Lander (spacecraft)

• 1. Introduction

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  A lander is a spacecraft built to do something extraordinarily difficult: descend toward an alien world and come to rest on its surface without being destroyed in the process. That single distinction separates landers from a different category of probe called an impactor, which hits a surface hard enough to wreck itself upon arrival. Landers survive. They touch down gently, and then they get to work.

  The challenge changes with every destination. Bodies with atmospheres allow a spacecraft to use air resistance and parachutes on the way down. Worlds with almost no gravity require harpoons or airbags. Some surfaces are scalding hot, some are bathed in corrosive chemistry, and at least one is covered in a liquid sea of methane. How do engineers solve each of these problems? And which worlds have humans actually managed to reach, softly, over the decades since the first attempts?

  The story of landers begins in 1959 and spans every corner of the inner solar system, from the far side of the Moon to the dust storms of Mars, from the crushing pressure of Venus to the nucleus of a comet. Each mission attempted something the one before it could not quite manage.

• 2. First Steps on the Moon

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  Luna 9, launched by the Soviet Union, became the first spacecraft to achieve a soft lunar landing in 1966, and it sent back photographic data to prove it. Before that moment, every probe that reached the Moon had been an impactor, crashing deliberately into the surface. Luna 9 changed the category.

  America answered with the Surveyor program, which ran from 1966 to 1968. These robotic landers had a specific job: determine where the Apollo astronauts could land safely. Before Surveyor, no one knew how thick the dust layer on the Moon actually was. The fear was real: a crewed lander might simply sink.

  The Apollo Lunar Modules flew between 1969 and 1972 and carried astronauts to the surface using rocket descent engines for a controlled soft landing. Later Soviet missions took a different approach entirely, sending large robotic landers called Lunokhods between 1970 and 1973 and running sample return missions through 1976.

  Decades passed before China entered the picture. Chang'e 3 and its Yutu rover landed on the 14th of December 2013. Six years later, Chang'e 4 landed the Yutu-2 rover on the far side of the Moon, a feat no mission had attempted before. Then came the sample return campaigns: Chang'e 5 touched down on the 1st of December 2020 and returned approximately 2 kilograms of lunar material by the 16th of December 2020.

  India's Chandrayaan-2 mission attempted a landing on the lunar south polar region on the 6th of September 2019, but a software glitch caused the Vikram lander to lose contact and crash moments before touchdown. Four years later, on the 23rd of August 2023, a redesigned Vikram lander on Chandrayaan-3 successfully touched down near the crater Manzinus U, becoming the first spacecraft to soft-land at the lunar south pole.

  Japan landed its SLIM probe on the 19th of January 2024, becoming the fifth country to achieve a lunar landing. Less than five weeks later, on the 22nd of February 2024, Intuitive Machines' Odysseus became the first privately owned spacecraft to successfully land on the Moon, arriving after launching on a SpaceX Falcon 9.

• 3. Mars: Fifty Years of Landings

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  Mars 3, a Soviet probe, became the first to achieve a soft landing on Mars in 1971. It managed to return data for less than a minute after touchdown, which happened during one of the worst global dust storms recorded since telescopic observations of the planet began. Three companion missions that year and in 1973 either crashed or failed to reach the atmosphere at all.

  NASA's Viking 1 and Viking 2 were launched in August and September 1975. Viking 1 landed in July 1976 and Viking 2 that September. These were the first Mars landers to function successfully for an extended period. The Viking program continued operating until May 1983.

  Mars Pathfinder, launched in December 1996, released the rover Sojourner in July 1997. Rather than retrorockets alone, Pathfinder used inflatable airbags to cushion the landing. Sojourner worked until September 1997. The Mars Polar Lander, by contrast, ceased communication on the 3rd of December 1999 before reaching the surface and is presumed to have crashed.

  The European Beagle 2 lander separated from Mars Express and was expected to signal a landing on the 25th of December 2003. No signal came. Beagle 2 was declared lost on the 6th of February 2004.

  Spirit and Opportunity, the Mars Exploration Rovers, launched in June and July 2003 and reached Mars in January 2004 using airbags and parachutes. Spirit was designed to last three months but kept working until 2010. Opportunity exceeded its three-month design lifetime by more than a decade; NASA declared it effectively dead on the 13th of February 2019.

  Mars Science Laboratory, carrying the rover Curiosity, launched on the 26th of November 2011 and landed in the Aeolis Palus region of Gale Crater on the 6th of August 2012. China's Tianwen-1, launched on the 23rd of July 2020, delivered the Zhurong rover, which soft-landed on the 14th of May 2021 and deployed on the 22nd of May 2021. Zhurong's mass was 240 kilograms.

• 4. Venus and Its Crushing Welcome

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  Venus punished the probes sent to land on it. The Soviet Venera program deployed a series of Venus landers, and some were crushed during descent before they ever reached the surface. The atmosphere of Venus is so thick and hot that surviving the trip down was an engineering achievement in itself.

