A spacewalk has been canceled after a leak was discovered on a Soyuz capsule

Updated December 15, 2022 at 4:58 PM ET

A planned spacewalk by two Russian cosmonauts has been called off after ground teams noticed a significant leak from one of the spacecraft docked at the orbiting International Space Station.

The leak originated from the Russian Soyuz spacecraft, spewing a liquid into space for several hours. NASA later said the liquid was coolant.

During their spacewalk, cosmonauts Sergey Prokopyev and Dmitri Petelin were scheduled to move a radiator from an older Russian module to a newer science module that arrived at the station last summer. The spacewalk was called off at the last minute — while the duo were suited up and in the space station's airlock — after ground teams discovered the leak.

The leaking Soyuz capsule transported the two Russian cosmonauts scheduled for the spacewalk, along with U.S. astronaut Frank Rubio, from the Baikonur Cosmodrome in Kazakhstan on Sept. 21.

"When you see it leaking fluid like that, you know something very, very bad is happening," said Terry Virts, a retired NASA astronaut who flew to the station in a Soyuz capsule in 2014.

Ground teams at NASA in Houston and at Roscosmos in Moscow are evaluating the potential impacts on the integrity of the Soyuz spacecraft, which is also responsible for bringing them home. The trio is scheduled to return in the capsule in late March.

But in the short term, Marcia Smith with Space Policy Online says, the spacecraft is also a key piece of safety hardware, like a lifeboat.

"You have to have a way to get off the space station if there's an emergency," Smith said.

It's unknown if they'll be able to use this capsule to eventually return to Earth. Russia may need to launch an uncrewed replacement vehicle.

"There has been pretty much an ironclad rule since the space station got up there that you can only have as many people on board the space station at any one time as you have lifeboats to get them off," Smith said.

A NASA spokesperson said at no point were any of the seven members of the ISS in danger.

"The best plan of action tonight was to focus all of our attention to sorting what's going on exactly with the Soyuz spacecraft and then we'll regroup tomorrow," said NASA Chief Flight Director Emily Nelson.

Russian mission controllers asked the cosmonauts on board the ISS to photograph the coolant leak at the best resolution possible, and instructed the crew not to open certain window shutters on the station. Cosmonaut Anna Kikina used a robotic arm attached to the station to get a closer look at the spacecraft.

Four others are currently on the station: NASA's Nicole Mann and Josh Cassada, Japan's Koichi Wakata, and Kikina. Those four arrived on SpaceX's Dragon capsule on Oct. 5. That capsule is only capable of transporting up to four crew members back home.

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