Sorry, Elon Musk. The SpaceX founder once said there’s a quick way to terraform Mars: Blast its polar ice caps with nuclear weapons. That would release carbon dioxide, create a greenhouse effect and warm the planet to sustain liquid water and life. But whoa, space cowboy, say scientists whose NASA-sponsored study was published in Nature this week. “Our results suggest there is not enough CO2 remaining on Mars” to blanket the planet, said researcher Bruce Jakowsky, so terraforming won’t work — at least with today’s tech.