The likelihood of living on Mars soon is as remote as Pluto

Some converts are zealous. Some are reluctant. Kelly and Zach Weinersmith are definitely in the second camp. Both, as they constantly remind the reader, are space geeks. But they are also rationalists (who happen to be married). They began writing their new book in the expectation that off-Earth settlements would soon be on the cards. Their rational appraisal, having finished it, is the opposite. Those, such as Elon Musk, who aspire to make Homo sapiens a two-planet species by colonising Mars or somewhere else, are, they conclude, deluding themselves.