This morning, the two Russian crew members on board the International Space Station are going on a spacewalk to investigate a mysterious hole that popped up in a visiting spacecraft that caused air to leak out of the ISS a few months ago. The origin of the hole has yet to be determined, and its existence has spawned numerous wild rumors about in-space sabotage. Today’s walk may help officially determine how the hole was made.

The astronauts on the ISS first discovered the hole in late August after flight controllers at NASA noticed that the air pressure was dropping, a sign that air was slowly leaking out of the station. Sure enough, the crew members traced the problem to a hole about two millimeters wide in one of the visiting Soyuz capsules, which is the vehicle used to transport astronauts to and from the station. Astronauts quickly patched the hole with epoxy on a gauze wipe, and the station’s pressure has been fine ever since.

At first, it was thought that the hole may have been caused by a tiny meteorite slamming into the Soyuz. But pictures of the hole showed a particularly clean, round opening — as if it had been made by a drill. And there appeared to be small drill marks next to the hole, too, suggesting the driller had missed a few times. Upon this discovery, Dmitry Rogozin, the head of Russia’s state space corporation Roscosmos, said that an investigation would consider all possibilities for how the hole was made — whether it was done on Earth or in space. That sparked a ton of rumors about possible astronaut sabotage, and Russian tabloids even suggested one of the American astronauts did it to force an evacuation of the ISS to help a sick crew mate.

The speculation got so bad that NASA and Roscosmos released a joint statement that the two organizations were working closely together to figure out the cause of the hole, and assured the public that the entire ISS crew is “dedicated to the safe operation of the station and all docked spacecraft to ensure mission success.”

Currently, the leading theory is that the hole was made while the Soyuz was being manufactured. It’s possible some unknown worker accidentally drilled a hole in the wrong spot, and hastily tried to cover it up before launch. Then at some point — potentially after the Soyuz docked with the ISS — whatever makeshift cover the worker made was jostled out of position, revealing the hole.

No formal conclusion has been made, however, which is why Russia decided to conduct today’s spacewalk. Russian cosmonauts Oleg Kononenko and Sergey Prokopyev will leave the space station around 11AM ET, in order to examine the outside of the docked Soyuz. They will remove the thermal insulation and the meteorite shield on the Soyuz exterior covering the hole, and they will take samples that will be returned to Earth, according to TASS. In fact, this same Soyuz will be responsible for returning those samples when it departs on December 20th with three crew members on board.

NASA is airing live coverage of the Russian spacewalk, which is expected to last up to six hours.