Mars landing



A Mars landing is a landing of a spacecraft on the surface of Mars. Of multiple attempted Mars landings by robotic, unmanned spacecraft, seven were successful. There have also been studies for a possible human mission to Mars, including a landing, but none have been attempted.

Methods of landing
All methods of landing on Mars require an aeroshell and parachute sequence, but after that there are three choices. A stationary lander can drop from the parachute back shell and ride retrorockets all the way down, but a rover cannot be burdened with rockets that serve no purpose after touchdown. One method is to enclose the rover in a tetrahedronal structure which in turn is enclosed in airbags. After the aeroshell drops off, the tetrahedron is lowered clear of the parachute back shell on a lanyard so that the airbags can inflate. When it nears the ground, the tetrahedron is released to drop to the ground, using the airbags as shock absorbers. When it has come to rest, the tetrahedron opens to expose the rover. If a rover is too heavy to use airbags, the retrorockets can be mounted on a sky crane. The sky crane drops from the parachute back shell and, as it nears the ground, the rover is lowered on a lanyard. When the rover touches ground, it cuts the lanyard so that the sky crane (with its rockets still firing) will crash well away from the rover. All three methods have advantages and disadvantages, requiring careful consideration by the engineers.

For landers that are even heavier than the Curiosity rover (which required a 4.5 meter (15 feet) diameter aeroshell), engineers are developing a combination rigid-inflatable Low-Density Supersonic Decelerator that could be 8 meters (28 feet) in diameter. It would have to be accompanied by a proportionately larger parachute.

Mars probe program
The first probe intended to be a Mars impact lander was the Soviet Mars 1962B unsuccessfully launched in 1962.

In 1971 the Soviet Union successfully sent probes Mars 2 and Mars 3, as part of the Mars probe program M-71. The Mars 2 and 3 probes each carried a lander, both of which failed upon landing. They were the first human artifacts to touch down on Mars. Mars 2 lander impacted on Mars only, while Mars 3 was the first Martian soft lander and was able to transmit from the Martian surface during the first 20 seconds, the first data and a portion of the first picture. These spaceprobes also contained the first mini-Mars rovers, although they were broken on landing.

The Mars 2 and 3 orbiters sent back a 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 magnetosphere.

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.

Years earlier, in 1970 Soviet Union began the design of Mars 4NM and Mars 5NM missions with superheavy unmanned Martian spacecraft. First was Marsokhod with planned date of start in 1973 and second was Mars sample return mission planned to 1975. Both spacecraft intended to launch on N1 superrocket. But this rocket never flew successfully and Mars 4NM and Mars 5NM projects were cancelled.

Later, double-launching Mars 5M (Mars-79) sample return mission was planned for 1979, but cancelled due to complexity and technical problems.

Viking program


In 1976 the two American Viking probes entered orbit about Mars and each released a lander module that made the first fully successful soft landing on the planet's surface. The two missions returned the first color pictures and extensive scientific information. Measured temperatures at the landing sites ranged from 150 to 250 K, with a variation over a given day of 35 to 50 K. Seasonal dust storms, pressure changes, and movement of atmospheric gases between the polar caps were observed. A biology experiment produced possible evidence of life, but it was not corroborated by other on-board experiments.

While searching for a suitable landing spot for Viking 2's lander, the Viking 1 orbiter photographed the landform that constitutes the so-called "Face on Mars" on July 25, 1976.

The Viking program was a descendant of the cancelled Voyager program, whose name was later reused for a pair of outer solar system probes.

Mars Pathfinder


The Mars Pathfinder spacecraft, launched one month after Global Surveyor, landed on July 4, 1997. Its landing site was an ancient flood plain in Mars' northern hemisphere called Ares Vallis, which is among the rockiest parts of Mars. It carried a tiny remote-controlled rover called Sojourner, which was the first acting Mars rover that traveled a few meters around the landing site, exploring the conditions and sampling rocks around it. Newspapers around the world carried images of the lander dispatching the rover to explore the surface of Mars in a way never achieved before.

Until the final data transmission on September 27, 1997, Mars Pathfinder returned 16,500 images from the lander and 550 images from the rover, as well as more than 15 chemical analyses of rocks and soil and extensive data on winds and other weather factors. Findings from the investigations carried out by scientific instruments on both the lander and the rover suggest that Mars was at one time in its past warm and wet, with water existing in its liquid state and a thicker atmosphere. The mission website was the most heavily trafficked up to that time.

Spate of failures
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 terminal errors. Mars Climate Orbiter is infamous for Lockheed Martin engineers mixing up the usage of English units with metric units, causing the orbiter to burn up while entering Mars' atmosphere.

