In late August, astronauts aboard the International Space Station awoke to a message from the ground saying that there could be a leak somewhere on board. Atmospheric pressure was slowly dropping, and the ISS crew spent the next few hours hunting down that leak. Eventually, they found it hiding in one of the Soyuz capsules used to bring supplies and people to the station. The hole was patched, but speculation about how it got there remained.

Today, two Russian cosmonauts—Oleg Kononenko and Sergei Prokopyev—are taking an unprecedented spacewalk to find some answers. During a six-hour mission that started at 11 a.m. Eastern, the two will cut through the outer shell of that Soyuz to get a good look at the hole from the outside.

The spacewalk is being livestreamed on NASA TV, and you can watch it here:

This content is imported from YouTube. You may be able to find the same content in another format, or you may be able to find more information, at their web site.

On the spacewalk, the two cosmonauts will have to use tools to cut through the spacecraft’s thermal insulation and debris shield. This has never been done in space before. According to Roscosmos Chief Dmitry Rogozin, the spacewalk is “unprecedented in its complexity.”

This same Soyuz will later be used to carry three members of the ISS back to Earth next week, and ground crews will finally be able to examine the craft in greater detail. But since the reentry process will likely damage the craft, it’s imperative that cosmonauts get a good look at the outside now.

This investigation is important because there’s a chance the leak could have been caused by a person, perhaps deliberately. The hole does appear machined—at least from the inside—and there are tool marks around it, suggesting that it could have been created with some sort of drill. Rogozin has previously suggested it may have been an act of sabotage, although there doesn’t appear to be any evidence of that yet.

This content is created and maintained by a third party, and imported onto this page to help users provide their email addresses. You may be able to find more information about this and similar content at piano.io