An out of this world social media spat has broken out between the head of Russia's space agency and a former NASA astronaut amid threats over the future of the International Space Station (ISS), a US-Russian venture, after Russia's invasion of Ukraine.
Scott Kelly, who spent a year in space aboard the station, tweeted a screengrab of a deleted tweet by Russian space boss Dmitry Rogozin that called Mr Kelly a "moron" and threatened to pull out of the ISS.
Mr Rogozin's bombastic response came after Mr Kelly criticised Russia's invasion of Ukraine and mocked Russia's increasingly isolated position.
In response, Mr Kelly called Mr Rogozin a "child".
"Get off, you moron!" Mr Rogozin said in the since deleted Tweet. "Otherwise, the death of the International Space Station will be on your conscience."
Mr Kelly wrote in a tweet accompanied by a screengrab of the Russian's tweet: "Dimon, why did you delete this tweet? Don't want everyone to see what kind of child you are?" He was then blocked by Mr Rogozin.
Despite the Ukraine invasion, NASA is continuing its space station partnership with Russia.
The spat had been rumbling for several days with Mr Rogozin increasingly rattled by Mr Kelly's tweets criticising the war.
Replying to a video post by Mr Rogozin of flags of partner nations being removed from Russian rockets, Mr Kelly wrote: "Dimon, without those flags and the foreign exchange they bring in, your space program won't be worth a damn. Maybe you can find a job at McDonald's if McDonald's still exists in Russia."
There are currently four NASA astronauts, two Russian cosmonauts, and one European Space Agency astronaut aboard the ISS.
Officials say they are monitoring the situation with Ukraine ahead of the return of astronaut Mark Vande Hei on a Russian spacecraft.
Last week, a video showing Russian cosmonauts floating inside the space station waving goodbye to NASA astronaut Vande Hei, who is supposed to be returning to Earth with them on a Russian Soyuz spacecraft on March 30 after spending a record-breaking 355 consecutive days on the space station.
The American is supposed to be with them on a Russian Soyuz spacecraft later this month.
Russia has stopped supplying rocket engines to the US in retaliation for the sanctions imposed on Moscow by the West last month, with Mr Rogozin suggesting the sanctions could "destroy" US-Russian teamwork on the ISS and claiming it could lead to the space station crashing into earth.
"If you block cooperation with us, then who is going to save the ISS from an uncontrolled descent from orbit and then falling onto the territory of the United States or Europe?
"There is also a scenario where the 500-ton structure falls on India or China. Do you want to threaten them with this prospect? The ISS doesn't fly over Russia, so all the risks are yours."