While reacting to Musk's joint interview with President Donald Trump on Hannity, astronaut Andreas Mogensen challenged the X owner on a claim the Biden administration left two NASA astronauts on the International Space Station for "political reasons."

Mogensen wrote, "What a lie. And from someone who complains about lack of honesty from the mainstream media."

Musk fired back, "You are fully retarded. SpaceX could have brought them back several months ago. I OFFERED THIS DIRECTLY to the Biden administration and they refused. Return WAS pushed back for political reasons. Idiot."

The exchange ended there until Mark Kelly's brother - astronaut Scott Kelly - entered the chat on Friday and dialed up a defense of Mogensen.

Scott Kelly wrote, "was the Commander of the @ISS when Andy, @Astro_Andreas flew his first space mission. He is one of the most competent, trustworthy, and honest people I've ever met. This rhetoric is beyond the pale but, sadly, not surprising. He does not deserve this kind of disrespect."

Musk responded to Scott Kelly by doubling down on his Mogensen criticism and blasting astronaut-turned-senator Mark Kelly.

"Yes, he does. He is an idiot who publicly attacked me, despite having no idea what ACTUALLY happened," Musk said of Mogensen. "Btw, your brother claims to be independent, but is just a Dem donor shill."

The senator fired off a post in which he blasted Musk for never having been to space aboard one of his space company's rockets.

Mark Kelly wrote, "Hey @ElonMusk, when you finally get the nerve to climb into a rocket ship, come talk to the three of us."

Musk had not replied to the senator as of the time of publication.