Antarctica isn't exactly "protected" the treaty is the outcome of countries that didn't want to give up their claims to Antarctica but also weren't in a position or had the slightest will to actually develop their claims.
The treaty doesn't really protect Antarctica from anything other than nuclear tests, in the future if countries want to actually develop claims it can and will be revisited. That said there isn't much interest in this atm mostly because we do not have the technology and we aren't that desperate heck even if the largest oil field in the would would've been found there no one atm would try to develop it as it would most likely be financially non-viable but nothing would really stop anyone from doing so.
Outerspace on the other hand defines the universe as the heritage of all mankind where no one can claim any stake, which will shortly be changed probably to something along the side of what was used to be used in the US during expansion, where claims would be made by private individuals and corporations rather than countries.