Russian cosmonauts Anton Shkaplerov and Pyotr Dubrov were on a spacewalk to investigate a leak in the ISS's Zvezda module.
The coolant, ethylene glycol, was found in a bubble approximately 25 centimeters in diameter on the exterior of the ISS.
The spacewalk was ended prematurely due to the discovery of a toxic coolant leak.
On October 26, 2023, Russian cosmonauts Anton Shkaplerov and Pyotr Dubrov embarked on a spacewalk outside the International Space Station (ISS) to investigate a leak. The leak was first detected in 2019 in the Zvezda module, a crucial part of the station's Russian segment. The cosmonauts were tasked with applying a sealant to the exterior of the module in an attempt to fix the leak. However, during the spacewalk, the cosmonauts encountered an unexpected issue. A blob of toxic coolant was found outside the ISS, which ended the spacewalk prematurely.
The coolant, a substance called ethylene glycol, is used to maintain the temperature of the ISS's systems. It is highly toxic if ingested or inhaled, and can cause severe skin and eye irritation. The cosmonauts noticed the coolant leak when they saw a bubble of the substance growing on the exterior of the station. The bubble was approximately 25 centimeters in diameter.
The cosmonauts were ordered to return to the ISS immediately to avoid any potential harm. The spacewalk was ended after 7 hours and 25 minutes, instead of the planned 8 hours. The source of the coolant leak is still unknown and will require further investigation. The leak in the Zvezda module, meanwhile, remains an ongoing issue for the ISS.