Elon Musk is now walking back his 'nuke Mars' theory, and instead proposing to launch thousands of satellites to warm the red planet

• Musk has repeatedly posited the idea that Mars' atmosphere could be warmed to accommodate human life by nuking its poles and artificially engineering a greenhouse effect.
• On Tuesday however, Musk suggested that satellites equipped with solar reflectors could be preferable to dropping nuclear weapons.
• Vaporizing Mars' poles is not certain to have Musk's desired effect, as they may not contain enough CO2 to sufficiently warm the atmosphere.
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Elon Musk has a new idea for making Mars' atmosphere more habitable - and it doesn't include launching nuclear weapons at its poles.

Since 2015, Musk has posited the idea that launching thermonuclear weapons above the ice caps at Mars' poles could warm the planet's atmosphere, with the eventual aim of making it habitable for humans. His theory is that vaporizing the water trapped at the poles would release CO2, basically engineering a greenhouse effect.

Read more: Here are some of the gaping holes in Elon Musk and Jeff Bezos' plans to conquer space

Musk reiterated the idea last week and even created "Nuke Mars" T-shirts. On Tuesday however, he tweeted a new theory which replaces hydrogen bombs with satellites.

"Might make sense to have thousands of solar reflector satellites to warm Mars vs artificial suns (tbd)," wrote Musk. Artificial suns is how Musk refers to the theoretical stream of nuclear explosions caused by nuclear bombs.

However, Musk has not fully abandoned the nukes. "Nuke Mars refers to a continuous stream of very low fallout nuclear fusion explosions above the atmosphere to create artificial suns. Much like our sun, this would not cause Mars to become radioactive," Musk said in a follow-up tweet. He also said the method was "not risky imo [in my opinion]."

Replacing nukes with satellites may not address some of the main problems facing Musk's dreams of terraforming Mars. A paper published in Nature Astronomy last year concluded that releasing Mars' CO2 wouldn't be enough to adequately transform its atmosphere for two reasons.

Firstly, the researchers found there isn't enough CO2 trapped in the poles to produce an intense enough greenhouse effect, and secondly unlike Earth, Mars' atmosphere is continuously being lost, so any gases produced would slowly drift away into outer space.