Mars Reconnaissance Orbiter

Mars Reconnaissance Orbiter

Conceptual image depicting the Mars Reconnaissance Orbiter in an elliptical low-planet orbit around Mars
Operator	NASA / JPL
Major contractors	Lockheed Martin Space Systems University of Arizona Applied Physics Laboratory Italian Space Agency Malin Space Science Systems,
Mission type	Orbiter
Satellite of	Mars
Orbital insertion date	2006-03-10 21:24:00 UTC
Launch date	2005-08-12 11:43:00 UTC
Carrier rocket	Atlas V-401
Launch site	Space Launch Complex 41 Cape Canaveral Air Force Station
Mission duration	Primary mission: >2 years elapsed: 5 years, 6 months, and 2 days
COSPAR ID	2005-029A
Homepage	http://marsprogram.jpl.nasa.gov/mro/
Mass	2,180 kilograms (4,800 lb) fueled 1,031 kilograms (2,270 lb) dry
Power	1,000.0 W
References: [1]

Mars Reconnaissance Orbiter (MRO) is a NASA multipurpose spacecraft designed to conduct reconnaissance and exploration of Mars from orbit. As MRO entered orbit it joined five other spacecraft in orbit of or on the planet including: Mars Global Surveyor, Mars Express, Mars Odyssey, and two Mars Exploration Rovers; a then record for most spacecraft operational in Mars vicinity. The US$720 million spacecraft was built by Lockheed Martin under the supervision of the Jet Propulsion Laboratory. It was launched August 12, 2005, and attained Martian orbit on March 10, 2006. In November 2006, after five months of aerobraking, it entered its final science orbit and began its primary science phase.

MRO contains a host of scientific instruments such as cameras, spectrometers, and radar, which are used to analyze the landforms, stratigraphy, minerals, and ice of Mars. It paves the way for future spacecraft by monitoring daily weather and surface conditions, studying potential landing sites, and hosting a new telecommunications system. MRO's telecommunications system will transfer more data back to Earth than all previous interplanetary missions combined, and MRO will serve as a highly capable relay satellite for future missions.^[2]

The mission is managed by the Jet Propulsion Laboratory, at California Institute of Technology, Pasadena, California, for the NASA Science Mission Directorate, Washington, D.C.

Pre-launch

MRO was one of two missions being considered for the 2003 Mars launch window; however, during the proposal process the orbiter lost against what became known as the Mars Exploration Rovers. The orbiter mission was rescheduled for launch in 2005,^[3] and NASA announced its final name, Mars Reconnaissance Orbiter, on October 26, 2000.^[4]

MRO is modeled after NASA's highly successful Mars Global Surveyor to conduct surveillance of Mars from orbit. Early specifications of the satellite included a large camera to take high resolution pictures of Mars. In this regard, Jim Garvin, the Mars exploration program scientist for NASA, proclaimed that MRO would be a "microscope in orbit".^[5] The satellite was also to include a visible-near-infrared spectrograph.

On October 3, 2001, NASA chose Lockheed Martin as the primary contractor for the spacecraft's fabrication.^[6] By the end of 2001 all of the mission's instruments were selected. There were no major setbacks during MRO's construction, and the spacecraft was moved to John F. Kennedy Space Center on May 1, 2005 to prepare it for launch.^[7]

Mission objectives

Diagram of instrumentation aboard MRO

MRO science operations were initially scheduled to last two Earth years, from November 2006 to November 2008. One of the mission's main goals is to map the Martian landscape with its high-resolution cameras in order to choose landing sites for future surface missions. The MRO played an important role in choosing the landing site of the Phoenix Lander, which explored the Martian Arctic in Green Valley.^[8] The initial site chosen by scientists was imaged with the HiRISE camera and found to be littered with boulders. After analysis with HiRISE and the Mars Odyssey's THEMIS a new site was chosen. Mars Science Laboratory, a highly maneuverable rover, will also have its landing site inspected. The MRO will also provide critical navigation data during their landings and act as a telecommunications relay.

