Here's why:

* Outer Space Treaty: The 1967 Outer Space Treaty, signed by most nations, states that celestial bodies, including planets like Mars, are "the province of all mankind." This means no single nation or individual can claim ownership.

* No Legal Framework: There is no legal framework for claiming ownership of planets or celestial objects.

* International Cooperation: The exploration and potential future development of Mars is expected to involve international cooperation, rather than individual ownership.

While some individuals have made claims to owning the Moon or Mars in the past, these claims are legally invalid and not recognized by the international community.