Exploration of Mars

The exploration of Mars is the study of Mars by spacecraft. Probes sent from Earth, beginning in the late 20th century, have yielded a dramatic increase in knowledge about the Martian system, focused primarily on understanding its geology and habitability potential.

Current status
Engineering interplanetary journeys is complicated and the exploration of Mars has experienced a high failure rate, especially the early attempts. Roughly two-thirds of all spacecraft destined for Mars failed before completing their missions and some failed before their observations could begin. Some missions have met with unexpected success, such as the twin Mars Exploration Rovers, which operated for years beyond their specification. On 15 March 2015, two scientific rovers were on the surface of Mars beaming signals back to Earth (Opportunity of the Mars Exploration Rover mission and Curiosity of the Mars Science Laboratory mission), with five orbiters surveying the planet: Mars Odyssey, Mars Express, Mars Reconnaissance Orbiter, Mars Orbiter Mission and MAVEN, which have contributed massive amounts of information about Mars. No sample return missions have been attempted for Mars and an attempted return mission for Mars' moon Phobos (Fobos-Grunt) failed.

On 24 January 2014, NASA reported that current studies on the planet Mars by the Curiosity and Opportunity rovers will search for evidence of ancient life, including a biosphere based on autotrophic, chemotrophic and/or chemolithoautotrophic microorganisms, as well as ancient water, including fluvio-lacustrine environments (plains related to ancient rivers or lakes) that may have been habitable. The search for evidence of habitability, taphonomy (related to fossils), and organic carbon on the planet Mars is now a primary NASA objective.

Martian system
Mars has long been the subject of human interest. Early telescopic observations revealed color changes on the surface that were attributed to seasonal vegetation and apparent linear features were ascribed to intelligent design. Further telescopic observations found two moons, Phobos and Deimos, polar ice caps and the feature now known as Olympus Mons, the solar system's tallest mountain. The discoveries piqued further interest in the study and exploration of the red planet. Mars is a rocky planet, like Earth, that formed around the same time, yet with only half the diameter of Earth, and a far thinner atmosphere, it has a cold and desert-like surface.

Launch windows
The minimum-energy launch windows for a Martian expedition occur at intervals of approximately two years and two months (specifically 780 days, the planet's synodic period with respect to Earth). In addition, the lowest available transfer energy varies on a roughly 16-year cycle. For example, a minimum occurred in the 1969 and 1971 launch windows, rising to a peak in the late 1970s, and hitting another low in 1986 and 1988.

Past and current missions
Starting in 1960, the Soviets launched a series of probes to Mars including the first intended flybys and hard (impact) landing (Mars 1962B). The first successful fly-by of Mars was on 14–15 July 1965, by NASA's Mariner 4. On November 14, 1971 Mariner 9 became the first space probe to orbit another planet when it entered into orbit around Mars. The amount of data returned by probes increased dramatically as technology improved.

The first to contact the surface were two Soviet probes: Mars 2 lander on November 27 and Mars 3 lander on December 2, 1971—Mars 2 failed during descent and Mars 3 about twenty seconds after the first Martian soft landing. Mars 6 failed during descent but did return some corrupted atmospheric data in 1974. The 1975 NASA launches of the Viking program consisted of two orbiters, each with a lander that successfully soft landed in 1976. Viking 1 remained operational for six years, Viking 2 for three. The Viking landers relayed the first color panoramas of Mars.

The Soviet probes Phobos 1 and 2 were sent to Mars in 1988 to study Mars and its two moons, with a focus on Phobos. Phobos 1 lost contact on the way to Mars. Phobos 2, while successfully photographing Mars and Phobos, failed before it was set to release two landers to the surface of Phobos.

Roughly two-thirds of all spacecraft destined for Mars have failed without completing their missions, and it has a reputation as a difficult space exploration target.

