As space agencies prepare for longer missions to the Moon and eventually Mars, protecting astronaut health has become increasingly important. One of the biggest concerns is exposure to high levels of cosmic radiation outside Earth’s protective magnetic field, which can damage DNA and increase the risk of cancer.

Researchers are also investigating another possible contributor to cancer risk during spaceflight, disruption of the body’s internal biological clock, known as the circadian rhythm. The circadian rhythm regulates many essential processes, including sleep, metabolism, cell division, and DNA repair.

Researchers from NASA GeneLab for High Schools and Rensselaer Polytechnic Institute reanalyzed RNA sequencing data from the lungs of mice that had spent time aboard the International Space Station. Their goal was to determine whether spaceflight alters the activity of genes involved in the circadian clock and whether these changes could affect the body’s ability to repair radiation-induced DNA damage.

The researchers examined publicly available RNA sequencing data from NASA’s GeneLab repository and identified six circadian genes whose activity changed after spaceflight. Among the most notable were Arntl and Npas2, which showed increased activity, and Per3, which showed reduced activity. These genes help regulate the body’s biological clock and play important roles in controlling cell growth, cell division, and DNA repair.

When DNA damage occurs, cells normally activate repair pathways that prevent harmful mutations from accumulating. If these repair systems are disrupted, damaged cells are more likely to survive and eventually become cancerous. The researchers propose that changes in circadian gene activity during spaceflight could reduce the efficiency of these repair mechanisms, making radiation damage more harmful.

The findings also suggest that circadian rhythm disruption caused by altered light cycles, stress, and other aspects of space travel may work together with cosmic radiation to increase cancer risk during long-duration missions. Understanding how these factors interact could help researchers develop better strategies to protect astronauts traveling beyond low Earth orbit.

Beyond space exploration, the research also highlights the value of RNA sequencing for understanding how environmental conditions influence gene activity. By measuring changes in gene expression across thousands of genes simultaneously, RNA sequencing allows scientists to uncover biological pathways that may not be apparent through traditional laboratory testing.

Although the research was performed using mouse lung tissue and requires additional validation, it provides new insight into how spaceflight affects circadian biology. As human exploration moves farther into space, studies like this may help guide the development of countermeasures that reduce long-term health risks for astronauts.