Hole in leaky Russian Soyuz spacecraft not caused by Geminid meteor

It's still unclear why a Russian Soyuz spacecraft at the International Space Station (ISS) sprang a leak last week, but one suspect has been ruled out: a strike by a Geminid meteor.

The Soyuz vehicle, known as MS-22, sprayed its coolant into space on Dec. 14, the same day that the annual Geminid meteor shower peaked. But there's no causal connection, NASA and Russian space officials said.

"We did look at the meteor showers that were occurring," Joel Montalbano, NASA's International Space Station program manager, said during a press briefing on Thursday (Dec. 22). "Both the trajectory team in Houston and the trajectory team in Moscow confirmed it was not from the meteor showers; it was in the wrong direction."

Related: Soyuz leak could strand 3 astronauts on space station, expert warns

NASA has been helping Russia's federal space agency Roscosmos with the leak investigation, and not just because both agencies are major ISS partners. This Soyuz brought NASA astronaut Frank Rubio and two cosmonauts to the orbiting lab in September and is scheduled to return the trio to Earth in March.

On Sunday (Dec. 18), NASA used cameras on the station's Canadarm2 robotic arm to inspect the suspected leak area. The survey revealed a small hole in the MS-22, which is the apparent source of the leak. But its origin remains a mystery, officials said.

"We got some work to do with imagery to better understand if it was a meteoroid hit or if there was a hardware issue, and that work is in front of us," Montalbano said.

The now-excluded Geminids are just one class of potential impactors. It's possible, for example, that a piece of space junk punched through the MS-22's hull. Any object capable of making such a tiny hole — it's roughly 0.8 millimeters wide — is too small to be tracked from the ground, said Montalbano and Sergei Krikalev, executive director of human spaceflight programs at Roscosmos, who was also on Thursday's call.

Part of the ongoing investigation is an assessment of the MS-22's flightworthiness. Roscosmos still needs to finish thermal analyses to determine how hot it will get inside the Soyuz during its Earth return, to see if it can safely carry the three spaceflyers home.

It's unclear when such work will be done, though Russian space officials have previously indicated that a decision could come by the end of the month.

If Roscosmos concludes that putting astronauts on the MS-22 is too big a risk, the agency will aim to fast-track the launch of the next Soyuz. That vehicle had been scheduled to lift off in mid-March from the Russia-run Baikonur Cosmodrome in Kazakhstan with three people aboard. Fast-tracking would involve launching it uncrewed a few weeks earlier, perhaps in late February, Montalbano said.

In that scenario, the MS-22 would still come back to Earth, but with no passengers.

"If it's decided that it's an uncrewed Soyuz, Roscosmos would plan to return the current Soyuz on orbit and collect the data so they can use that for future evaluations," Montalbano said.

Mike Wall is the author of "Out There" (Grand Central Publishing, 2018; illustrated by Karl Tate), a book about the search for alien life. Follow him on Twitter @michaeldwall. Follow us on Twitter @Spacedotcom or on Facebook.