Missions that ended prematurely after Phobos 1 & 2 (1988) include (see Probing difficulties section for more details):
 * Mars Observer (launched in 1992)
 * Mars 96 (1996)
 * Mars Climate Orbiter (1999)
 * Mars Polar Lander with Deep Space 2 (1999)
 * Nozomi (2003)
 * Beagle 2 (2003)
 * Fobos-Grunt with Yinghuo-1 (2011)

Following the 1993 failure of the Mars Observer orbiter, the NASA Mars Global Surveyor achieved Mars orbit in 1997. This mission was a complete success, having finished its primary mapping mission in early 2001. Contact was lost with the probe in November 2006 during its third extended program, spending exactly 10 operational years in space. The NASA Mars Pathfinder, carrying a robotic exploration vehicle Sojourner, landed in the Ares Vallis on Mars in the summer of 1997, returning many images.

Phoenix landed on the north polar region of Mars on May 25, 2008. Its robotic arm dug into the Martian soil and the presence of water ice was confirmed on June 20, 2008. The mission concluded on November 10, 2008 after contact was lost. In 2008, the price of transporting material from the surface of Earth to the surface of Mars was approximately US$309,000 per kilogram.

Rosetta came within 250 km of Mars during its 2007 flyby. Dawn flew by Mars in February 2009 for a gravity assist on its way to investigate Vesta and Ceres.

Recent missions


NASA's Mars Odyssey orbiter entered Mars orbit in 2001. Odyssey's Gamma Ray Spectrometer detected significant amounts of hydrogen in the upper metre or so of regolith on Mars. This hydrogen is thought to be contained in large deposits of water ice.

The Mars Express mission of the European Space Agency (ESA) reached Mars in 2003. It carried the Beagle 2 lander, which was not heard from after being released and was declared lost in February 2004. Beagle 2 was located in January 2015 by HiRise camera on NASA’s Mars Reconnaissance Orbiter (MRO) having landed safely but failed to fully deploy its solar panels and antenna. In early 2004 the Mars Express Planetary Fourier Spectrometer team announced the orbiter had detected methane in the Martian atmosphere. ESA announced in June 2006 the discovery of aurorae on Mars.

In January 2004, the NASA twin Mars Exploration Rovers named Spirit (MER-A) and Opportunity (MER-B) landed on the surface of Mars. Both have met or exceeded all their targets. Among the most significant scientific returns has been conclusive evidence that liquid water existed at some time in the past at both landing sites. Martian dust devils and windstorms have occasionally cleaned both rovers' solar panels, and thus increased their lifespan. Spirit Rover (MER-A) was active until 2010, when it stopped sending data because it had fallen into a sand dune.

On 10 March 2006, the NASA Mars Reconnaissance Orbiter (MRO) probe arrived in orbit to conduct a two-year science survey. The orbiter began mapping the Martian terrain and weather to find suitable landing sites for upcoming lander missions. The MRO snapped the first image of a series of active avalanches near the planet's north pole, scientists said March 3, 2008.

The Mars Science Laboratory mission was launched on November 26, 2011 and it delivered the Curiosity rover, on the surface of Mars on August 6, 2012 UTC. It is larger and more advanced than the Mars Exploration Rovers, with a velocity of up to 90 meters per hour (295 feet per hour). Experiments include a laser chemical sampler that can deduce the make-up of rocks at a distance of 7 meters.

The Indian Space Research Organisation (ISRO) launched its Mars Orbiter Mission (MOM) on November 5, 2013. It was successfully inserted into Mars orbit on 24 September 2014. India's ISRO is the fourth space agency to reach Mars, after the Soviet space program, NASA and ESA. India became the first country to successfully get a spacecraft into the Martian orbit on its maiden attempt.

Overview of missions
The following entails a brief overview of Mars exploration, oriented towards orbiters and flybys; see also Mars landing and Mars rover.

1960s
Between 1960 and 1969, the Soviet Union launched nine probes intended to reach Mars. They all failed: three at launch; three failed to reach near-Earth orbit; one during the burn to put the spacecraft into trans-Mars trajectory; and two during the interplanetary orbit.

