Lander (spacecraft)
A lander is a spacecraft that descends towards, then comes to rest on the surface of an astronomical body other than Earth. In contrast to an impact probe, which makes a hard landing that damages or destroys the probe upon reaching the surface, a lander makes a soft landing after which the probe remains functional.
For bodies with atmospheres, the landing occurs after atmospheric entry. In these cases, landers may employ parachutes to slow them down enough to maintain a low terminal velocity. In some cases, small landing rockets will be fired just before impact in order to reduce the lander's velocity. Landing may be accomplished by controlled descent and set down on landing gear, with the possible addition of a post-landing attachment mechanism for celestial bodies with low gravity. Some missions used inflatable airbags to cushion the lander's impact rather than utilizing more traditional landing gear.
When a high-velocity impact is intentionally planned in order to study the consequences of impact, the spacecraft is called an impactor.
Several terrestrial bodies have been subject to lander or impactor exploration. Among them are Earth's Moon; the planets Venus, Mars, and Mercury; Saturn's moon Titan; asteroids; and comets.
Landers
Lunar
Beginning with Luna 2 in 1959, the first few spacecraft to reach the lunar surface were impactors, not landers. They were part of the Soviet Luna program or the American Ranger program.In 1966, the Soviet Luna 9 became the first spacecraft to achieve a lunar soft landing and to transmit photographic data to Earth. The American Surveyor program was designed to determine where Apollo could land safely. As a result, these robotic missions required soft landers to sample the lunar soil and determine the thickness of the dust layer, which was unknown before Surveyor.
The U.S.-crewed Apollo Lunar Modules with rovers and late Soviet large robotic landers, Lunokhods and sample return missions used a rocket descent engine for a soft landing of astronauts and lunar rovers on the Moon.
The Chinese Chang'e 3 mission and its Yutu rover landed on 14 December 2013. In 2019, China's Chang'e 4 mission successfully landed the Yutu-2 rover on the far side of the Moon. Chang'e 5 and Chang'e 6 are designed to be sample return missions. Chang'e 5 and 6 were conducted successfully in 2020 and 2024 respectively. Chang'e 5 mission landed on the Moon on 1 December 2020, China completed the Chang'e 5 mission on 16 December 2020 with the return of approximately 2 kilograms of lunar sample.
On 6 September 2019, the lander Vikram on Chandrayaan-2, attempting to land on the lunar south polarregion. Due to software glitch, it lost contact and crashed moments before landing.
About 4 years later, on 23 August 2023, the lander Vikram on Chandrayaan-3 successfully touched down on the lunar south pole, close to the crater Manzinus U. This made it the first lander to soft land at the south pole of the Moon.
Japan became the fifth country to land a lunar probe on 19 January 2024, by successfully landing its SLIM lander.
On 22 February 2024, Intuitive Machine's Odysseus successfully landed on the Moon after taking off on a SpaceX Falcon 9. This was the first successful landing of a privately owned spacecraft on the Moon.
China sent Chang'e 6 on 3 May 2024, which conducted the first lunar sample return from Apollo Basin on the far side of the Moon. This is China's second lunar sample return mission, the first was achieved by Chang'e 5 from the lunar near side four years earlier. It also carried the Chinese Jinchan rover to conduct infrared spectroscopy of lunar surface and imaged Chang'e 6 lander on lunar surface. The lander-ascender-rover combination was separated with the orbiter and returner before landing on 1 June 2024 at 22:23 UTC. It landed on the Moon's surface on 1 June 2024. The ascender was launched back to lunar orbit on 3 June 2024 at 23:38 UTC, carrying samples collected by the lander, and later completed another robotic rendezvous and docking in lunar orbit. The sample container was then transferred to the returner, which landed in Inner Mongolia on 25 June 2024, completing China's far side extraterrestrial sample return mission.
Venus
The Soviet Venera program included a number of Venus landers, some of which were crushed during descent much as Galileo's Jupiter "lander" and others which successfully touched down. Venera 3 in 1966 and Venera 7 in 1970 became the first impact and soft landing on Venus respectively. The Soviet Vega program also placed two balloons in the Venusian atmosphere in 1985, which were the first aerial tools on other planets.Mars
The Soviet Union's Mars 1962B became the first mission intended to impact on Mars in 1962. In 1971, the lander of the Mars 3 probe conducted the first soft landing on Mars, but communication was lost within a minute after touchdown, which occurred during one of the worst global dust storms since the beginning of telescopic observations of the Red Planet. Three other landers, Mars 2 in 1971 and Mars 5 and Mars 6 in 1973, either crashed or failed to even enter the planet's atmosphere. All four landers used an aeroshell-like heat shield during atmospheric entry. Mars 2 and Mars 3 landers carried the first small skis-walking Mars rovers, PrOP-M, that did not work on the planet.The Soviet Union planned the heavy Marsokhod Mars 4NM mission in 1973 and the Mars sample return Mars 5NM mission in 1975, but neither occurred due to needing the N1 super-launcher that was never flown successfully. A double-launching Soviet Mars 5M sample return mission was planned for 1979 but cancelled due to complexity and technical problems.
