Yes, lassoing an asteroid and eventually getting humans to Mars is going to be expensive. But look at it this way: Being overly reliant on Earth, as we currently are, probably isn't going to work out for us in the long run.
Appearing at the Humans to Mars Summit 2014 in Washington, NASA administrator Charles Bolden spoke Tuesday in defense of the space agency's ambitious plans for landing a man on the Red Planet by 2030. “We today are Earth-reliant,” he explained. “We are dependent on being on this planet. We are not a multi-planet species yet." Of the many things he and Buzz Aldrin agree on, he added, "one of them is that only multi-planet species survive for long periods of time.”
“Here in the Western world, we think very short-sighted," Bolden continued. "We think about the time in which we are going to be on this Earth, or in which are kids or grandkids are going to be on this Earth. Many other civilizations think much longer than that, and we need to start thinking that way.”
“If this species is to survive indefinitely," on the other hand, "we need to become a multi-planet species.” Getting to Mars, Bolden said, will be a "stepping stone" -- first we need to get there, then we (or our descendants) can start talking other solar systems and galaxies.
It's a rather disheartening message to deliver on Earth Day, of all days. But given the current trajectory of climate change, he just might have a point.