  Venera 3 reached Venus in 1966 as an impact probe, the first spacecraft to reach the surface of another planet. Venera 7, in 1970, became the first to achieve a soft landing on Venus and return data from the surface. The Soviet Vega program later placed two balloons into the Venusian atmosphere in 1985, making them the first aerial tools ever deployed on another planet.

  The comparison with Mercury is telling. ESA's BepiColombo mission, launched in October 2018, was originally designed to include a Mercury Surface Element lander carrying a 7-kilogram payload. That payload would have included cameras, a heat flow package, an alpha particle X-ray spectrometer, a magnetometer, a seismometer, a soil penetrator, and a micro-rover. The lander portion was cancelled in 2003 due to budget constraints, but the orbiting components of BepiColombo are still expected to reach Mercury in November 2026.

• 5. Titan, Comets, and Unusual Surfaces

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  The Huygens probe faced a problem no previous lander engineer had solved: it might come to rest on solid ground or in a liquid lake. Engineers designed it to survive either. They drop-tested the probe thoroughly to confirm it could withstand impact and keep transmitting for at least three minutes. In 2005, when Huygens landed on Titan, Saturn's moon, the low-speed impact allowed it to keep sending data for more than two hours. That landing remains the only one ever made on any moon other than Earth's.

  Rosetta's Philae lander tackled a different extreme: the near-zero gravity of comet Churyumov-Gerasimenko. With so little gravity to hold it down, the landing system included a harpoon launcher designed to fire a cable into the comet's surface and pull the lander toward it. Philae was set down on the 12th of November 2014, becoming the first robotic lander on a comet. Rosetta itself had launched on the 2nd of March 2004, meaning the team waited more than a decade for that moment.

  Asteroids presented their own complications. NEAR Shoemaker landed on asteroid 433 Eros in 2001, despite not having been designed to land. The Japanese Hayabusa probe made several attempts to land on asteroid 25143 Itokawa in 2005, achieving mixed results and failing to deploy its rover. In 2010, Hayabusa became the first mission to return samples from an asteroid. JAXA's follow-up, Hayabusa2, launched in 2014 and delivered multiple landers to its target asteroid in 2018-2019, including the Minerva II landers and the German-built MASCOT lander, before returning samples to Earth.

• 6. Impactors: Science Through Collision

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  Not every probe that hits a surface has failed. Some are sent precisely to crash, because the collision itself is the experiment.

  NASA's Deep Impact probe visited comet Tempel 1 on the 4th of July 2005. The impact carved a crater approximately 200 meters wide and 30-50 meters deep. Scientists detected silicates, carbonates, smectite, amorphous carbon, and polycyclic aromatic hydrocarbons in the debris.

  India's Moon Impact Probe, developed by the Indian Space Research Organisation and released from the Chandrayaan-1 orbiter on the 14th of November 2008, was sent to strike the lunar surface. Chandrayaan-1 had launched on the 22nd of October 2008. The mission led to the detection of water on the Moon.

  NASA's LCROSS mission approached the same question from a different angle. Launched on the 18th of June 2009 alongside the Lunar Reconnaissance Orbiter, LCROSS directed a spent Centaur rocket stage to impact crater Cabeus near the lunar south pole at 11:31 UTC on the 9th of October 2009. A shepherding spacecraft then flew through the debris plume, collecting data before it too impacted six minutes later at 11:37 UTC. The project confirmed the presence of water ice in Cabeus.

  The MESSENGER spacecraft to Mercury took a different path to impact. After completing its mapping mission, it was directed to strike Mercury's surface on the 30th of April 2015, leaving an estimated crater 16 meters in diameter. ESA's DART mission impacted asteroid 65803 Didymos's moon Dimorphos in 2022, and the Hera spacecraft is planned to arrive in 2027 to assess what the collision actually did to the asteroid's orbit.

• 7. What Comes Next

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  JAXA's Martian Moons Exploration mission, known as MMX, is planned to launch in 2026 and return to Earth in 2029. It will land on Phobos multiple times, using a corer mechanism aimed at retrieving a minimum of 10 grams of material. It will also carry a rover developed jointly by CNES and the German Aerospace Center.

  NASA's Artemis IV mission, planned for 2028, would send the first crewed lunar landing in more than fifty years. The planned landing site is the lunar south pole, an area that only the Chandrayaan-3 mission has reached so far. The mission is designed to last approximately 30 days, oriented toward establishing a sustained human presence on the Moon rather than a brief visit.

  Europa remains a target without a confirmed lander. NASA's Europa Clipper is planned to begin exploring Jupiter's moons starting in 2030. A companion lander or impactor was considered but ultimately not approved. The scientific argument for landing on Europa rests on the hypothesis that liquid water exists beneath its icy surface, making it one of the most compelling places to search for life beyond Earth.