Jessica Ulrika Meir is an American and Swedish marine biologist, physiologist, and NASA astronaut. She was previously an assistant professor of anesthesia at Harvard Medical School, Massachusetts General Hospital, Boston, following postdoctoral research in comparative physiology at the University of British Columbia. She has studied the diving physiology and behavior of emperor penguins in Antarctica, and the physiology of bar-headed geese, which are able to migrate over the Himalayas. In September 2002, Meir served as an aquanaut on the NASA Extreme Environment Mission Operations 4 crew. In 2013, she was selected by NASA to Astronaut Group 21. In 2016, Meir participated in ESA CAVES, a training course in which international astronauts train in a space-analogue cave environment. Meir launched on September 25, 2019, to the ISS onboard Soyuz MS-15, where she served as a flight engineer during Expedition 61 and 62. On October 18, 2019, Meir and Christina Koch were the first women to participate in an all-female spacewalk. As a member of Expedition 74, during which she took command in July 2026, she made her fifth spacewalk, alongside Christopher Williams on his second, to repair the 58-foot-long Canadarm2 remote manipulator system.