The Mars 1M programs (sometimes dubbed Marsnik in Western media) was the first Soviet unmanned spacecraft interplanetary exploration program, which consisted of two flyby probes launched towards Mars in October 1960, Mars 1960A and Mars 1960B (also known as Korabl 4 and Korabl 5 respectively). After launch, the third stage pumps on both launchers were unable to develop enough pressure to commence ignition, so Earth parking orbit was not achieved. The spacecraft reached an altitude of 120 km before reentry.

Mars 1962A was a Mars fly-by mission, launched on October 24, 1962 and Mars 1962B a intended first Mars lander mission, launched in late December of the same year (1962). Both failed from either breaking up as they were going into Earth orbit or having the upper stage explode in orbit during the burn to put the spacecraft into trans-Mars trajectory.

The first success
Mars 1 (1962 Beta Nu 1), an automatic interplanetary spacecraft launched to Mars on November 1, 1962, was the first probe of the Soviet Mars probe program to achieve interplanetary orbit. Mars 1 was intended to fly by the planet at a distance of about 11,000 km and take images of the surface as well as send back data on cosmic radiation, micrometeoroid impacts and Mars' magnetic field, radiation environment, atmospheric structure, and possible organic compounds. Sixty-one radio transmissions were held, initially at two-day intervals and later at 5 day intervals, from which a large amount of interplanetary data was collected. On 21 March 1963, when the spacecraft was at a distance of 106,760,000 km from Earth, on its way to Mars, communications ceased due to failure of its antenna orientation system.

In 1964, both Soviet probe launches, of Zond 1964A on June 4, and Zond 2 on November 30, (part of the Zond program), resulted in failures. Zond 1964A had a failure at launch, while communication was lost with Zond 2 en route to Mars after a mid-course maneuver, in early May 1965.

In 1969, and as part of the Mars probe program, the Soviet Union prepared two identical 5-ton orbiters called M-69, dubbed by NASA as Mars 1969A and Mars 1969B. Both probes were lost in launch-related complications with the newly developed Proton rocket.

1970s
The USSR intended to have the first artificial satellite of Mars beating the planned American Mariner 8 and Mariner 9 Martian orbiters. In May 1971, one day after Mariner 8 malfunctioned at launch and failed to reach orbit, Cosmos 419 (Mars 1971C), a heavy probe of the Soviet Mars program M-71, also failed to launch. This spacecraft was designed as an orbiter only, while the next two probes of project M-71, Mars 2 and Mars 3, were multipurpose combinations of an orbiter and a lander with small skis-walking rovers that would be the first planet rovers outside the Moon. They were successfully launched in mid-May 1971 and reached Mars about seven months later. On November 27, 1971 the lander of Mars 2 crash-landed due to an on-board computer malfunction and became the first man-made object to reach the surface of Mars. On 2 December 1971, the Mars 3 lander became the first spacecraft to achieve a soft landing, but its transmission was interrupted after 14.5 seconds.

The Mars 2 and 3 orbiters sent back a relatively large volume of data covering the period from December 1971 to March 1972, although transmissions continued through to August. By 22 August 1972, after sending back data and a total of 60 pictures, Mars 2 and 3 concluded their missions. The images and data enabled creation of surface relief maps, and gave information on the Martian gravity and magnetic fields.

In 1973, the Soviet Union sent four more probes to Mars: the Mars 4 and Mars 5 orbiters and the Mars 6 and Mars 7 fly-by/lander combinations. All missions except Mars 7 sent back data, with Mars 5 being most successful. Mars 5 transmitted 60 images before a loss of pressurization in the transmitter housing ended the mission. Mars 6 lander transmitted data during descent, but failed upon impact. Mars 4 flew by the planet at a range of 2200 km returning one swath of pictures and radio occultation data, which constituted the first detection of the nightside ionosphere on Mars. Mars 7 probe separated prematurely from the carrying vehicle due to a problem in the operation of one of the onboard systems (attitude control or retro-rockets) and missed the planet by 1300 km.