MRO is using its on-board scientific equipment to study the Martian climate, weather, atmosphere, and geology, and to search for signs of water in the polar caps and underground. In addition, MRO is looking for the remains of the previously lost Mars Polar Lander and Beagle 2 spacecraft,^[9] and serves as the first step in setting up an internet protocol network for the planets in our solar system. After its main science operations are completed, the probe's extended mission is to be the communication and navigation system for landers and rover probes.^[10]

Launch and orbital insertion

Launch of Atlas V carrying the Mars Reconnaissance Orbiter, 11:43:00 UTC August 12, 2005

On August 12, 2005, MRO was launched aboard an Atlas V-401 rocket from Space Launch Complex 41 at Cape Canaveral Air Force Station.^[11] The Centaur upper stage of the rocket completed its burns over a fifty-six minute period and placed MRO in interplanetary transfer orbit towards Mars.^[12]

MRO cruised through interplanetary space for seven and a half months before reaching Mars. While en route most of the scientific instruments and experiments were tested and calibrated. To ensure proper orbital insertion upon reaching Mars, four trajectory correction maneuvers were planned and a fifth emergency maneuver was discussed.^[13] However, only three trajectory correction maneuvers were necessary, saving fuel for MRO's extended mission.^[14]

MRO began orbital insertion by approaching Mars on March 10, 2006, and passing above its southern hemisphere at an altitude of 370–400 km (190 mi). All six of MRO's main engines burned for 27 minutes to slow the probe from ~2,900 m/s to ~1,900 m/s (6,500 mph to 4,250 mph). The helium pressurization tank was colder than expected, which reduced the pressure in the fuel tank by about 21 kPa (3 psi). The reduced pressure caused the engine thrust to be diminished by 2%, but MRO automatically compensated by extending the burn time by 33 seconds.^[15]

Artwork of MRO aerobraking

Completion of the orbital insertion placed the orbiter in a highly elliptical polar orbit with a period of approximately 35.5 hours.^[16] Shortly after insertion, the periapsis – the point in the orbit closest to Mars – was 3,806 km from the planet's center (426 km from its surface). The apoapsis – the point in the orbit farthest from Mars – was 47,972 km from the planet's center (44,500 km from its surface).

On March 30, 2006, MRO began the process of aerobraking, a three-step procedure that cuts in half the fuel needed to achieve a lower, more circular orbit with a shorter period. First, during its first five orbits of the planet (one Earth week), MRO used its thrusters to drop the periapsis of its orbit into aerobraking altitude. This altitude depends on the thickness of the atmosphere because Martian atmospheric density changes with its seasons. Second, while using its thrusters to make minor corrections to its periapsis altitude, MRO maintained aerobraking altitude for 445 planetary orbits (about 5 Earth months) to reduce the apoapsis of the orbit to 450 km (280 mi). This was done in such a way so as to not heat the spacecraft too much, but also dip enough into the atmosphere to slow the spacecraft down. After the process was complete, MRO used its thrusters to move its periapsis out of the edge of the Martian atmosphere, August 30, 2006.^[17][18]

In September 2006 MRO fired its thrusters twice more to fine-tune its final, nearly circular orbit approximately 250 to 316 km (155 to 196 mi) above the Martian surface.^[19] The SHARAD dipole antennas were deployed on September 16. All of the scientific instruments were tested and most were turned off prior to the solar conjunction which occurred from October 7, 2006 to November 6, 2006. After the conjunction ended the "primary science phase" began.

On November 17, 2006 NASA announced the successful test of the MRO as an orbital communications relay. Using the NASA rover "Spirit" as the point of origin for the transmission, the MRO acted as a relay for transmitting data back to Earth.

Events and discoveries

Tectonic fractures within the Candor Chasma region of Valles Marineris, Mars, retain ridge-like shapes as the surrounding bedrock erodes away. This points to past episodes of fluid alteration along the fractures and reveals clues into past fluid flow and geochemical conditions below the surface.

On September 29, 2006, MRO took its first high resolution image from its science orbit. This image is said to resolve items as small as 90 cm (3 feet) in diameter.

