If there’s one thing you can say about Elon Musk it’s that he’s never lacked ambition. He’s founded a number of successful companies, and with SpaceX he’s pushed science forward by lowering the cost of entry for satellite launches and opened up new possibilities for researchers.

He’s also seemingly made it his life’s mission to make a human colony on Mars a reality, and he insists that it’s possible to make Mars a lot like Earth as long as we can unlock the carbon dioxide trapped inside Martian ice, rock, and soil. Scientists aren’t fully on board with this line of thinking, but a new tweet from Musk hints that he’s once again ready to argue that “nuking Mars” is a good idea.

Musk’s tweet is a reference to the theory that by dropping one or more large bombs on Mars’ poles, the CO2 locked away in the ice there would be released, giving the Martian atmosphere a much-needed boost:

Nuke Mars! — Elon Musk (@elonmusk) August 16, 2019

Mars has a very thin atmosphere today, but it’s less than one percent as dense as that of Earth. Making the planet’s atmosphere denser could help it retain heat and bring it a small step closer to being habitable by human settlers. However, past research has suggested that bombing the planet’s poles wouldn’t release nearly enough CO2 to be worth the trouble. Elon Musk has publicly disagreed.

It’s unclear why the SpaceX boss decided to bring this all up again, but he does have a habit of saying whatever he thinks will get a big reaction on Twitter. Oh, and apparently he’s hoping to sell some shirts as well.

In any case, no space agency is ready to even begin preliminary planning for a crewed Mars mission, much less any long-term efforts to change the climate of the Red Planet. If that ever does happen, bombs may or may not play a role. In the meantime, scientists will likely maintain that throwing nuclear bombs at other planets is a bad idea.