But more than anything, human missions are symbolic.
Since then more than a thousand technical designs for human missions to Mars have been authored.
China also announced that it was considering human missions to the Moon.
For decades, Britain has had little to do with human missions.
This applies also to the scientifically sterile space station and to the proposed human missions to the Moon and Mars.
For decades it refused to have anything to do with human missions, preferring to focus on satellites and robot probes.
A fleet of heavy-lift rockets would be developed for both robotic and human missions beyond low orbit.
It asks the space agency to focus on private-sector transport to the space station and long-distance human missions.
The research is intended to help the US space agency and its partners develop plans for eventual human missions to Mars that will last at least two years.
The flows could be used to find water sources on Mars, making them prime spots to hunt for life, and to land future human missions.
If so, there may be an enormous amount of ice on Mars apart from the poles, potentially providing a convenient resource for human missions.
