The longer astronauts spend in space, the more their bodies tend to change—sometimes in undesirable ways. Long-term space flight has been linked to muscle and bone loss, vision problems, and even an overactive immune system. Now, a new study confirms bacteria aboard the International Space Station (ISS) are undergoing changes of their own. The difference is that they might actually be growing stronger in space. Data collected over 8 space flights tracked the evolution of strains of Acinetobacter pittii from the ISS. opportunistic bacteria perhaps best known for causing hospital-acquired infections on Earth. Findings revealed that these cosmic strains (red box) have become genetically distinct from strains found on Earth, even evolving functions that could help them thrive in space, such as a mechanism for repairing DNA damaged by radiation. One of the most concerning changes is the ISS strains’ ability to resist antibiotics such as cefepime, which are typically effective against infection on Earth. These signs point to the possibility that A. pittii is learning to thrive under the harsh conditions of space, which calls for close attention to these and other microbes that share living quarters with spacefaring humans.