Mariner program


In 1964, NASA's Jet Propulsion Laboratory made two attempts at reaching Mars. Mariner 3 and Mariner 4 were identical spacecraft designed to carry out the first flybys of Mars. Mariner 3 was launched on November 5, 1964, but the shroud encasing the spacecraft atop its rocket failed to open properly, dooming the mission. Three weeks later, on November 28, 1964, Mariner 4 was launched successfully on a 7½-month voyage to Mars..

Mariner 4 flew past Mars on July 14, 1965, providing the first close-up photographs of another planet. The pictures, gradually played back to Earth from a small tape recorder on the probe, showed impact craters. It provided radically more accurate data about the planet; a surface atmospheric pressure of about 1% of Earth's and daytime temperatures of −100 °C (−148 °F) were estimated. No magnetic field or Martian radiation belts were detected. The new data meant redesigns for then planned Martian landers, and showed life would have a more difficult time surviving there than previously anticipated.

NASA continued the Mariner program with another pair of Mars flyby probes, Mariner 6 and 7. They were sent at the next launch window, and reached the planet in 1969. During the following launch window the Mariner program again suffered the loss of one of a pair of probes. Mariner 9 successfully entered orbit about Mars, the first spacecraft ever to do so, after the launch time failure of its sister ship, Mariner 8. When Mariner 9 reached Mars in 1971, it and two Soviet orbiters (Mars 2 and Mars 3, see Mars probe program below) found that a planet-wide dust storm was in progress. The mission controllers used the time spent waiting for the storm to clear to have the probe rendezvous with, and photograph, Phobos. When the storm cleared sufficiently for Mars' surface to be photographed by Mariner 9, the pictures returned represented a substantial advance over previous missions. These pictures were the first to offer more detailed evidence that liquid water might at one time have flowed on the planetary surface. They also finally discerned the true nature of many Martian albedo features. For example, Nix Olympica was one of only a few features that could be seen during the planetary duststorm, revealing it to be the highest mountain (volcano, to be exact) on any planet in the entire Solar System, and leading to its reclassification as Olympus Mons.

Viking program
The Viking program launched Viking 1 and 2 spacecraft to Mars in 1975; The program consisted of two orbiters and two landers – these were the first two spacecraft to successfully land and operate on Mars.

The primary scientific objectives of the lander mission were to search for biosignatures and observe meteorologic, seismic and magnetic properties of Mars. The results of the biological experiments on board the Viking landers remain inconclusive, with a reanalysis of the Viking data published in 2012 suggesting signs of microbial life on Mars.

The Viking orbiters revealed that large floods of water carved deep valleys, eroded grooves into bedrock, and traveled thousands of kilometers. Areas of branched streams, in the southern hemisphere, suggest that rain once fell.

Mars Pathfinder


Mars Pathfinder was a U.S. spacecraft that landed a base station with a roving probe on Mars on July 4, 1997. It consisted of a lander and a small 10.6 kg wheeled robotic rover named Sojourner, which was the first rover to operate on the surface of Mars. In addition to scientific objectives, the Mars Pathfinder mission was also a "proof-of-concept" for various technologies, such as an airbag landing system and automated obstacle avoidance, both later exploited by the Mars Exploration Rovers.

Mars Global Surveyor
After the 1992 failure of NASA's Mars Observer orbiter, NASA retooled and launched Mars Global Surveyor (MGS). This mission was the first successful United States mission, and the first fully successful mission overall, to the red planet in two decades when it launched November 7, 1996, and entered orbit on September 12, 1997. After a year and a half trimming its orbit from a looping ellipse to a circular track around the planet, the spacecraft began its primary mapping mission in March 1999. It observed the planet from a low-altitude, nearly polar orbit over the course of one complete Martian year, the equivalent of nearly two Earth years. Mars Global Surveyor completed its primary mission on January 31, 2001, and completed several extended mission phases.

