. The pictures were produced by Mars Global Surveyor and are quite possibly the spacecraft's final contribution to our knowledge of Mars and the question of whether water exists on the planet.[34][35]

Hundreds of gullies were discovered that were formed from liquid water, possible in recent times. These gullies occur on steep slopes and mostly in certain bands of latitude.[28]

A few channels on Mars displayed inner channels that suggest sustained fluid flows. The most well-known is the one in Nanedi Valles. Another was found in Nirgal Vallis.[28]

Mission timeline

  • 7 November 1996: Launch from Cape Canaveral.
  • 11 September 1997: Arrival at Mars, began orbit insertion.
  • 1 April 1999: Primary mapping phase began.
  • 1 February 2001: First extended mission phase began.
  • 1 February 2002: Second extended mission phase began.
  • 1 January 2003: Relay mission began.
  • 30 March 2004: Surveyor photographed the Mars Exploration Rover Spirit along with its wheel tracks showing its first 85 sols of travel.
  • 1 December 2004: Science and Support mission began.
  • April 2005: MGS became the first spacecraft to photograph another spacecraft in orbit around a planet other than Earth when it captured two images of the Mars Odyssey spacecraft and one image of the Mars Express spacecraft.[36]
  • 1 October 2006: Extended mission phase began for another two years.[37]
  • 2 November 2006: Spacecraft suffers an error while attempting to reorient a solar panel and communication was lost.
  • 5 November 2006: Weak signals were detected, indicating the spacecraft was awaiting instructions. The signal cut out later that day.[38]
  • 21 November 2006: NASA announces the spacecraft has likely finished its operating career.
  • 6 December 2006: NASA releases imagery taken by MGS of a newly found gully deposit, suggesting that water still flows on Mars.
  • 13 April 2007: NASA releases its Preliminary Report on the cause(s) of MGS' loss of contact.[39]

Loss of contact

On 2 November 2006, NASA lost contact with the spacecraft after commanding it to adjust its solar panels. Several days passed before a faint signal was received indicating that the spacecraft had entered safe mode and was awaiting further instructions.[39][40]

On 20 November 2006, the Mars Reconnaissance Orbiter spacecraft attempted to image Mars Global Surveyor to verify the orientation of the spacecraft.[41] The effort was unsuccessful.

On 21 November and 22, 2006, Mars Global Surveyor failed to relay communications to the Opportunity rover on the surface of Mars. In response to this complication, Mars Exploration Program manager Fuk Li stated, "Realistically, we have run through the most likely possibilities for re-establishing communication, and we are facing the likelihood that the amazing flow of scientific observations from Mars Global Surveyor is over."[42]

On 13 April 2007, NASA announced the loss of the spacecraft was caused by a flaw in a parameter update to the spacecraft's system software.[39] The spacecraft was designed to hold two identical copies of the system software for redundancy and error checking. Subsequent updates to the software encountered a human error when two independent operators updated separate copies with differing parameters. This was followed by a corrective update that unknowingly included a memory fault which resulted in the loss of the spacecraft.

Previously, in November 2005, two operators had changed unknowingly, the same parameter on separate copies of the system software. Each operator had used a slightly different precision when inputting a parameter, which resulted in a small but significant difference in the two copies. A subsequent memory readout revealed this inconsistency to the mission's team.
In order to correct the error, an update was drafted in June 2006. However, two memory addresses were incorrectly handled in the update, which could allow values to be written into the wrong memory addresses and further complications with the mission. Five months later, the problematic memory addresses were called, resulting in the solar arrays being driven until they hit a hard stop and became unmovable. The complication led the spacecraft to incorrectly diagnose a failure of a gimbal motor causing the spacecraft to rotate to allow the unmovable solar array to point toward the Sun. However, in this position the remaining usable battery was also directed toward the Sun, resulting in the battery overheating and eventually failing. The spacecraft subsequently went into safe mode and contact with the spacecraft was lost.[39][43]

Originally, the spacecraft was intended to observe Mars for 1 Martian year (approximately 2 Earth years). However, based on the vast amount of valuable science data returned, NASA extended the mission three times. The MGS remains in a stable near-polar circular orbit at about 450 km altitude, and will crash onto the surface of the planet in about 2047.[44][45]

Other pictures

Mars Global Surveyor 1

Image of possible CO
2
geysers
, taken by Mars Global Surveyor and released on 16 October 2000.

M1501228a

Surface of Mars taken by Mars Global Surveyor.

M1501228b

Surface of Mars taken by Mars Global Surveyor.

