Venting seen earlier was attitude control system fuel.
Welcome to Earth ISS Expedition 53 crewmates[quote/]https://twitter.com/igor29768/status/941236027842326529
Roscosmos cosmonaut @SergeyISS arrives at the Karaganda Airport in Kazakhstan airport after he, NASA astronaut Randy Bresnik and, ESA astronaut Paolo Nespoli landed in their Soyuz MS-05 spacecraft in a remote area near the town of Zhezkazgan, Kazakhstan.
After 139 days in space and a landing halfway around the world, @AstroKomrade & @astro_paolo returned to Ellington Airport in Houston, Texas, to see family, friends, and colleagues for the first time and participate in research and rehabilitation.
https://www.energia.ru/ru/news/news-2017/news_12-14_1.html