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A lander is a type of spacecraft which descends to come to rest on the surface of an astronomical body. For bodies with atmospheres, landers employ aerobraking and parachutes to slow down, often with small landing rockets which fire just before impact to bring the lander to rest relatively gently. The Mars Pathfinder mission also used inflateable airbags to cushion the lander's impact.

The Rosetta probe, which has not yet been launched at the time of writing, will put a lander on a still-to-be-determined comet; due to the extremely low gravity of such bodies, its landing system includes a harpoon launcher intended to anchor a cable in the surface and pull it down. A landing on a similarly small body, the asteroid 433 Eros, was performed by the satellite NEAR Shoemaker despite the fact that NEAR was not originally designed to be capable of landing.

The Galileo probe dropped a small reentry vehicle into the atmosphere of Jupiter, but as Jupiter is a gas giant with no well-defined surface it is debatable whether this was a "lander" per se.

A number of Moon probes, such as some members of the Soviet Luna program and the American Ranger program, were hard-impact landers which were not intended to continue providing useful data after their high-speed landings. The Huygens probe, being carried to Saturn's moon Titan by the Cassini probe, is likewise not specifically designed to survive landing. However, due to the low speed with which it is expected to impact, it is expected to continue providing data for a short while after landing, and even to float should it touch down on one of Titan's hypothesized ethane lakes.

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 of which successfully touched down. The Soviet Vega program also placed two balloons in the Venusian atmosphere.