The possibility of humans colonizing outer space may seem like the stuff of science fiction, but British astronomer Chris Impey says that if the U.S. were pumping more money into the space program, the sci-fi fantasy would be well on its way to reality.

"I think we might actually be living on the moon and Mars," Impey tells Fresh Air's Terry Gross. "Maybe not many of us, but we might have our first bases there. We'd have robust commercial space activity or people routinely in orbit. America wouldn't have had a hiatus of four years and counting when we couldn't get astronauts into space. It would be probably quite different."

Impey says the possibility of humans living in space is very real. And if — or when — it happens, the space settlers will face conditions that may cause them to become an entirely new species.

"They'll evolve physiologically quite quickly, because if the gravity is less — as it would be on Mars or the moon — then they will change," Impey says. "Their physical bodies will change even while they're alive. And then if they have children and grandchildren — then they'll change even more."

Impey is a faculty member at the University of Arizona and the author of Beyond: Our Future in Space. In his previous book, Humble Before the Void, Impey recounted his journey to Northern India to teach a program designed to introduce science into the Tibetan Buddhist monastic tradition.\

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