Beagle 2
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 lander Beagle 2. Although the landing probe was not designed to move, it 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 analyse soil beneath the dusty surface.

The orbiter entered Mars orbit on December 25, 2003, and Beagle 2 should have 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 that blamed Colin Pillinger's poor project management. Nevertheless, Mars Express Orbiter confirmed the presence of water ice and carbon dioxide ice at the planet's south pole. NASA had previously confirmed their presence at the north pole of Mars.

Signs of the Beagle 2 lander were found in 2013 by the HiRISE camera on NASA’s Mars Reconnaissance Orbiter and the Beagle 2's presence confirmed in January 2015, several months after Pillinger's death. The lander appears to have successfully landed but not deployed all of its power and communications panels.

Mars Exploration Rovers
Shortly after the launch of Mars Express, NASA sent a pair of twin rovers toward the planet as part of the Mars Exploration Rover. On 10 June 2003, NASA's MER-A (Spirit) Mars Exploration Rover was launched. It successfully landed in Gusev Crater (believed once to have been a crater lake) on 3 January 2004. It examined rock and soil for evidence of the area's history of water. On July 7, 2003, a second rover, MER-B (Opportunity) was launched. It landed on 24 January 2004 in Meridiani Planum (where there are large deposits of hematite, indicating the presence of past water) to carry out similar geological work.



Despite a temporary loss of communication with the Spirit Rover (caused by a file system anomaly ) delaying exploration for several days, both rovers eventually began exploring their landing sites. The rover Opportunity landed in a particularly interesting spot, a crater with bedrock outcroppings. In fast succession mission team members announced on 2 March that data returned from the rover showed that these rocks were once "drenched in water", and on 23 March that it was concluded that they were laid down underwater in a salty sea. This represented the first strong direct evidence for liquid water being on Mars at some time in the past.

Towards the end of July 2005, it was reported by the Sunday Times that the rovers may have carried the bacteria Bacillus safensis to Mars. According to one NASA microbiologist, this bacteria could survive both the trip and conditions on Mars. A book containing this claim, Out of Eden by Alan Burdick, is due to be published in the United Kingdom. Despite efforts to sterilise both landers, neither could be assured to be completely sterile.

Having only been designed for three-month missions, they both lasted much longer than planned, and Spirit lost contact with Earth in March 2010. Opportunity, however, continues to carry out surveys of the planet, and surpassed 25 miles on its odometer in August 2014. These rovers have discovered new things, including Heat Shield Rock, the first meteorite to be discovered on another planet.

Phoenix Lander
Phoenix launched on August 4, 2007, and touched down on the northern polar region of Mars on May 25, 2008. It is famous for having been successfully photographed while landing, since this was the first time one spacecraft captured the landing of another spacecraft onto a planetary body (the Moon not being a planet, but a satellite).

Phoenix was followed by the Mars Science Laboratory, a rover more capable than Spirit and Opportunity. Originally the Mars Science Laboratory was intended for a launch during 2009 however, it was launched on November 26, 2011.

Russia launched Fobos-Grunt, a sample return mission to Phobos, along with the joint Chinese Yinghuo-1 Mars orbiter in November 2011, which went into Earth orbit successfully, but failed to launch to Mars.

Mars Science Laboratory
The Mars Science Laboratory (MSL) (and Curiosity rover), launched in November 2011, landed on Aeolis Palus, between Peace Vallis and Aeolis Mons ("Mount Sharp"), in Gale Crater on Mars on August 6, 2012, 05:17 UTC. The landing site was in Quad 51 ("Yellowknife")   of Aeolis Palus near the base of Aeolis Mons. The landing site was less than 2.4 km from the center of the rover's planned target site after a 350000000 mi journey. NASA named the landing site "Bradbury Landing" on August 22, 2012.

Future missions
The ExoMars Trace Gas Orbiter and Schiaparelli lander are currently en route to Mars, and are scheduled for an October 2016 arrival. The InSight lander is planned for a 2018 launch to study the deep interior of Mars. The 2018 Red Dragon lander will test entry, descent, and powered landing of a 6500 kg mass. Additional future missions are the Mars 2020 rover, the 2020 Chinese Mars Mission, and the Mangalyaan 2 rover. The ESA ExoMars rover, also planned for launch in 2020, should obtain soil samples from up to 2 meters depth and make an extensive search for biosignatures and biomolecules.
 * 2018
 * 2020

There is a proposal for a Mars Sample Return Mission by ESA and NASA, but this has been delayed until at least 2024. This mission would be part of the European Aurora Programme.