Lord Martin Rees was interviewed by CBC Radio One, Canada's national public broadcaster.
While some humans might one day live on Mars, the U.K.'s astronomer royal warns that the prospect of a mass migration to the Red Planet is a "dangerous delusion."
"I think we have to accept that there's no planet B, which can ever be made as comfortable as the Earth," Martin Rees told The Current's Anna Maria Tremonti.
"We've got to make the Earth habitable not just now, but for future centuries."