The mission studied the entire Martian surface, atmosphere, and interior, and returned more data about the red planet than all previous Mars missions combined. The data has been archived and remains available publicly.

Among key scientific findings, Global Surveyor took pictures of gullies and debris flow features that suggest there may be current sources of liquid water, similar to an aquifer, at or near the surface of the planet. 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.

Magnetometer readings showed that the planet's magnetic field is not globally generated in the planet's core, but is localized in particular areas of the crust. New temperature data and closeup images of the Martian moon Phobos showed that its surface is composed of powdery material at least 1 metre (3 feet) thick, caused by millions of years of meteoroid impacts. Data from the spacecraft's laser altimeter gave scientists their first 3-D views of Mars' north polar ice cap. On November 5, 2006 MGS lost contact with Earth. NASA ended efforts to restore communication on January 28, 2007.

Mars Odyssey and Mars Express
In 2001, NASA's Mars Odyssey orbiter arrived at Mars. Its mission is to use spectrometers and imagers to hunt for evidence of past or present water and volcanic activity on Mars. In 2002, it was announced that the probe's gamma ray spectrometer and neutron spectrometer had detected large amounts of hydrogen, indicating that there are vast deposits of water ice in the upper three meters of Mars' soil within 60° latitude of the south pole.

On June 2, 2003, the European Space Agency's Mars Express set off from Baikonur Cosmodrome to Mars. The Mars Express craft consists of the Mars Express Orbiter and the stationary lander Beagle 2. The lander carried a digging device and the smallest mass spectrometer created to date, as well as a range of other devices, on a robotic arm in order to accurately analyze soil beneath the dusty surface to look for biosignatures and biomolecules.

The orbiter entered Mars orbit on December 25, 2003, and Beagle 2 entered Mars' atmosphere the same day. However, attempts to contact the lander failed. Communications attempts continued throughout January, but Beagle 2 was declared lost in mid-February, and a joint inquiry was launched by the UK and ESA. The Mars Express Orbiter confirmed the presence of water ice and carbon dioxide ice at the planet's south pole, while NASA had previously confirmed their presence at the north pole of Mars.

The lander's fate remained a mystery until it was located intact on the surface of Mars in a series of images from the Mars Reconnaissance Orbiter. The images suggest that two of the spacecraft's four solar panels failed to deploy, blocking the spacecraft's communications antenna. Beagle 2 is the first British and first European probe to achieve a soft landing on Mars.

MER and Phoenix
NASA's Mars Exploration Rover Mission (MER), started in 2003, is an ongoing robotic space mission involving two rovers, Spirit (MER-A) and Opportunity, (MER-B) exploring the Martian surface geology. The mission's scientific objective is to search for and characterize a wide range of rocks and soils that hold clues to past water activity on Mars. The mission is part of NASA's Mars Exploration Program, which includes three previous successful landers: the two Viking program landers in 1976; and Mars Pathfinder probe in 1997.

Mars Reconnaissance Orbiter
Mars Reconnaissance Orbiter is a multipurpose spacecraft designed to conduct reconnaissance and exploration of Mars from orbit. The $720 million USD spacecraft was built by Lockheed Martin under the supervision of the Jet Propulsion Laboratory, launched August 12, 2005, and attained Martian orbit on March 10, 2006.

The MRO contains a host of scientific instruments such as the HiRISE camera, CTX camera, CRISM, and SHARAD. The HiRISE camera is used to analyze Martian landforms, whereas CRISM and SHARAD can detect water, ice, and minerals on and below the surface. Additionally, MRO is paving the way for upcoming generations of spacecraft through daily monitoring of Martian weather and surface conditions, searching for future landing sites, and testing a new telecommunications system that enable it to send and receive information at an unprecedented bitrate, compared to previous Mars spacecraft. Data transfer to and from the spacecraft occurs faster than all previous interplanetary missions combined and allows it to serve as an important relay satellite for other missions.

