Although much can be learned about the surface of a planet from orbiting spacecraft, detailed observations must be made on the surface.
Five Surveyor spacecraft landed on the Moon between July 2, 1966, and January 10, 1968. Each transmitted data to Earth for at least two weeks. The Surveyors photographed the lunar surface and measured its mechanical, electrical, and thermal properties. The last three missions also analyzed the chemical composition of the surface materials.
Two Viking spacecraft landed on the surface of Mars in 1976. The Vikings included instruments for detection of life, chemical analysis, meteorological measurements, and a seismograph. To read about the mission and some of the lander experiment results go to The Viking Mission in the Mars section of the gallery.
Between 1967 and 1983, the (then) USSR sent 12 spacecraft called Venera (4-16) to the planet Venus. Each spacecraft included a lander designed to withstand the intense heat and acidic atmosphere of Venus long enough to make it to the surface and return data. Venera 8, 9, 10, 13, and 14 were among the landers that successfully reached the surface and returned data. All but Venera 8 returned images of the surface. Venera 9 and 10 landed in October of 1975 and returned the first images from the surface of another planet. The above image is from the Venera 14 landing site.
The stationary component of the Mars Pathfinder mission, the Mars Pathfinder Lander set down on the Red Planet on July 4, 1997. Armed with a Stereoscopic Imager and an Atmospheric Structure Instrument/Meteorology package, the lander spent three months investigating the Martian surface, atmosphere, and weather. The Lander also provided support to the mission's rover as a communications relay station and by sending images of the rover's activities back to Earth. By the end of the mission, the lander had sent back 550 images. These images revealed details of Pathfinder's landing site in Ares Vallis, one of the largest outflow channels on Mars.