"I don't know why you're on Mars, but whatever the reason for going to Mars is, I'm glad you're there and I wish I was with you."
That was a part of astrophysicist Carl Sagan's message, recorded a few months before he died in 1996, to the future human inhabitants of Mars.
Some of the earliest science fiction imagined voyages to the Red Planet. We now have the space-faring technology, and getting humans to Mars actually seems within reach. It would certainly involve massive resources and a lot of danger, but some believe the rewards would be massive.