The tardigrades were transported to the International Space Station by SpaceX’s 22nd commercial resupply mission on June 3, 2021. A minute creature that is capable of forming a tight ball in difficult conditions has been chosen as an object of study to understand how living creatures cope with space.
Tardigrades, whose name means “slow walkers” and which are also called “water bears” owing to their appearance under a microscope, are small invertebrate animals famous for their ability to withstand various forms of stress, including desiccation and freezing.
NASA’s mission report described this experiment as one of a series of scientific investigations carried out in the orbiting laboratory. Known as Cell Science-04, the study examined how tardigrades respond to stress factors in outer space, as well as changes in genetic activity across several generations.
NASA’s Cell Science-04 research overview identifies the experiment’s central objectives as characterizing short-term and multigenerational survival and identifying genes involved in adaptation to stressful environments. Cell Science-04 was designed to improve understanding of tardigrades’ biological processes in space. The investigation used Hypsibius exemplaris , a tardigrade species suited to laboratory research. Scientists planned to examine how its gene expression changed after exposure to spaceflight conditions and compare those changes with results from control samples maintained on Earth. Researchers compared the animals’ initial reactions with those observed after extended periods in space. In a NASA podcast interview , principal investigator Thomas Boothby explained that the team intended to study the first generation after about a week and another generation that had been maintained in space for roughly two months, representing approximately four generations. NASA also explained the potential relevance of this research to astronaut health in its article on microscopic organisms and spaceflight . Studying how tardigrades protect themselves from harsh conditions could help researchers identify biological mechanisms worth investigating for the protection of astronauts during extended space missions. The research, however, did not establish that these mechanisms could directly protect humans. For NASA, the experiment formed part of a broader effort to understand how space conditions affect living systems at the cellular and molecular levels. That knowledge could inform future research as space agencies plan missions that keep crews away from Earth for longer periods. Understanding biological responses to microgravity and other spaceflight stresses is one step toward identifying risks and investigating ways to reduce them. The tardigrades taken to the space station were not simply organisms accompanying a cargo delivery. They allowed scientists to study changes in gene expression in response to the stresses of spaceflight and examine how those responses might differ across generations. Whether the findings can eventually help researchers develop ways to protect astronauts remains an open question.
