Early Friday morning, Elon Musk tweeted, "Nuke Mars!"

He then said "T-shirt soon," implying one of his companies might make and sell "Nuke Mars" T-shirts.

Musk has discussed the idea of terraforming Mars for years now, which could make it into an inhabitable planet.

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Elon Musk, the CEO of SpaceX and Tesla, still wants to drop nuclear bombs on Mars to transform it into a livable planet for humans — as evidenced by his latest tweet on Friday morning.

Musk believes that by hitting Mars with nuclear weapons, the planet's polar ice caps could melt and release vast amounts of carbon dioxide into the atmosphere, which would essentially create a greenhouse effect that raises the temperature and air pressure of the planet — like a really quick version of climate change.

Musk has shared this opinion for years, dating back to interviews with the billionaire from 2015. He even went on Stephen Colbert's late-night talk show to discuss his idea of bombing Mars — it starts around the two-minute mark:

In 2017, Musk published an article in the journal New Space, detailing how humans could build a 1 million-person colony on Mars in less than a century.

Perhaps in an effort to get more people on board with his idea, Musk floated the idea of selling "Nuke Mars!" merchandise to the Twitter crowd.

It's unclear if Musk is actually serious about the "Nuke Mars!" shirts, but he does seem very serious about making humans an "interplanetary species." His company SpaceX is testing a prototype of its rocket to Mars called Starship, which Musk hopes will eventually send humans to Mars. The prototype for this ship, called Starhopper, just had its first successful test after a previous launch went wrong. NASA is hoping to use rockets from SpaceX for future visits to the moon and Mars.