On October 6, 2006, NASA released detailed pictures from the MRO of Victoria crater along with the Opportunity rover on the rim above it.^[20]

In November 2006, problems began to surface in the operation of two MRO spacecraft instruments. A stepping mechanism in the Mars Climate Sounder (MCS) skipped on multiple occasions resulting in a field of view that is slightly out of position. By December normal operations of the instrument was suspended, although a mitigation strategy allows the instrument to continue making most of its intended observations.^[21] Also, an increase in noise and resulting bad pixels has been observed in several CCDs of the High Resolution Imaging Science Experiment (HiRISE). Operation of this camera with a longer warm-up time has alleviated the issue. However, the cause is still unknown and may return.^[22]

HiRISE continues to return images which have enabled discoveries regarding the geology of Mars. Foremost among these is the announcement of banded terrain observations indicating the presence and action of liquid carbon dioxide or water on the surface of Mars in its recent geological past. HiRISE was able to photograph the Phoenix lander during its parachuted descent to Vastitas Borealis on May 25, 2008.

The orbiter continued to experience recurring problems in 2009, including four spontaneous resets, culminating in a four-month shut-down of the space craft from August to December.^[23] While engineers have not determined the cause of the recurrent resets, they have created new software to help troubleshoot the problem should it recur.

Instruments

Three cameras, two spectrometers and a radar are included on the orbiter along with two "science-facility instruments", which use data from engineering subsystems to collect science data. Three technology experiments will test and demonstrate new equipment for future missions.^[24] It is expected MRO will obtain about 5,000 images a year.^[25]

HiRISE (camera)

HiRISE camera structure

The High Resolution Imaging Science Experiment camera is a 0.5 m reflecting telescope, the largest ever carried on a deep space mission, and has a resolution of 1 microradian (μrad), or 0.3 m from an altitude of 300 km. In comparison, satellite images of Earth are generally available with a resolution of 0.5 m, and satellite images on Google Maps are available to 1 m.^[26] HiRISE collects images in three color bands, 400 to 600 nm (blue-green or B-G), 550 to 850 nm (red) and 800 to 1,000 nm (near infrared or NIR).^[27]

HiRISE image of the 'face' at Cydonia Mesa

Red color images are 20,264 pixels across (6 km wide), and B-G and NIR are 4,048 pixels across (1.2 km wide). HiRISE's on-board computer reads these lines in time with the orbiter's ground speed, and images are potentially unlimited in length. Practically however, their length is limited by the computer's 28 Gigabit (Gb) memory capacity, and the nominal maximum size is 20,000 × 40,000 pixels (800 megapixels) and 4,000 × 40,000 pixels (160 megapixels) for B-G and NIR images. Each 16.4 Gb image is compressed to 5 Gb before transmission and release to the general public on the HiRISE website in JPEG 2000 format.^[28][29] To facilitate the mapping of potential landing sites, HiRISE can produce stereo pairs of images from which topography can be calculated to an accuracy of 0.25 m.^[30] HiRISE was built by Ball Aerospace & Technologies Corp.

CTX (camera)

Context (CTX) Camera

The Context Camera (CTX) provides grayscale images (500 to 800 nm) with a pixel resolution of 6 m. CTX is designed to provide context maps for the targeted observations of HiRISE and CRISM, and is also used to mosaic large areas of Mars, monitor a number of locations for changes over time, and to acquire stereo (3D) coverage of key regions and potential future landing sites^[31][32]. The optics of CTX consist of a 350 mm focal length Maksutov Cassegrain telescope with a 5,064 pixel wide line array CCD. The instrument takes pictures 30 km (19 mi) wide and has enough internal memory to store an image 160 km long before loading it into the main computer.^[33] The camera was built (and is operated by) Malin Space Science Systems.

MARCI (camera)

Mars Color Imager

The Mars Color Imager (MARCI) is a wide-angle, low-resolution camera that views the surface of Mars in five visible and two ultraviolet bands. Each day, MARCI collects about 84 images and produces a global map with pixel resolutions of 1 to 10 km. This map provides a daily weather report for Mars, helps to characterize its seasonal and annual variations, and maps the presence of water vapor and ozone in its atmosphere.^[34] The camera was built (and is operated by) Malin Space Science Systems.