Rosetta and Dawn swingbys
The ESA Rosetta space probe mission to the comet 67P/Churyumov-Gerasimenko flew within 250 km of Mars on February 25, 2007, in a gravitational slingshot designed to slow and redirect the spacecraft.

The NASA Dawn spacecraft used the gravity of Mars in 2009 to change direction and velocity on its way to Vesta, and tested out Dawn cameras and other instruments on Mars.

Fobos-Grunt
In November 8, 2011, Russia's Roscosmos launched an ambitious mission called Fobos-Grunt. It consisted of a lander aimed to retrieve a sample back to Earth from Mars' moon Phobos, and place the Chinese Yinghuo-1 probe in Mars' orbit. The Fobos-Grunt mission suffered a complete control and communications failure shortly after launch and was left stranded in low Earth orbit, later falling back to Earth. The Yinghuo-1 satellite and Fobos-Grunt underwent destructive re-entry on January 15, 2012, finally disintegrating over the Pacific Ocean.

Curiosity rover
The NASA Mars Science Laboratory mission with its rover named Curiosity, was launched on November 26, 2011, and landed on Mars on August 6, 2012 on Aeolis Palus in Gale Crater. The rover carries instruments designed to look for past or present conditions relevant to the past or present habitability of Mars.

MAVEN
NASA's MAVEN is an orbiter mission to study the upper atmosphere of Mars. It will also serve as a communications relay satellite for robotic landers and rovers on the surface of Mars. MAVEN was launched 18 November 2013 and reached Mars on 22 September 2014.

Mars Orbiter Mission
The Mars Orbiter Mission, also called Mangalyaan, was launched on 5 November 2013 by the Indian Space Research Organisation (ISRO). It was successfully inserted into Martian orbit on 24 September 2014. The mission is a technology demonstrator, and as secondary objective, it will also study the Martian atmosphere. This is India's first mission to Mars, and with it, ISRO became the fourth space agency to successfully reach Mars after the Soviet Union, NASA (USA) and ESA (Europe). It also made ISRO the second space agency to reach Mars orbit on its first attempt (the first national one, after the international ESA), and also the first Asian country to successfully send an orbiter to Mars. It was completed in a record low budget of $71 million, making it the least-expensive Mars mission to date.

Future missions

 * In August 2012, NASA selected InSight, a $425 million lander mission for 2016, with a drill and seismometer to determine the interior structure of Mars. Two flyby CubeSats called MarCO will be launched with InSight to provide real-time telemetry during the entry and landing of InSight.  The CubeSats will separate from the Atlas V booster after launch and travel on their own trajectories to Mars.   The launch has been rescheduled from March 2016 to May 2018.
 * As part of the ExoMars program, ESA and the Russian Federal Space Agency plan to send the ExoMars rover in 2020 to search for past or present microscopic life on Mars.
 * The ISRO plans to send a follow up mission to its Mars Orbiter Mission in the 2018-2020 timeframe; it is called Mangalyaan 2. This mission will consist of a lander and a rover.
 * The Mars 2020 rover mission by NASA will be launched in 2020, and it is based on the Mars Science Laboratory design. The scientific payload will be focused on astrobiology.
 * The 2020 Chinese Mars Mission is planned to comprise an orbiter, a lander and a small rover.
 * The United Arab Emirates will send an orbiter to Mars, the Emirates Mars Mission, in 2020.

