The Mariner program, a series of missions which aimed to visit Venus and Mars, was ambitious. Its beginnings, however, were somewhat lackluster. The first Mariner spacecraft was lost during launch. In the early days of space exploration, NASA scientists and engineers learned that risk would continually accompany their pioneering efforts.
Risks paid off, and what was once merely speculation about distant planets was being verified with an abundant science return, courtesy of an impressive instrument package. Mariner 2 carried six instruments, including a microwave radiometer, an infrared radiometer and a cosmic dust detector.
Mariner 2 could pat itself on the back for many "firsts." In addition to being the first spacecraft to cruise interplanetary space, it also measured solar wind for the first time. This elusive stream of charged particles emanating from the Sun could hold keys to the formation of the universe. Mariner 2's legacy paved the way for NASA's Genesis spacecraft, currently on its way to gather particles of the solar wind and bring them back to Earth for research.
With its cosmic dust detector, the spacecraft also measured interplanetary dust and found that it was not as plentiful in space as scientists had expected. Mariner 2 also identified several brief solar flares and cosmic rays from outside the solar system.
The microwave and infrared radiometers allowed Mariner 2 to effectively "see" through the multitude of clouds that cover Venus' surface. It revealed a hostile, hot environment made up mostly of carbon dioxide.
JPL's Mariner missions continued until Mariner 10 in 1975. Without their ground-breaking adventures, space exploration would not be as advanced as it is today. To land rovers on Mars, NASA first needed to know the most fundamental issues that faced them on the red planet. The Sojourner rover that explored Mars in 1997, and the rover mission that will travel to Mars next year, have the Mariner legacy to thank for beginning the difficult work of investigating other planets.