Extravehicular activity (EVA) is any activity performed by an astronaut in outer space outside of a spacecraft. This includes spacewalks, lunar or planetary surface exploration, and stand-up EVAs (SEVAs) where astronauts stand through an open hatch without fully leaving the spacecraft. EVAs have been conducted by the Soviet Union/Russia, the United States, and China, with astronauts from Canada, Japan, the United Arab Emirates, and the European Space Agency also participating in EVAs conducted by those nations. Since there is no atmosphere in space, the astronaut is completely dependent on the space suit for environmental support.