EVA is an abbreviation for extravehicular activity, meaning activity in space outside a spacecraft. The popular term for it is spacewalking. The Soviet cosmonaut Alexei Leonov made the first EVA in March 1965, followed a few weeks later by the US astronaut Edward White. White practised manoeuvring himself with a jet 'gun'. His was the first of several EVAs in the Gemini series of flights.
The early EVAs proved that, properly protected with a spacesuit against the hazardous environment of space, human beings could carry out useful work in orbit outside their craft. This has since been proved many times over: spacewalking Skylab astronauts saved that space station project by carrying out vital repairs following damage sustained during launch; Soviet cosmonauts have carried out lengthy EVAs to maintain their Salyut and Mir space stations; shuttle astronauts have demonstrated great versatility on EVA by recovering, repairing and relaunching satellites in orbit. For transport they 'fly' the MMU (manned manoeuvring unit), which has been described as a jet-propelled armchair.
The Apollo astronauts carried out a different kind of EVA - walking on the Moon. Neil Armstrong pioneered lunar EVA when he stepped down on the Moon in July 1969. With fellow astronaut Edwin Aldrin, he developed the 'kangaroo lope' as a means of walking in the low-gravity lunar environment. Ten other US astronauts planted their footsteps on the Moon before the Apollo landings ended in December 1972. Undoubtedly, astronauts will return to the Moon early next century and set up a permanent base there. This base could provide a stepping stone to the manned exploration of Mars that should follow, perhaps in the 2020s. Astronauts should find Martian EVAs easier to manage, because Mars's gravity is more than double the Moon's.
