A Mars landing is a landing of a spacecraft on the surface of Mars. Of multiple attempted Mars landings by robotic, uncrewed spacecraft, ten have had successful soft landings. There have also been studies for a possible human mission to Mars including a landing, but none has been attempted. As of 2023, the Soviet Union, United States, and China have conducted Mars landings successfully. Soviet Mars 3, which landed in 1971, was the first successful Mars landing, though the spacecraft failed after 110 seconds on the surface. All other Soviet Mars landing attempts failed. Viking 1 and Viking 2 were first successful NASA landers, launched in 1975. NASA's Mars Pathfinder, launched in 1996, successfully delivered the first Mars rover, Sojourner. In 2021, first Chinese lander and rover, Tianwen 1, successfully landed on Mars. The British Beagle 2 landed in 2003, but because of loss of contact and mission failure its landing would only be confirmed in 2015.
Methods of descent and landing As of 2021, all methods of landing on Mars have used an aeroshell and parachute sequence for Mars atmospheric entry and descent, but after the parachute is detached, there are three options. 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 for lighter rovers is to enclose the rover in a tetrahedral 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 tether so that the airbags can inflate. Retrorockets on the back shell can slow descent. 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 tether. When the rover touches ground, it cuts the tether so that the sky crane (with its rockets still firing) will crash well away from the rover. Both Curiosity and Perseverance used sky crane for landing.
Descent of heavier payloads
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 (26 feet) in diameter. It would have to be accompanied by a proportionately larger parachute.
Landing challenges Landing robotic spacecraft, and possibly some day humans, on Mars is a technological challenge. For a favorable landing, the lander module has to address these issues:
Thinness of Mars's atmosphere Measurement of distance to surface Inadequate technology for ballistic aerocapture Inadequate technology for retropropulsive powered descent Inadequate mission designs Shorter time to perform entry, descent and landing (EDL) In 2018, NASA successfully landed the InSight lander on the surface of Mars, re-using Viking-era technology. But this technology cannot afford the ability to land large number of cargoes, habitats, ascent vehicles and humans in case of crewed Mars missions in near future. In order to improve and accomplish this intent, there is need to upgrade technologies and launch vehicles. Some of the criteria for a lander performing a successful soft-landing using current technology are as follows:
Communicating with Earth Beginning with the Viking program, all landers on the surface of Mars have used orbiting spacecraft as communications satellites for relaying their data to Earth. The landers use UHF transmitters to send their data to the orbiters, which then relay the data to Earth using either X band or Ka band frequencies. These higher frequencies, along with more powerful transmitters and larger parabolic reflectors, permit the orbiters to send the data much faster than the landers could manage transmitting directly to Earth, which conserves valuable time on the receiving antennas.
List of Mars landings
In the 1970s, several USSR probes unsuccessfully tried to land on Mars. Mars 3 landed successfully in 1971 but failed soon afterwards. But the American Viking landers made it to the surface and provided several years of images and data. However, the next successful Mars landing was not until 1997, when Mars Pathfinder landed. In the 21st century there have been several successful landings, but there have also been many crashes.
Mars probe program The first probe intended to be a Mars impact lander was the Soviet Mars 1962B, unsuccessfully launched in 1962. In 1970 the Soviet Union began the design of Mars 4NM and Mars 5NM missions with super-heavy uncrewed Martian spacecraft. First was Marsokhod, with a planned date of early 1973, and second was the Mars sample return mission planned for 1975. Both spacecraft were intended to be launched on the N1 rocket, but this rocket never flew successfully and the Mars 4NM and Mars 5NM projects were cancelled. In 1971 the Soviet Union sent probes Mars 2 and Mars 3, each carrying a lander, as part of the Mars probe program M-71. The Mars 2 lander failed to land and impacted Mars. The Mars 3 lander became the first probe to successfully soft-land on Mars, but its data-gathering had less success. The lander began transmitting to the Mars 3 orbiter 90 seconds after landing, but after 14.5 seconds, transmission ceased for unknown reasons. The cause of the failure may have been related to the extremely powerful Martian dust storm taking place at the time. These space probes each contained a Mars rover, PrOP-M, although they were never deployed. In 1973, the Soviet Union sent two more landers to Mars, Mars 6 and Mars 7. The Mars 6 lander transmitted data during descent but failed upon impact. The 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 1,300 km (810 mi). The double-launching Mars 5M (Mars-79) sample return mission was planned for 1979, but was cancelled due to complexity and technical problems.
Viking program
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