CRISM (spectrometer)

CRISM Instrument

The Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) instrument is a visible and near infrared (VNIR) spectrometer that is used to produce detailed maps of the surface mineralogy of Mars. It operates from 370 to 3920 nm, measures the spectrum in 544 channels (each 6.55 nm wide), and has a resolution of 18 m (59 ft) at an altitude of 300 km (190 mi). CRISM is being used to identify minerals and chemicals indicative of the past or present existence of water on the surface of Mars. These materials include iron, oxides, phyllosilicates, and carbonates, which have characteristic patterns in their visible-infrared energy.^[35]

MCS (spectrometer)

The Mars Climate Sounder (MCS) is a spectrometer with one visible/near infrared channel (0.3 to 3.0 μm) and eight far infrared (12 to 50 μm) channels. These channels were selected to measure temperature, pressure, water vapor and dust levels. MCS observes the atmosphere on the horizon of Mars (as viewed from MRO) by breaking it up into vertical slices and taking measurements within each slice in 5 km (3 mi) increments. These measurements are assembled into daily global weather maps to show the basic variables of Martian weather: temperature, pressure, humidity and dust density.^[36]

SHARAD (radar)

An artist's concept of MRO using SHARAD to "look" under the surface of Mars

MRO's Shallow Subsurface Radar (SHARAD) experiment is designed to probe the internal structure of the Martian polar ice caps. It also gathers planet-wide information about underground layers of ice, rock and possibly liquid water that might be accessible from the surface. SHARAD uses HF radio waves between 15 and 25 MHz, a range that allows it to resolve layers as thin as 7 m (23 ft) to a maximum depth of 1 km (0.6 mi). It has a horizontal resolution of 0.3 to 3 km (0.2 to 1.9 mi).^[37] SHARAD is designed to operate in conjunction with the Mars Express MARSIS, which has lower resolution but penetrates to a much greater depth. Both SHARAD and MARSIS were made by the Italian Space Agency.^[38]

Engineering instruments

In addition to its imaging equipment, MRO carries a variety of engineering instruments. The Gravity Field Investigation Package measures variations in the Martian gravitational field through variations in the spacecraft's velocity. Velocity changes are detected by measuring doppler shifts in MRO's radio signals received on Earth. The package also includes sensitive on-board accelerometers used to deduce the in situ atmospheric density of Mars during aerobraking.^[39]

The Electra is a UHF software defined radio designed to communicate with other spacecraft as they approach, land, and operate on Mars. In addition to protocol controlled inter-spacecraft data links of 1 kbit/s to 2 Mbit/s, Electra also provides Doppler data collection, open loop recording and a highly accurate timing service based on a 5e-13 USO. Doppler information for approaching vehicles can be used for final descent targeting or descent and landing trajectory recreation. Doppler information on landed vehicles will also enable scientists to accurately determine the surface location of Mars landers and rovers. The two MER spacecraft currently on Mars utilize an earlier generation UHF relay radio providing similar functions through the Mars Odyssey orbiter. The Electra radio has used the MER spacecraft to prove its functionality but it is not scheduled to provide formal relay services until the 2008 arrival of the Phoenix Mars lander. Because the Electra radio is software defined down to the modem level, new modulation, coding or protocol functions can be added or updated while the MRO spacecraft is in orbit around Mars.^[40]

The Optical Navigation Camera images the Martian moons, Phobos and Deimos, against background stars to precisely determine MRO's orbit. Although moon imaging is not mission critical, it was included as a technology test for future orbiting and landing of spacecraft.^[41] The Optical Navigation Camera was tested successfully in February and March 2006.^[42]

Engineering data

Size comparison of MRO with predecessors

Structure

Workers at Lockheed Martin Space Systems in Denver assembled the spacecraft structure and attached the instruments. Instruments were constructed at the Jet Propulsion Laboratory, the University of Arizona Lunar and Planetary Laboratory in Tucson, Arizona, Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland, the Italian Space Agency in Rome, and Malin Space Science Systems in San Diego, California.^[43] The total cost of the spacecraft was $720 million USD.^[44]

The structure is made of mostly carbon composites and aluminum-honeycombed plates. The titanium fuel tank takes up most of the volume and mass of the spacecraft and provides most of its structural integrity. The spacecraft's total mass is less than 2,180 kg (4,806 lb) with an unfueled dry mass less than 1,031 kg (2,273 lb).^[45]