NASA's Viking 1 and Viking 2 were launched respectively in August and September 1975, each comprising an orbiter vehicle and a lander. Viking 1 landed in July 1976 Viking 2 in September 1976. The Viking program rovers were the first successful, functioning Mars landers. The mission ended in May 1983, after both landers had stopped working.
Mars 96 was the first complex post-Soviet Russian mission with an orbiter, lander, penetrators. Planned for 1996, it failed at launch. A planned repeat of this mission, Mars 98, was cancelled due to lack of funding.
The U.S. Mars Pathfinder was launched in December 1996 and released the first acting rover on Mars, Sojourner, in July 1997. It worked until September 1997.
The Mars Polar Lander ceased communication on 3 December 1999 prior to reaching the surface and is presumed to have crashed.
The European Beagle 2 lander deployed successfully from the Mars Express spacecraft but the signal confirming a landing which should have come on 25 December 2003 was not received. No communication was ever established and Beagle 2 was declared lost on 6 February 2004. The proposed 2009 British Beagle 3 lander mission to search for life, past or present, was not adopted.
The American Mars Exploration Rovers Spirit and Opportunity were launched in June and July 2003. They reached the Martian surface in January 2004 using landers featuring airbags and parachutes to soften impact. Spirit ceased functioning in 2010, more than five years past its design lifetime. As of 13 February 2019, Opportunity was declared effectively dead, having exceeded its three-month design lifetime by well over a decade.
The U.S. spacecraft Phoenix successfully achieved soft landing on the surface of Mars on 25 May 2008, using a combination of parachutes and rocket descent engines.
Mars Science Laboratory, which carried the rover Curiosity, was launched by NASA on 26 November 2011. It landed in the Aeolis Palus region of Gale Crater on Mars on 6 August 2012.
China launched the Tianwen-1 mission, on 23 July 2020. It includes an orbiter, a lander and a 240 kilograms rover. The orbiter was placed into orbit on 10 February 2021. The Zhurong successfully soft landed on 14 May 2021 and deployed on 22 May 2021.
Martian moons
While several flybys conducted by Mars orbiting probes have provided images and other data about the Martian moons Phobos and Deimos, only few of them intended to land on the surface of these satellites. Two probes under the Soviet Phobos program were successfully launched in 1988, but in 1989 the intended landings on Phobos and Deimos were not conducted due to failures in the spacecraft system. The post-Soviet Russian Fobos-Grunt probe was an intended sample return mission to Phobos in 2012 but failed after launch in 2011.In 2007 European Space Agency and EADS Astrium proposed and developed the mission to Phobos to 2016 with lander and sample return, but it stayed as a project. Since 2007 the Canadian Space Agency has considered a mission to Phobos called Phobos Reconnaissance and International Mars Exploration, which would include an orbiter and lander. Recent proposals include a 2008 NASA Glenn Research Center Phobos and Deimos sample return mission, the 2013 Phobos Surveyor, and the OSIRIS-REx II mission concept.
The Japanese Aerospace Exploration Agency plans to launch the Martian Moons Exploration mission in 2026, a sample return mission targeting Phobos. MMX will land and collect samples from Phobos multiple times, along with deploying a rover jointly developed by CNES and the German Aerospace Center. By using a corer sampling mechanism, the spacecraft aims to retrieve a minimum of 10g of samples. MMX will return to Earth in 2029.
Titan (moon of Saturn)
The Huygens probe, carried to Saturn's moon Titan by Cassini, was specifically designed to survive landing on land or on liquid. It was thoroughly drop-tested to make sure it could withstand impact and continue functioning for at least three minutes. However, due to the low-speed impact, it continued providing data for more than two hours after it landed. The landing on Titan in 2005 was the first, and to date only, landing on any planet's satellite other than Earth's moon.The proposed U.S. Titan Mare Explorer mission considered a lander that would splash down in a lake in Titan's northern hemisphere and float on the surface of the lake for few months. Spain's proposed Titan Lake In-situ Sampling Propelled Explorer mission is similar to the TiME lander but has its own propulsion system for controlling shipping.