Moc2 166a msss

Surface of Mars taken by Mars Global Surveyor on 10 August 1999.

Moc2 166b msss

Surface of Mars taken by Mars Global Surveyor on 10 August 1999.

Cratere Bonneville Rover Spirit

The Mars rover Spirit's landing site and tracks taken by Mars Global Surveyor.

PIA07944 Mars Express Seen by Mars Global Surveyor, Figure 1

The Mars Express spacecraft image taken by Mars Global Surveyor.

Mgs odyssey

The Mars Odyssey spacecraft image taken by Mars Global Surveyor.

Coprates layers

Layers in the canyon wall in Coprates quadrangle, as seen by Mars Global Surveyor, under MOC Public Targeting Program.

Banded terrain in Hellas

Banded or taffy-pull terrain in Hellas, as seen by Mars Global Surveyor. Origin is unknown at present.

Lava flow in Elysium

Lava flow in Elysium. There are many lava flows in the Elysium quadrangle. In this one, the lava flowed toward the upper right. Image taken by Mars Global Surveyor, under the MOC Public Targeting Program.

Bright rays in Memnonia

Bright rays caused by impact throwing out a bright lower layer. Some bright layers contain hydrated minerals. Picture taken by Mars Global Surveyor. Location is Memnonia quadrangle.

PIA05229 label

Mars Global Surveyor photograph of Opportunity rover's landing site showing "hole in one."

Inverted channelsmgs

Inverted channels in Aeolis quadrangle. It is believed that stream channels became raised features after coarse materials were deposited and cemented.

Delta on Mars

Picture probably is of a delta that formed in a huge lake. The area is of great interest to geologists. Evidence of past microbial life may be found in this location.

Pavonis Mons mgs

Pavonis Mons, located on the equator in Tharsis quadrangle.

See also

Monolith55103h-crop
The Phobos monolith (right of center) as taken by Mars Global Surveyor (MOC Image 55103) in 1998.

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External links

Angustus Labyrinthus

Angustus Labyrinthus is a complex of intersecting valleys or ridges near the Martian south pole (in the Mare Australe quadrangle), located at 81.68° S and 63.25° W. It was nicknamed the "Inca City" by NASA scientists due to its superficial resemblance to a ruined city. Like other formations in the area, the name 'Angustus' derives from a name given by Eugene Antoniadi in 1930 to an albedo feature that corresponds with the area. The name was approved in 2006.Angustus Labyrinthus was discovered by the Mariner 9 probe, which photographed a small area that looked like the ruins of an ancient city. Mariner 9 team members named it the "Inca City". It looked like sand dunes that had formed from winds that blew from two different directions, but the dunes were too big. In 2002 the camera on Mars Global Surveyor revealed that the 'Inca City' was part of a large circular structure that was 86 km in diameter. So the shape meant that it was probably caused by an asteroid impact which cracked the crust. Later, magma flowed along the cracks. When the magma cooled, hard, erosion resistant walls of rock (dikes) formed. The crater was covered over, then partially exhumed. The hard walls of rock were left standing as softer surrounding material eroded away.

Brashear (Martian crater)

Brashear Crater is an impact crater in the Thaumasia quadrangle of Mars, located at 54.14 S and 119.03 W. It is 77.45 km in diameter, and was named after John A. Brashear (1840–1920), an American astronomer. The name was approved in 1973.Its nearest named craters are Porter to the northeast, Lamont some hundreds of kilometers south-southeast, Dokuchaev to the south-southwest and Hussey to the northwest, the remaining two are in the Phaethontis quadrangle.

The westernmost portion and its rim lies in the Phaethontis quadrangle and three smaller craters are situated with the southern part having a central peak. North is a partly faded unnamed crater and surrounding that east and north rim are mountains. South of the crater are a bit mountainous.

Chryse Alien

The Chryse Alien refers to a Martian crater in the Chryse Planitia, with a perceived resemblance to an "alien head".

The crater is in a 712x935 image taken by the , and indexed as PIA07304. The picture was taken by the Mars Orbiter Camera on board the Mars Global Surveyor Orbiter. The image was labelled Chryse "Alien Head" by NASA when it was published on 26 January 2004. The image was part of the Jet Propulsion Laboratory's Photojournal, for 26 January 2005.

