SpaceX founder Elon Musk criticizes NASA and Congress in public only very rarely—which isn't surprising given that NASA has supported his company with more than $3 billion in contracts for cargo and crew delivery to the International Space Station. But he broke that rule on Tuesday night when asked on Twitter about the new NASA authorization legislation.

"This bill changes almost nothing about what NASA is doing. Existing programs stay in place and there is no added funding for Mars," Musk tweeted. "Perhaps there will be some future bill that makes a difference for Mars, but this is not it," he added.

Musk is absolutely correct on two counts. First, an "authorization" bill does not provide funding. That comes from appropriations committees. Secondly, while Congress has been interested in building rockets and spacecraft, it is far less interested in investing in the kinds of technology and research that would actually enable a full-fledged Mars exploration program.

Much of the general news coverage after President Trump signed the NASA authorization bill on Tuesday focused on the legislation's call for sending humans to Mars. (For example, the AP headlined its story "Trump signs bill authorizing NASA funding, Mars exploration"). However, this perception is probably wrong, as Musk points out. There is lukewarm interest in Congress about aggressively funding humans to Mars—which would cost hundreds of billions of dollars to do using traditional aerospace firms—and according to sources Ars has spoken to, such a costly enterprise holds almost no interest within the Trump administration itself.

It remains likely that Trump, and Vice President Mike Pence, will select Oklahoma Congressman Jim Bridenstine to become NASA's next administrator. Bridenstine is an advocate of lunar exploration in the near term for a variety of reasons, including geopolitical interests and the potential economic value of water ice on the Moon. It is therefore not hard to see why Musk, a Mars enthusiast, might be disappointed with new NASA legislation that keeps the agency on the same course—talking about Mars but not making much progress in getting there.