Not so fast, Lex Luthor.

Just days after telling the world he still wants to "nuke Mars," SpaceX CEO Elon Musk has slightly walked back the proposal, instead offering a new idea that doesn't use nuclear weapons.

Musk's new plan would use "thousands of solar reflector satellites" in an effort to warm the Red Planet. "Might make sense to have thousands of solar reflector satellites to warm Mars vs artificial suns (tbd)," Musk tweeted.

ELON MUSK LAUDS NEWT GINGRICH'S $2B MOON COMPETITION PRIZE

He followed up with another tweet, saying that his idea to "nuke Mars" refers to "a continuous stream of very low fallout nuclear fusion explosions above the atmosphere to create artificial suns." The outspoken tech exec added that this "would not cause Mars to become radioactive."

When questioned if there were any risks to the plan, Musk told a follower that it was "not risky" and can be adjusted or improved in "real time."

Musk has posited the contentious idea before. In 2015, Musk told Stephen Colbert in an appearance on his television show that in order to make the planet habitable for colonists, the easiest way to insert greenhouse gases and warm the Red Planet would be to drop nuclear weapons on its poles.

Colbert responded by saying, “You’re a supervillain! That’s what a supervillain does!"

In 2018, NASA-backed research said that it was not possible to terraform Mars using present-day technology. "Transforming the inhospitable Martian environment into a place astronauts could explore without life support is not possible without technology well beyond today’s capabilities," the space agency said in a release.

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