space exploration

Note: the original list can be found here.
Reason Number 10
Colonization: it's a long shot, but there are serious people who still claim that we can travel to mars and turn it into livable space for humankind. The process is called "terraforming".
Reason Number 9
Intelligence Surveillance: Ok maybe we wouldn't bother placing a spy satellite over the Hawaiian Tropics contest (then again maybe we would) but the very first truly functional (i.e. non-experimental) satellite was a U.S. spy satellite. This was the Corona series, first operational in August of 1960. The U.S. maintained a strong lead in this super-secret technology throughout the cold war and it was the only distinct intelligence advantage this nation ever really had. Since the U.S. won the cold war, you simply can't dismiss the importance of this capability.
Reason Number 8
International Diplomacy: this one speaks for itself. It's the only reason we went to the moon.
Reason Number 7
Natural Resources: this one...