Edited by author 09-11-2002 03:58 AM
Blame Article 6 of the Outer Space Treaty of 1967:

States Parties to the Treaty shall bear international responsibility for national activities in outer space, including the Moon and other celestial bodies, whether such activities are carried on by governmental agencies or by non-governmental entities...

It also says:

Outer space, including the Moon and other celestial bodies, is not subject to national appropriation by claim of sovereignty, by means of use or occupation, or by any other means.

...meaning America can never have a Martian state. (Unless we withdraw from the treaty.) Fun stuff.