Back in 1967, the superpowers USA, UK and USSR signed the Outer Space Treaty, mutually affirming that none would 'conquer' any 'celestial bodies' beyond Earth's orbit, nor create any military bases there, not even place weapons of mass destruction in orbit. So far, 129 countries signed the treaty, which guarantees access to space for every one of them for the purposes of exploration and scientific research.
However, this treaty says absolutely nothing about commercial exploration of outer space; it binds only governments, not private enterprises. If Elon Musk plants a flag on Mars, will he effectively take ownership of the whole planet? If he starts terraforming Mars, can anyone stop him — and how?
Read the treaty and come to Pip Torok's CC, Alpine Meadow, to discuss it with us!
https://www.unoosa.org/oosa/en/ourwork/spacelaw/treaties/introouterspacetreaty.html