Did the bet specify that it would be a
human base? If not, and if $1500 is enough to be worth having your school buddy think you have become an idiot or dishonorable, maybe you could have tried to argue that the secret alien outpost [1] on the far side counts and demand that your buddy pay you.
I assume your friend would reject that, but unless the bet specified a procedure to use in the case that the participants could not agree on the outcome, it might have been enough to void the bet at least.
Also, was the bet in writing and signed? If not, and if you are in a jurisdiction that has something like the Statue of Frauds [2], you might try to argue the bet is invalid because the Statue requires contracts that cannot be performed within one year (other than indefinite contracts) be in writing and signed.
The 2010 end date on the contract arguably makes it not of indefinite duration. The "cannot be performed within one year" is harder. It doesn't mean that it has to be performed within a year--just that it is possible.
For example, if I make a contract with you that says I'll pay you $1000 if in the next three years your bicycle is stolen and not recovered within two weeks. Because it is possible that your bike could be stolen in the next year, this contract can be performed in one year. It doesn't matter that it might not be.
Would it be possible in 1990 for a permanent Moon base to be deployed within one year? It may have been physically possible, but it was certainly politically and economically impossible. For Statute of Fraud purposes, is it good enough that it could happen even if it would require worldwide cooperation on an unprecedented scale? Or does it have to have a non-negligible chance of actually happening?
[1] https://www.dailystar.co.uk/news/latest-news/601628/Dark-Sid...
[2] https://en.wikipedia.org/wiki/Statute_of_frauds