Power systems

The Mars Reconnaissance Orbiter solar panel

MRO gets all of its electrical power from two solar panels, each of which can move independently around two axes (up-down, or left-right rotation). Each solar panel measures 5.35 × 2.53 m and has 9.5 m² (102 ft²) covered with 3,744 individual photovoltaic cells. Its high-efficiency triple junction solar cells are able to convert more than 26% of the sun's energy directly into electricity and are connected together to produce a total output of 32 volts. At Mars, the two panels produce 1,000 watts of power; in contrast, the panels would generate 3,000 watts in a comparable Earth orbit by being closer to the Sun.^[46]

MRO has two nickel-hydrogen rechargeable batteries used to power the spacecraft when it is not facing the sun. Each battery has an energy storage capacity of 50 ampere-hours (180 kC). The full range of the batteries cannot be used due to voltage constraints on the spacecraft, but allows the operators to extend the battery life—a valuable capability, given that battery drain is one of the most common causes of long-term satellite failure. Planners anticipate that only 40% of the batteries' capacities will be required during the lifetime of the spacecraft.^[46]

Electronic systems

MRO's main computer is a 133 MHz, 10.4 million transistor, 32-bit, RAD750 processor. This processor is a radiation-hardened version of a PowerPC 750 or G3 processor with a specially-built motherboard. The RAD750 is a successor to the RAD6000. This processor may seem underpowered in comparison to a modern PC processor, but it is extremely reliable, resilient, and can function in solar flare-ravaged deep space.^[47] The operating system software is VxWorks and has extensive fault protection protocols and monitoring.^[48]

Data is stored in a 160 Gb (20 GB) flash memory module consisting of over 700 memory chips, each with a 256 Mbit capacity. This memory capacity is not actually that large considering the amount of data to be acquired; for example, a single image from the HiRISE camera can be as large as 28 Gb.^[48]

Attitude determination

In order to determine the spacecraft's orbit and facilitate maneuvers, sixteen sun sensors – eight primaries and eight backups – are placed around the spacecraft to calibrate solar direction relative to the orbiter's frame. Two star trackers, digital cameras used to map the position of catalogued stars, provide NASA with full, three-axis knowledge of the spacecraft orientation and attitude. A primary and backup Miniature Inertial Measurement Unit (MIMU), provided by Honeywell, measures changes to the spacecraft attitude as well as any non-gravitationally induced changes to its linear velocity. Each MIMU is a combination of three accelerometers and three ring-laser gyroscopes. These systems are all critically important to MRO, as it must be able to point its camera to a very high precision in order to take the high-quality pictures that the mission requires. It has also been specifically designed to minimize any vibrations on the spacecraft, so as to allow its instruments to take images without any distortions caused by vibrations.^[49]

Telecommunications system

MRO High Gain Antenna installation

The Telecom Subsystem on MRO is the best digital communication system sent into deep space so far and for the first time using capacity achieving turbo-codes. It consists of a very large (3 meter) antenna, which is used to transmit data through the Deep Space Network via X-band frequencies at 8 GHz, and it demonstrates the use of the K_a band at 32 GHz for higher data rates. Maximum transmission speed from Mars is projected to be as high as 6 Mbit/s, a rate ten times higher than previous Mars orbiters. The spacecraft carries two 100-watt X-band amplifiers (one of which is a backup), one 35-watt Ka-band amplifier, and two Small Deep Space Transponders (SDSTs).^[2]

Two smaller low-gain antennas are also present for lower-rate communication during emergencies and special events, such as launch and Mars Orbit Insertion. These antennas do not have focusing dishes and can transmit and receive from any direction. They are an important backup system to ensure that MRO can always be reached, even if its main antenna is pointed away from the Earth.^[2]

The Ka-band subsystem is used for demonstration purposes. Due to lack of spectrum at 8.41 GHz X-band, future high-rate deep space missions will use 32 GHz Ka-band. NASA Deep Space Network (DSN) has implemented Ka-band receiving capabilities at all three of its complexes (Goldstone, Canberra and Madrid) over its 34-m beam-waveguide (BWG) antenna subnet. MRO Ka-band demonstration will demonstrate viability of Ka-band for deep space operations. During the cruise phase, spacecraft Ka-band telemetry was tracked 36 times by these antennas proving DSN Ka-band reception functionality at all the antennas. During the primary science phase, Ka-band demonstration is assigned two passes a week for Ka-band demonstration purposes. The success of Ka-band during cruise also makes it a viable backup for the X-band subsystem on MRO.