This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows an impact crater in Chryse Planitia, not too far from the Viking 1 lander site, that to seems to resemble a bug-eyed head. The two odd depressions at the north end of the crater (the "eyes") may have formed by wind or water erosion. This region has been modified by both processes, with water action occurring in the distant past via floods that poured across western Chryse Planitia from Maja Valles, and wind action common occurrence in more recent history. This crater is located near 22.5°N, 47.9°W. The 150 meter scale bar is about 164 yards long. Sunlight illuminates the scene from the left/lower left

The image came to prominence in 2018, when it was rediscovered and proposed as evidence for life on Mars.

Juventae Chasma

Juventae Chasma is an enormous box canyon (250 km × 100 km) on Mars which opens to the north and forms the outflow channel Maja Valles. Juventae Chasma is located north of Valles Marineris in the Coprates quadrangle and cuts more than 5 km into the plains of Lunae Planum.

Liais (crater)

Liais is an impact crater in the Mare Australe quadrangle of Mars, located at 75.4°S latitude and 252.8°W longitude. It measures 132.0 kilometers in diameter and was named after Emmanuel Liais. The name was approved in 1973, by the International Astronomical Union (IAU) Working Group for Planetary System Nomenclature (WGPSN).Liais Crater displays layers on its floor. Many places on Mars show rocks arranged in layers. The study of layering on Mars greatly expanded when the Mars Global Surveyor sent back images. Rock can form layers in a variety of ways. Volcanoes, wind, or water can produce layers.

A detailed discussion of layering with many Martian examples can be found in Sedimentary Geology of Mars. A paper by Grotzinger and Milliken discusses the role of water and wind in forming layers of sedimentary rocks.

List of Mars orbiters

The following table is a list of Mars orbiters, consisting of space probes which were launched from Earth and are currently orbiting Mars. As of December 2016, there are up to fourteen known artificial satellites in Mars' orbit, six of which are active.

Lomonosov (Martian crater)

Lomonosov is a crater on Mars, with a diameter close to 150 km. It is located in the Martian northern plains. Since it is large and found close (64.9° north) to the boundary between the Mare Acidalium quadrangle and the Mare Boreum quadrangle, it is found on both maps. The topography is smooth and young in this area, hence Lomonosov is easy to spot on large maps of Mars.

The crater was named in 1973 in honour of Mikhail V. Lomonosov.

The impact that created the crater has been identified as a possible source of tsunami waves which washed the shores of an ancient ocean formerly present in the basin Vastitas Borealis.

Malin Space Science Systems

Malin Space Science Systems (or MSSS) is a San Diego, California company that designs, develops, and operates instruments to fly on unmanned spacecraft. MSSS is headed by chief scientist and CEO Michael C. Malin.

Founded in 1990, their first mission was the failed 1993 Mars Observer for which they developed and operated the Mars Observer Camera Ground Data System. After this mission they were selected to provide the main camera for Mars Global Surveyor. They also developed the cameras that were carried on Mars Polar Lander, Mars Climate Orbiter, 2001 Mars Odyssey, Mars Reconnaissance Orbiter and Phoenix lander.

One of the most successful of their instruments to date was the Mars Observer Camera (MOC), on board the Mars Global Surveyor placed into orbit around Mars in September 1997. From that date until November 2006, the MOC took more than 243,000 images of Mars, some at very high resolution. Among the MOCs notable successes was the imaging of the landing sites of the two Mars Exploration Rovers (the discarded heatshield of one of the rovers was located). Even before they landed, images from the MOC were very useful in picking the destinations of the two rovers.

After more than nine years of active duty, the Mars Global Surveyor ceased sending data back to Earth and it is now lost along with all its instruments, including the MOC.

For the Mars Reconnaissance Orbiter, launched on August 12, 2005, MSSS built the Mars Color Imager (MARCI) which takes wide angle, daily global views of Mars and the Context Imager (CTX) which has a six-metre resolution.

The Mars Science Laboratory was launched in 2011 and it carries three MSSS cameras. The MastCam is the main camera on board taking still and motion images of the surroundings. The 'HandLens Imager' is on the instrument arm and provides close up images of martian soil and rocks. Finally the Mars Descent Imager (MARDI) provided high resolution images of the ground during descent.

In December 2004, MSSS was selected to provide three cameras for the Lunar Reconnaissance Orbiter (2008) mission, under contract to Northwestern University. Recently, The MSSS has developed JunoCam for the Juno Jupiter Mission, which launched in 2011.

In July 2014, NASA announced the selection of the Mastcam-Z proposal for the upcoming Mars 2020 rover mission, to be provided by MSSS. It is an improved zoom version of the original MastCam.

