If "venous thrombosis" sounds menacing, that's because it can be—but even more so if you're an astronaut hovering more than 200 miles above the Earth at the International Space Station. Gizmodo reports on just that frightening scenario, as documented in a new paper in the New England Journal of Medicine, in which it's revealed that an unnamed NASA astronaut encountered a major first in space: a blood clot that had stopped the astronaut's blood flow. And not just any type of blood clot, as was determined by an ultrasound done for routine research just two months in to the astronaut's six-month mission—it was in one of the astronaut's internal jugular veins, a rare and "serious event with a potentially fatal outcome."
Although the astronaut felt fine, neither those at the ISS with the astronaut, nor doctors back on the home planet had ever dealt with such a condition in space and had no idea how either the clot itself or anti-clotting drugs would respond there—there was even a possibility the astronaut could start bleeding uncontrollably, and there were no drugs on board to stop that. Thankfully, the anti-clotting meds worked fine, shrinking the clot; it disappeared completely 10 days after the astronaut returned to Earth. "These new findings demonstrate that the human body still surprises us in space," the paper's lead author, Serena Aunon-Chancellor, says in a statement, though the researchers note this incident should serve as a warning for future missions to be better prepared to handle unexpected scenarios like this. (Read more astronaut stories.)