Propulsion and attitude control

Data comparison chart

The spacecraft uses a 1,175 L (310 US gal) fuel tank filled with 1187 kg (2617 lb) of hydrazine monopropellant. Fuel pressure is regulated by adding pressurized helium gas from an external tank. Seventy percent of the fuel was used for orbital insertion.^[50]

MRO has twenty rocket engine thrusters on board. Six large thrusters each produce 170 N (38 lbf) of thrust for a total of 1,020 N (230 lbf) meant mainly for orbital insertion. These thrusters were originally designed for the Mars Surveyor 2001 Lander. Six medium thrusters each produce 22 N (5 lbf) of thrust for trajectory correction maneuvers and attitude control during orbit insertion. Finally, eight small thrusters each produce 0.9 N (0.2 lbf) of thrust for attitude control during normal operations.^[50]

Four reaction wheels are also used for precise attitude control during activities requiring a highly stable platform, such as high-resolution imaging, in which even small motions can cause blurring of the image. Each wheel is used for one axis of motion. The fourth (skewed) wheel is a backup in case one of the other three wheels fails. Each wheel weighs 10 kg (22 lb) and can be spun as fast as 100 Hz or 6,000 rpm.^[50]

Discoveries and photographs

Water ice in ice cap measured

Results, published in 2009, of radar measurements of the North Polar ice cap determined that the volume of water ice in the cap is 821,000 cubic kilometers (197,000 cubic miles). That's equal to 30% of the Earth's Greenland ice sheet.^[51]

Ice exposed in new craters

Bright part is water ice that has been exposed by impact. The ice was identified using CRISM on the MRO.

Impressive research, reported in the journal Science in September 2009^[52], has showed that some new craters on Mars show exposed, pure, water ice. After a time, the ice disappears, evaporating into the atmosphere. The ice is only a few feet deep. The ice was confirmed with the Compact Imaging Spectrometer (CRISM)] onboard the Mars Reconnaissance Orbiter (MRO). The ice was found in a total of 5 locations. Three of the locations are in the Cebrenia quadrangle. These locations are 55.57° N, 150.62° E; 43.28° N, 176.9° E; and 45° N, 164.5° E. Two others are in the Diacria quadrangle: 46.7° N, 176.8° E and 46.33° N, 176.9° E.^[53][54][55] This discovery 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, then taken apart to provide fresh oxygen and hydrogen for rocket fuel. Hydrogen is the powerful fuel used by the space shuttle main engines.

Lobate debris aprons

Lobate Debris Apron in Phlegra Montes, Cebrenia quadrangle. The debris apron is probably mostly ice with a thin covering of rock debris, so it could be a source of water for future Martian colonists. Scale bar is 500 meters long.

One of the most important discoveries made by the Mars Reconnaissance Orbiter was that features called Lobate Debris Aprons (LDA's) contain large amounts of water ice. Of interest from the days of the Viking Orbiters, these LDA's are piles of material surrounding cliffs. They have a convex topography and a gentle slope; this suggests flow away from the steep source cliff. In addition, lobate debris aprons can show surface lineations just as rock glaciers on the Earth.^[56] The Shallow Radar on the Mars Reconnaissance Orbiter has provided strong evidence that the LDAs in Hellas Planitia are glaciers that are covered with a thin layer of rocks. Radar from the Mars Reconnaissance Orbiter gave a strong reflection from the top and base of LDAs, meaning that pure water ice made up the balk of the formation (between the two reflections).^[57] Based on the experiments of the Phoenix lander and the studies of the Mars Odyssey from orbit, frozen water is known to exist a just under the surface of Mars in the far north and south (high latitudes). The discovery of water ice in LDA's demonstrates that water is found at even lower latitudes. Future colonists on Mars will be able to tap into these ice deposits, instead of having to travel to much higher latitudes. Another major advantage of LDA's over other sources of Martian water is that they can easily be detected and mapped from orbit. Lobate Debris Aprons are shown below from the Phlegra Montes which are at a latitude of 38.2 degrees north. The Phoenix lander set down at about 68 degrees north latitude, so the discovery of water ice in LDA's greatly expands the range of easily available water on Mars ^[58]. It is far easier to land a spaceship near the equator of Mars, so the closer water is available to the equator the better it will be for future colonists.

