Mashable wants to know (along with NASA researchers) just what kind of critters are sticking to the International Space Station or surrounding it like an invisible cloud of living things:
Despite the U.S. space agency’s stringent spacecraft cleaning process, hardy microscopic lifeforms can’t be totally removed from instruments bound for space. Furthermore, people carry veritable ecosystems of life on their skin and in their bodies when they go to space. Humans can’t help but spread this stuff — a point John Grunsfeld, NASA’s former chief scientist, emphasized in 2015.
“We know there’s life on Mars already because we sent it there,” he said then.
…
This upcoming station research aims to better understand the potential for microbes to survive and reproduce in space. The study will determine which human-related bugs could inhabit environments on Mars or other destinations in the solar system during crewed missions. The findings could inform changes to crewed spaceships and spacesuits in the future.
Russian space agency Roscosmos has attempted a similar experiment. They have sampled surfaces and announced the discovery of non-spore-forming bacteria growing outside the station. But NASA is skeptical of whether the devices used in the Russian experiment were contaminated and seeks to produce its own data for comparison.