Mars Orbiter Camera

The Mars Orbiter Camera and Mars Observer Camera (MOC) were scientific instruments on board the Mars Observer and Mars Global Surveyor spacecraft. The camera was built by Malin Space Science Systems (MSSS) for NASA and the cost of the whole MOC scientific investigation project was about US$ 44 million, higher than anticipated in the budget.

Mars Orbiter Laser Altimeter

The Mars Orbiter Laser Altimeter (MOLA) was one of five instruments on the Mars Global Surveyor (MGS) spacecraft, which operated in Mars orbit from September 1997 to November 2006. However, the MOLA instrument transmitted altimetry data only until June 2001. The MOLA instrument transmitted infrared laser pulses towards Mars at a rate of 10 times per second, and measured the time of flight to determine the range (distance) of the MGS spacecraft to the Martian surface. The range measurements resulted in precise topographic maps of Mars. The precision maps are applicable to studies in geophysics, geology and atmospheric circulation. MOLA also functioned as a passive radiometer, and measured the radiance of the surface of Mars at 1064 nanometers.

Orcus Patera

Orcus Patera is a region on the surface of the planet Mars first imaged by Mariner 4. It is a depression about 380 km long, 140 km wide, and about 0.5 km (500 meters) deep but with a relatively smooth floor. It has a rim up to 1.8 km high. Orcus Patera is west of Olympus Mons and east of Elysium Mons. It is about halfway between those two volcanoes, and east and north of Gale crater.

It has experienced aeolian processes, and has some small craters and graben structures. However, it is not known how the patera originally formed. Theories include volcanic, tectonic, or cratering events. A study in 2000 that incorporated new results from Mars Global Surveyor along with older Viking data, did not come out clearly in favor of either volcanic or cratering processes.Mars Express observed this region in 2005, yielding a digital terrain model and color pictures.

Phobos monolith

The Phobos monolith is a large rock on the surface of Mars's moon Phobos. It is a boulder about 85 m (279 ft) across and 90 m (300 ft) tall. A monolith is a geological feature consisting of a single massive piece of rock. Monoliths also occur naturally on Earth, but it has been suggested that the Phobos monolith may be a piece of impact ejecta. The monolith is a bright object near Stickney crater, described as a "building sized" boulder, which casts a prominent shadow. It was discovered by Efrain Palermo, who did extensive surveys of Martian probe imagery, and later confirmed by Lan Fleming, an imaging sub-contractor at NASA Johnson Space Center. Lan Fleming considered the possibility that the Phobos monolith may be artificial and not a geological feature or rock.The general vicinity of the monolith is a proposed landing site by Optech and the Mars Institute, for an unmanned mission to Phobos known as PRIME (Phobos Reconnaissance and International Mars Exploration). The PRIME mission would be composed of an orbiter and lander, and each would carry four instruments designed to study various aspects of Phobos' geology. At present, PRIME has not been funded and does not have a projected launch date. Former astronaut Buzz Aldrin has spoken about the Phobos monolith and his support for a mission to Phobos.The object appears in Mars Global Surveyor images SPS252603 and SPS255103, dated 1998. The object is unrelated to another monolith located on the surface of Mars, which NASA noted as an example of a common surface feature in that region.

Swift (Deimian crater)

Swift crater is a crater on Mars's moon Deimos. It is about 3 km (1.9 mi) in diameter. Swift crater is named after Jonathan Swift, whose 1726 book Gulliver's Travels predicted the existence of two moons of Mars. Swift crater is one of two named features on Deimos, the other being Voltaire crater. On 10 July 2006, Mars Global Surveyor took an image of Deimos from 22,985 km (14,282 mi) away showing Swift crater.

Swiss cheese features

Swiss cheese features (SCFs) are curious pits in the south polar ice cap of Mars (Mare Australe quadrangle) named from their similarity to the holes in Swiss cheese. They were first seen in 2000 using Mars Orbiter Camera imagery. They are typically a few hundred meters across and 8 metres deep, with a flat base and steep sides. They tend to have similar bean-like shapes with a cusp pointing towards the south pole, indicating that insolation is involved in their formation. The angle of the Sun probably contributes to their roundness. Near the Martian summer solstice, the Sun can remain continuously just above the horizon; as a result the walls of a round depression will receive more intense sunlight, and sublimate much more rapidly than the floor. The walls sublimate and recede, while the floor remains the same.