Inverted relief

Inverted Stream Channels in Antoniadi Crater, as seen by HiRISE.

Some places on Mars show inverted relief. In these locations, a stream bed may be a raised feature, instead of a valley. The inverted former stream channels may be caused by the deposition of large rocks or due to cementation. In either case erosion would erode the surrounding land and leave the old channel as a raised ridge because the ridge will be more resistant to erosion. An image below, taken with HiRISE of Antoniadi Crater shows sinuous ridges that are old channels that have become inverted.^[59]

Chloride deposits

Evidence of water from chloride deposits in Phaethontis. Picture from HiRISE.

Using data from Mars Global surveyor, Mars Odyssey and the Mars Reconnaissance Orbiter, scientists have found widespread deposits of chloride minerals. A picture below shows some deposits within the Phaethontis quadrangle. Evidence suggests that the deposits were formed from the evaporation of mineral enriched waters. The research suggests that lakes may have been scattered over large areas of the Martian surface. Usually chlorides are the last minerals to come out of solution. Carbonates, sulfates, and silica should precipitate out ahead of them. Sulfates and silica have been found by the Mars Rovers on the surface. Places with chloride minerals may have once held various life forms. Furthermore, such areas should preserve traces of ancient life.^[60]

Other aqueous minerals

In a 2009 paper, a large group of scientists reported on 9-10 different classes of minerals that are formed in the presence of water. Different types of clays (also called phyllosilicates) were found in many locations. Some of the physilicates identified were aluminum smectite, iron/magnesium smectite, kaolinite, prehnite, and chlorite. Rocks containing carbonate were found around the Isidis basin. Carbonates belong to one class in which life could have developed. Areas around Valles Marineris were found to contain hydrated silica and hydrated sulfates. Hydrated sulfates and ferric minerlas were discovered in Terra Meridiani and in Valles Marineris. Other minerals found on Mars were jarosite, alunite, hematite, opal, and gypsum. Two to five of the mineral classes were formed with the right pH and the enough water to permit life to grow.^[61]

Layers

Columbus Crater contains layers, also called strata. Many places on Mars show rocks arranged in layers. Sometimes the layers are of different colors. Light-toned rocks on Mars have been associated with hydraded minerals like sulfates. The Mars Rover Opportunity examined such layers close-up with several instruments. Some layers are probably made up of fine particles because they seem to break up into fine dust. Other layers break up into large boulders so they are probably much harder. Basalt, a volcanic rock, is thought to in the layers that form boulders. Basalt has been identified on Mars in many places. Instruments on orbiting spacecraft have detected clay (also called phyllosilicates) in some layers. Scientists are excited about finding hydrated minerals such as sulfates and clays on Mars because they are usually formed in the presence of water.^[62] Places that contain clays and/or other hydrated minerals would be good places to look for evidence of life.^[63]

Rock can form layers in a variety of ways. Volcanoes, wind, or water can produce layers.^[64]

Becquerel Crater layers, as seen by HiRISE. Click on image to see fault.

Light colored layers in Eos Chaos, as seen by HiRISE.

Columbus Crater Layers, as seen by HiRISE. This false-color image is about 800 feet across. Some of the layers contain hydrated minerals.

Avalanche

On February 19, 2008, Mars Reconnaissance Orbiter photographed an avalanche as it was occurring.

Martian avalanche and debris falls (HiRISE 2008)	Image of the February 19, 2008 Mars avalanche captured by the Mars Reconnaissance Orbiter.	Closer shot of the avalanche.	Dust clouds rise above the 2,300-foot (700 m) deep cliff.
A photo with scale demonstrates the size of the avalanche.

Other spacecraft

Image of Phoenix landing on Mars, as seen by HiRISE. Although it looks like it landed in the crater, it actually landed 20 km in front of crater.

Amazing view of Phoenix Lander and its heatshield as seen by HiRISE.