Proposals

 * The Finnish-Russian Mars MetNet concept would use multiple small meteorological stations on Mars to establish a widespread observation network to investigate the planet's atmospheric structure, physics and meteorology. The MetNet precursor or demonstrator was considered for a piggyback launch on Fobos-Grunt, and on the two proposed to fly on the 2016 and 2020 ExoMars spacecraft.
 * The Mars-Grunt is a Russian mission concept to bring a sample of Martian soil to Earth.
 * A ESA-NASA team produced a three-launch architecture concept for a Mars sample return, which uses a rover to cache small samples, a Mars ascent stage to send it into orbit, and an orbiter to rendezvous with it above Mars and take it to Earth. Solar-electric propulsion could allow a one launch sample return instead of three.
 * The Mars Scout Program's SCIM would involve a probe grazing the upper atmosphere of Mars to collect dust and air for return to Earth.
 * On 10 Nov 2014, China unveiled a prototype model of a Mars rover based on its lunar rover Yutu at an annual air show at Zhuhai. The CASC also said that a mission including an orbiter, lander and the rover (2020 Chinese Mars Mission) will be sent in 2020.
 * Japan is working on a mission concept called MELOS rover that would look for biosignatures of extant life on Mars.

Other future mission concepts include polar probes, Martian aircraft and a network of small meteorological stations. Longterm areas of study may include Martian lava tubes, resource utilization, and electronic charge carriers in rocks. Micromissions are another possibility, such as piggybacking a small spacecraft on an Ariane 5 rocket and using a lunar gravity assist to get to Mars.

Human mission proposals


Many people have long advocated a human mission to Mars, perhaps eventually leading to the permanent colonization of Mars, as the next logical step for a human space program after lunar exploration. Aside from the prestige such a mission would bring, advocates argue that humans would easily be able to outperform robotic explorers, justifying the expense. Aerospace engineer Bob Zubrin is one of the proponents of such missions. Some critics contend unmanned robots can perform better than humans at a fraction of the expense. If life exists on Mars, a human mission could contaminate it by introducing earthly microbes, so robotic exploration would be preferable.

ESA
The ESA has plans to land humans on Mars between 2030 and 2035. This will be preceded by successively larger probes, starting with the launch of the ExoMars probe and a planned joint NASA–ESA Mars sample return mission.

NASA
Human exploration by the United States was identified as a long-term goal in the Vision for Space Exploration announced in 2004 by then US President George W. Bush. The planned Orion spacecraft would be used to send a human expedition to Earth's moon by 2020 as a stepping stone to a Mars expedition. On September 28, 2007, NASA administrator Michael D. Griffin stated that NASA aims to put a person on Mars by 2037.

On December 2, 2014, NASA's Advanced Human Exploration Systems and Operations Mission Director Jason Crusan and Deputy Associate Administrator for Programs James Reuthner announced tentative support for the Boeing "Affordable Mars Mission Design" including radiation shielding, centrifugal artificial gravity, in-transit consumable resupply, and a lander which can return. Reuthner suggested that if adequate funding was forthcoming, the proposed mission would be expected in the early 2030s.

On October 8, 2015, NASA published its official plan for human exploration and colonization of Mars. The plan operates through three distinct phases leading up to fully sustained colonization. The first stage, already underway, is the "Earth Reliant" phase. This phase continues utilizing the International Space Station until 2024; validating deep space technologies and studying the effects of long duration space missions on the human body. The second stage, "Proving Ground," moves away from Earth reliance and ventures into cislunar space for most of its tasks. This is when NASA plans to capture an asteroid (planned for 2020), test deep space habitation facilities, and validate capabilities required for human exploration of Mars. Finally, phase three is the transition to independence from Earth resources. The "Earth Independent" phase includes long term missions on the lunar surface which leverage surface habitats that only require routine maintenance, and the harvesting of Martian resources for fuel, water, and building materials. NASA is still aiming for human missions to Mars in the 2030s, though Earth independence could take decades longer.

Zubrin
Mars Direct, a low-cost human mission proposed by Robert Zubrin, founder of the Mars Society, would use heavy-lift Saturn V class rockets, such as the Ares V, to skip orbital construction, LEO rendezvous, and lunar fuel depots. A modified proposal, called "Mars to Stay", involves not returning the first immigrant explorers immediately, if ever (see Colonization of Mars).