As the seasonal frost disappears, the pit walls appear to darken considerably relative to the surrounding terrain. The SCFs have been observed to grow in size, year by year, at an average rate of 1 to 3 meters, suggesting that they are formed in a thin layer (8m) of carbon dioxide ice lying on top of water ice. Later research with HiRISE showed that the pits are in a 1-10 meter thick layer of dry ice that is sitting on a much larger water ice cap. Pits have been observed to begin with small areas along faint fractures. The circular pits have steep walls that work to focus sunlight, thereby increasing erosion. For a pit to develop, a steep wall of about 10 cm and a length of over 5 meters is necessary.

Terby (crater)

Terby is a crater on the northern edge of Hellas Planitia, Mars. It is in the Iapygia quadrangle.The 174 km diameter crater is centered at 28°S, 73°E with an elevation of −5 km. It is named after François J. Terby. It is the site of an ancient lakebed and has clay deposits. Using data from Mars Global Surveyor, Mars Odyssey, Mars Express and Mars Reconnaissance Orbiter missions researchers believe Terby's layers were formed from sediments settling under water. Crater counts show this happened during the Noachian period. It used to be thought that Terby Crater contained a large delta. However, newer observations have led researchers to think of the layered sequence as part of a group of layers that may have extended all the across Hellas. There is no valley large enough at the northern rim of Terby to have carried the large amount of sediments necessary to produce the layers. Other details in the layers argue against Terby containing a delta. Fan deposits are some of the thickest on Mars. Hydrated minerals, including Fe/Mg phyllosilicates, have been detected in several layers.

Thermal Emission Spectrometer

The Thermal Emission Spectrometer (TES) is an instrument on board Mars Global Surveyor. TES collects two types of data, hyperspectral thermal infrared data from 6 to 50 micrometres (μm) and bolometric visible-NIR (0.3 to 2.9 μm) measurements. TES has six detectors arranged in a 2x3 array, and each detector has a field of view of approximately 3 × 6 km on the surface of Mars.

The TES instrument uses the natural harmonic vibrations of the chemical bonds in materials to determine the composition of gases, liquids, and solids.

TES identified a large (30,000 square-kilometer) area that contained the mineral olivine. Olivine was found in the Nili Fossae formation. It is thought that the ancient impact that created the Isidis basin resulted in faults that exposed the olivine. Olivine is present in many mafic volcanic rocks. In the presence of water it weathers into minerals such as goethite, chlorite, smectite, maghemite, and hematite. Olivine was also discovered in many other small outcrops within 60 degrees north and south of the equator. Olivine has also been found in the SNC (shergottite, nakhlite, and chassigny) meteorites that are generally accepted to have come from Mars. Later studies have found the olivine-rich rocks to cover over 113,000 square kilometers. That is 11 times larger than the five volcanoes on the Big Island of Hawaii.

Tractus Fossae

The Tractus Fossae are a set of troughs in the Tharsis quadrangle of Mars, located at 26° north latitude and 101.4° west longitude. They are 390 km (240 mi) long and are named after a classical albedo feature name. The term "fossae" is used to indicate large troughs when using geographical terminology related to Mars. Troughs, sometimes also called grabens, form when the crust is stretched until it breaks, which forms two breaks with a middle section moving down, leaving steep cliffs along the sides. Sometimes, a line of pits form as materials collapse into a void that forms from the stretching.

Voltaire (crater)

Voltaire is an impact crater on Mars's moon Deimos and is approximately 3 km (1.9 mi) across. Voltaire crater is named after François-Marie Arouet, a French Enlightenment writer who was better known by the pen name Voltaire, who in his 1752 short story "Micromégas" predicted that Mars had two moons. Voltaire crater is one of two named features on Deimos, the other being Swift crater. On 10 July 2006, Mars Global Surveyor took an image of Deimos from 22,985 km (14,282 mi) away showing Voltaire crater and Swift crater.

Zunil (crater)

Zunil is an impact crater near the Cerberus Fossae on Mars, with a diameter of 10.26 kilometres (6.38 miles). It is named after the town of Zunil in Guatemala. The crater is located in the Elysium quadrangle. Visible in images from the Viking 1 and Viking 2 Mars orbiters in the 1970s, Zunil was subsequently imaged at higher resolution for the first time by the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) in 2000.A ray system associated with the Zunil impact, visible in infrared images from the Mars Odyssey Thermal Emission Spectrometer (THEMIS) was later detailed by McEwen et al. (2003); prior to this, large craters with ray systems had not been seen on Mars.The debris from a recent landslide was first spotted on the south-east wall of the crater by the Mars Global Surveyor Mars Orbiter Camera (MOC) in 2003, and was subsequently imaged at higher resolution by the Mars Reconnaissance Orbiter High Resolution Imaging Science Experiment (HiRISE) in December 2006.

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