A spacewalk by two Russian astronauts aboard the International Space Station was canceled at the last minute after mission controllers noticed a spray of white particles leaking from an attached spacecraft.
The astronauts, Sergey Prokopyev and Dmitriy Petelin, had already suited up and depressurized an airlock when their mission was called off by NASA and Russia’s space agency on Wednesday night, at around 9:40 p.m. Eastern time.
They were preparing for a six-and-a-half hour spacewalk before flight controllers in Moscow and Houston observed the “significant leaking of an unknown substance” from the Soyuz MS-22 spacecraft, which was docked to a Russian module of the space station, NASA said in a statement.
The problem, NASA said later, was a coolant leak. Video from the U.S. space agency showed a continuous stream of snowflake-like white particles spraying out of the side of the spacecraft.
The leak, which continued for several hours, did not endanger the two astronauts or the rest of the crew of the space station, which consists of three American, one Japanese and one more Russian astronaut, NASA said.
Russian specialists are working to “evaluate the fluid and potential impacts to the integrity of the Soyuz spacecraft,” NASA said. The Soyuz arrived at the ISS in September, bringing Mr. Prokopyev, Mr. Petelin and the American astronaut Frank Rubio. It is scheduled to return the three to Earth in March and also serves as a “lifeboat” for the space station in the case of an emergency.
Mr. Prokopyev and Mr. Petelin were planning to use Wednesday’s spacewalk to relocate a radiator from one module to another on the space station. Their spacewalk had already been postponed once last month because of faulty cooling pumps in their spacesuits, according to NASA. The Russian space agency, Roscosmos, did not immediately respond to a request for comment.
Last November, a spacewalk by two U.S. astronauts was delayed over concerns that they could be endangered by nearby space debris produced after Russia blew up one of its old satellites in space. In 2019, what would have been the first all-female spacewalk was called off because NASA did not have spacesuits that fit the two astronauts.