Opportunity Tracks, as seen by HiRISE. The white dots are places where rover stopped to perform scientific observations or turned.

Opportunity Rover as seen by HiRISE on January 29, 2009. Opportunity is on its way to Endeavour Crater, 17 km away at this point.

Other noteworthy images

Cliff in Kasei Valles system, as seen by HiRISE.	Enlargement of cliff in Kasei Valles system in previous image showing boulders and their tracks, as seen by HiRISE. Click on image to see a boulder only 2.2 yards across (smaller than a bedroom).	Olympia Planitia Dunes, as seen by HiRISE. Gypsum has been detected here. Gypsum is usually formed in the presence of water. So this image supports large amounts of water in the past.	Wirtz Crater Dunes with ripples and frost, as seen by HiRISE.
Springs in Vernal Crater, as seen by HIRISE. Springs are thought to be one of the best places to look for life because molten rock may have kept the area warm enough to support life. Also, fossils can be easily preserved by minerals found in association with hot springs.	Star burst Channels caused by escaping gas, as seen by HiRISE. Star burst channels, also called spiders, may be about 500 meters in diameter and 1 meter deep.	New Impact that formed between March 2000 and July 2003. Scale bar is 500 meters long. Image taken with HiRISE. This is one of many impacts detected by studies with the Mars Reconnaissance Orbiter.	Alluvial Fans in Mojave Crater, as seen by HiRISE. High ground is on the right. Branched network of channels runs from higher ground (crater rim) to lower ground.

See also

• Geography of Mars
• Colonization of Mars
• Exploration of Mars
• Mars Direct
• Planetary science
• Lunar Reconnaissance Orbiter

References

Further reading

• Mishkin, Andrew (2004). Sojourner : An Insider's View of the Mars Pathfinder Mission. New York: Berkeley Books. ISBN 0-425-19199-0. 
• Squyres, Steve (2005). Roving Mars: Spirit, Opportunity, and the Exploration of the Red Planet. New York: Hyperion. ISBN 1-4013-0149-5. 
• Read, Peter L. & Lewis, Steven L. (2004). The Martian Climate Revisited: Atmosphere and Environment of a Desert Planet. Berlin: Springer. ISBN 3-540-40743-X. 
• Zubrin, Robert (1997). The Case for Mars. London: Pocket Books. ISBN 0-684-83550-9. 

External links

• Mars Reconnaissance Orbiter website at NASA
• Mars Reconnaissance Orbiter website at JPL
• Mars Reconnaissance Orbiter images at JPL
• HiRise Image Catalog. The Lunar and Planetary Laboratory at The University of Arizona
• CRISM Real Time Observations Viewer Java Application at The Johns Hopkins University Applied Physics Laboratory
• Mars Reconnaissance Orbiter Mission Profile by NASA's Solar System Exploration
• Mars Reconnaissance Orbiter Reception
• CTX website
• MARCI website
• SHARAD website
• A simulation of the arrival trajectory of the Mars Reconnaissance Orbiter
• HiBlog, the HiRISE Blog. Contains information about MRO.
• Patterns of Mars - 12 High Resolution Photos by HiRISE on www.time.com

Spacecraft missions to Mars Flybys Mariner 4 · 6 · 7 · Mars 4 · Rosetta · Dawn Orbiters Mariner 9 · Mars 2 · 3 · 5 · Viking 1 · 2 · Phobos 2 · Mars Global Surveyor · 2001 Mars Odyssey · Mars Express · Mars Reconnaissance Orbiter Landers Mars 3 · Viking 1 · 2 · Mars Pathfinder · Phoenix Rovers Sojourner · Mars Exploration Rovers (Spirit · Opportunity) Future missions Mars Science Laboratory (2011) · Fobos-Grunt / Yinghuo 1 (2011) · MetNet (2011-2019) · Northern Light (2012) · MAVEN (2013) · Mars Trace Gas Mission (2016) · ExoMars static lander (2016) and rover (2018) · Mars Astrobiology Explorer-Cacher‎ (2018) · Mars sample return mission (2018+) · Manned mission (2030+) Related topics Exploration · Colonization · Failed Mars missions · Mars Scout Program Bold italics indicate active missions

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