The idea of sending humans to Mars has been the subject of aerospace engineering and scientific studies since the late 1940s as part of the broader exploration of Mars. Some have also considered exploring the Martian moons of Phobos and Deimos. Long-term proposals have included sending settlers and terraforming the planet. Proposals for human missions to Mars came from e.g. NASA, Russia, Boeing, and SpaceX. As of 2022, only robotic landers and rovers have been on Mars. The farthest humans have been beyond Earth is the Moon.