Probing difficulties


The challenge, complexity and length of Mars missions have led to many mission failures. The high failure rate of missions launched from Earth attempting to explore Mars is informally called the "Mars Curse" or "Martian Curse". The phrase "Galactic Ghoul" or "Great Galactic Ghoul", referring to a fictitious space monster that subsists on a diet of Mars probes, was coined in 1997 by Time Magazine journalist Donald Neff, and is sometimes facetiously used to "explain" the recurring difficulties.

Two Soviet probes were sent to Mars in 1988 as part of the Phobos program. Phobos 1 operated normally until an expected communications session on 2 September 1988 failed to occur. The problem was traced to a software error, which deactivated attitude thrusters causing the spacecrafts' solar arrays to no longer point at the Sun, depleting Phobos 1 batteries. Phobos 2 operated normally throughout its cruise and Mars orbital insertion phases on January 29, 1989, gathering data on the Sun, interplanetary medium, Mars, and Phobos. Shortly before the final phase of the mission, during which the spacecraft was to approach within 50 m of Phobos' surface and release two landers, one a mobile 'hopper', the other a stationary platform, contact with Phobos 2 was lost. The mission ended when the spacecraft signal failed to be successfully reacquired on March 27, 1989. The cause of the failure was determined to be a malfunction of the on-board computer.

Just a few years later in 1992 Mars Observer, launched by NASA, failed as it approached Mars. Mars 96, an orbiter launched on November 16, 1996 by Russia failed, when the planned second burn of the Block D-2 fourth stage did not occur.

Following the success of Global Surveyor and Pathfinder, another spate of failures occurred in 1998 and 1999, with the Japanese Nozomi orbiter and NASA's Mars Climate Orbiter, Mars Polar Lander, and Deep Space 2 penetrators all suffering various fatal errors. Mars Climate Orbiter was noted for mixing up U.S. customary units with metric units, causing the orbiter to burn up while entering Mars' atmosphere.

Timeline of Mars exploration
Source:

Undeveloped concepts

 * Mars 4NM and Mars 5NM – projects intended by the Soviet Union for heavy Marsokhod (in 1973 according to initial plan of 1970) and Mars sample return (planned for 1975) missions by launching on N1 (rocket) that has never flown successfully.
 * Mars 5M (Mars-79) – double-launching Soviet sample return mission planned to 1979 but cancelled due to complexity and technical problems
 * Vesta - the multiaimed Soviet mission, developed in cooperation with European countries for realisation in 1991–1994 but canceled due to the Soviet Union disbanding, included the flyby of Mars with delivering the aerostat and small landers or penetrators followed by flybys of 1 Ceres or 4 Vesta and some other asteroids with impact of penetrator on the one of them.
 * Voyager-Mars – USA, 1970s – Two orbiters and two landers, launched by a single Saturn V rocket.
 * Mars Aerostat – Russian/French balloon part for cancelled Vesta mission and then for failed Mars 96 mission, originally planned for the 1992 launch window, postponed to 1994 and then to 1996 before being cancelled.
 * Mars Environmental Survey – set of 16 landers planned for 1999–2009
 * Mars-98 – Russian mission including an orbiter, lander, and rover, planned for 1998 launch opportunity as repeat of failured Mars 96 mission and cancelled due to lack of funding
 * Mars Surveyor 2001 Lander – October 2001 – Mars lander (refurbished, became Phoenix lander)
 * Beagle 3 – 2009 British lander mission meant to search for life, past or present.
 * ''NetLander – 2007 or 2009 – Mars netlanders
 * Mars Telecommunications Orbiter – September 2009 – Mars orbiter for telecommunications
 * Sky-Sailor – 2014 – Plane developed by Switzerland to take detailed pictures of Mars surface
 * Mars Astrobiology Explorer-Cacher – 2018 rover
 * Kitty Hawk – Mars airplane micromission, proposed for December 17, 2003, the centennial of the Wright brothers' first flight. Its funding was eventually given to the 2003 Mars Network project.
 * Tumbleweed rover.