• Elon Musk appeared to smoke pot while taping an episode of Joe Rogan's podcast in 2018.

• One week later, NASA launched a probe into drug use at SpaceX.

• Business Insider obtained the results of the investigation — but NASA redacted them so heavily we don't know what they found.

The National Aeronautics and Space Administration probably knows quite a bit about Elon Musk's drug use, but it won't say what.

The agency spent three months reviewing SpaceX's commitment to a drug-free workplace, among other safety measures, after Musk was filmed smoking a spliff in 2018. Business Insider obtained the results of that investigation under the Freedom of Information Act, but NASA redacted the document so heavily it's impossible to determine what the agency found.