Mars landing

"For broader coverage of this topic, see Exploration of Mars."



A Mars landing is a landing of 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 have been attempted. Soviet Union's Mars 3, which landed in 1971, was the first successful Mars landing. As of May 2021, the Soviet Union, United States and China have conducted Mars landing successfully.

Methods of descent and landing
As of 2021, all methods of landing on Mars have used on 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 open 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 thether so that the sky crane (with its rockets still firing) will crash well away from the rover.

Descent of heavier paylods
For landers that are even heavier then the Curiosity rover (which required a 4.5 meters (15 feet) diameter airshell), engineers are developing a combination rigid-inflatable Low-Destiny Supersonic Decelerator that could be 8 meters (28 feet) in a 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. For a successive soft-landing using current technology, some of the considerable factors such as:


 * Mass should be less than 0.6 tonnes (1,300 lb)
 * Ballistic coefficient should be less than 35 kg/m2 (.2 lb/sq ft)
 * Diameter of the aeroshell should be less than 4.6 m (15 ft)
 * Geometry of the aeroshell should be 70° spherical cone shell
 * Diameter of the parachute should be less than 30 m (98 ft)
 * Need to use supersonic retropropulsive powered descent
 * Need to perform orbital entry (i.e., entry from Mars orbit)

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 antennas, 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. .