Amidst the scientific progress, big egos, and general madness of the Cold War, the US wanted to drop a nuclear bomb on the Moon. The idea was sold as being in the interest of science, but really it was just a big middle finger to the USSR. As if this cautionary tale couldn't get any weirder, a young Carl Sagan was one of the bright sparks used to hatch the plan.

A declassified report by the Air Force Nuclear Weapons Center from June 1959 shows just how seriously they considered the plan, called Project A119. In essence, they wanted to investigate the capability of weapons in space, as well gain further insight into the space environment and the detention of nuclear devices. 

The report explains: ”The motivation for such a detonation is clearly threefold: scientific, military, and political.” Within the 190 pages, they discuss at length the possible effects on the lunar surface, how they could conduct seismic observations on the Moon during the blast, and how long the radioactive fallout might last.

Their idea was to drop a small W25 nuclear warhead along with the Moon’s terminator (the division between the illuminated and shadowed parts). This means the mushroom cloud would be lit up by the Sun and could be seen from Earth and, in particular, viewable from Moscow. All of their research showed they did indeed have the technological clout to pull this off. The bomb would have boasted a 1.7-kiloton yield. That's relatively low for an A-bomb, but it's still no joke.

 

The grand plan of Project A119 was led by Dr Leonard Reiffel (who later became the deputy director of NASA’s Apollo program), high-ranking officials in the US Air Force, and a few of the West’s top scientists, including Gerard Kuiper, a major figure in modern planetary science.

Carl Sagan, the legendary science prophet, also worked on the project. Years before he became an outspoken critic of nuclear weapons, he was employed by Reiffel to work out how big and visible an exploding dust cloud in the space around the moon would be. Sagan's name even appears on the report’s list of contributors at the top of the declassified report.

In fact, this story only came to light because author Keay Davidson was doing research for a biography about Sagan, called Carl Sagan: A Life in the late 1990s. Davidson kept it quiet, but the information was eventually published in a review of the book in Nature. Once the cat was out the bag, Reiffel was the first person to officially “go public” about the plan in 2000.

In an interview with The Observer shortly after the plan was revealed, Dr Reiffel said that science had little to with this eccentric plan. In the heat of the Cold War, this was about flexing muscles.

“It was clear the main aim of the proposed detonation was a PR exercise and a show of one-upmanship. The Air Force wanted a mushroom cloud so large it would be visible on Earth,” Reiffel said. “The US was lagging behind in the space race.”

Thankfully, the plan never came to fruition. They eventually put the brakes after fearing what the public’s reaction would be. 

"I made it clear at the time there would be a huge cost to science of destroying a pristine lunar environment, but the US Air Force were mainly concerned about how the nuclear explosion would play on Earth," Reiffel added.

It’s believed the USSR had a similar plan to A119, although next to nothing is known about it. Even so, it's very likely their plot was a rushed response to hearing about US plans.

Nowadays, there are a fair few steps in place to stop countries using the Moon as their nuclear weapon playground, just in case it wasn't common sense. The Partial Nuclear Test Ban Treaty in 1963 and the Outer Space Treaty in 1967 both mean you cannot detonate a nuclear device on or around the Moon.