Elon Musk tweeted "Nuke Mars" on Thursday.

Musk has championed the idea of launching nuclear weapons just over Mars' poles since 2015. He believes it will help warm the planet and make it more hospitable for human life.

The idea is to release the CO2 trapped inside Mars' ice caps, producing a greenhouse effect.

A study done in 2018 concluded that using Mars' CO2 to replicate the Earth's atmosphere would be impossible with today's technology.

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Elon Musk tweeted on Thursday evening "Nuke Mars." A few hours later he followed it up with "T-shirt soon."

Although the tweet is in Musk's typically flippant style, the billionaire has long championed the idea of firing nuclear weapons at the red planet with the aim of terraforming it — that is, making the surface habitable for humans.

In an appearance on "The Late Show With Stephen Colbert" in 2015, Musk said Mars could be warmed by dropping thermonuclear weapons (hydrogen bombs) over the poles, prompting Colbert to call him a "supervillain."

He elaborated a few weeks later at an event for his solar-panel company Solar City, saying the aim would be to create two miniature "suns" over the poles using nukes.

The goal would be to vaporize the water currently trapped in ice at Mars' poles, releasing CO2 into the atmosphere and therefore engineering a greenhouse effect on the planet.

Musk has been extremely vocal about his ambition to establish a human colony on Mars, and it is one of the guiding missions of his space-exploration company SpaceX.

Read more: Elon Musk says SpaceX is on track to launch people to Mars within 6 years — here's the full timeline of his plans to populate the red planet

The science of nuking Mars isn't watertight, however. In 2018, two researchers from the universities of Colorado and Northern Arizona explored the possibility of using CO2 to terraform Mars, and concluded it wouldn't be possible with today's technology.

The study, published in Nature Astronomy, identified two problems. The first is there simply isn't enough CO2 trapped on Mars to produce the intended effect. The second is particles from Mars' atmosphere are constantly being lost to deep space, so vaporized CO2 would leak out of the atmosphere.

Whether Musk will make a T-shirt out of nuking Mars remains to be seen, though his companies do have a long history of selling unusual, and sometimes dangerous, merchandise.

Read more: Elon Musk limits meetings at Tesla to only six people — and made it a rule that employees should "walk out" if nothing's getting accomplished