A cargo spacecraft arrived at the International Space Station on Saturday, but shortly after Russian cosmonauts opened the hatch, they had to slam it shut again. The cosmonauts noticed a strange stench coming from the Russian Progress 90 spacecraft, which brought a load of food and equipment. They also "observed small droplets" coming from the cargo ship, which raised fears of a contamination hazard, reports Gizmodo. The Poisk hatch was immediately closed to the rest of the Russia segment of the ISS, while "space station air scrubbers and contaminant sensors monitored the station's atmosphere," NASA officials said Sunday. Air quality was found to be normal, meaning "there are no concerns for the crew."
In a Monday statement, NASA said the odor and droplets likely resulted from "outgassing from materials inside the Progress spacecraft," per CNN. Outgassing is the process by which materials release trapped gases when exposed to a vacuum, as in space. A NASA rep noted "any detailed information on what caused the unusual odor" would have to come from the Russian space agency. "The crew reported the odor dissipated quickly and cargo transfer operations are proceeding on schedule," the statement added, indicating the cosmonauts had been able to access Progress' three tons of supplies. The ship will remain docked at the ISS for about six months, collecting trash, before it departs to burn up in the atmosphere, per Gizmodo. (More International Space Station stories.)