They are being studied on Earth but most likely they don't pose any sort of danger
"And now it turns out that somehow these swabs reveal bacteria that were absent during the launch of the ISS module. That is, they have come from outer space and settled along the external surface. They are being studied so far and it seems that they pose no danger," the Russian astronaut said.Some terrestrial bacteria also survived on the space station's external surface, though they had remained within a space vacuum for three years. In addition to that, they underwent sharp swings in temperature from minus 150 to plus 150 degrees Celsius, he noted.The bacteria were brought to the space station accidentally on tablet PCs together with various materials that are placed aboard the ISS for long periods to study the materials' behavior in outer space.
A Russian cosmonaut claims to have caught aliens. Cosmonaut Anton Shkaplerov says he found bacteria clinging to the external surface of the International Space Station that didn't come from the surface of Earth. Shkaplerov told the Russian news agency Tass that cosmonauts collected the bacteria by swabbing the outside of the space station during space walks years ago. "And now it turns out that somehow these swabs reveal bacteria that were absent during the launch of the ISS module," Shkaplerov told Tass. "That is, they have come from outer space and settled along the external surface. They are being studied so far and it seems that they pose no danger."The cosmonaut is preparing for his third trip to the space station next month. The collection of life forms from the outside of the ISS during one of his previous trips was something of a mini controversy a few years back. Russian scientists reported that spacewalk sample harvests yielded evidence of apparent sea plankton clinging to the station. The claims caught NASA by surprise at the time, which said it had heard nothing from the Russians about any space plankton.
Based solely on Shkaplerov's comments, it's too early to say we have found extraterrestrial life: The station has been in orbit for almost two decades and there are plenty of ways microbes could have sneaked up since the launch. NASA did not respond to a request for comment about the statement, but in 2014, when Russian officials announced that a similar project had found Earthen bacteria on the space station's exterior, NASA was quick to point out they had received no such information.Even the best sterilization techniques can't necessarily remove all traces of life on Earth when an uncrewed mission launches. That's why, for example, NASA was careful to destroy the Cassini spacecraft by sending it plummeting into Saturn rather than risk it touching the planet's potentially habitable moon Enceladus. It's also why when NASA selects target landing and exploration sites for its Mars missions, it rules out places it thinks bacteria could flourish.But sterilization gets even trickier at the International Space Station, which has been in orbit since 1998. The space agencies that participate in the project do what they can to decontaminate supplies and quarantine astronauts, but like any other building that serves as a home for humans, its interior is known to be brimming with bacteria, which NASA monitors. Bacteria are also known to hang out in the upper reaches of Earth's atmosphere, as high as 20 miles above the surface.Shkaplerov, who has spent a year in orbit, will be returning to the International Space Station via a rocket launch scheduled to take place next month.