0.1 Why in News

0.1.1 Recent studies published in Science (2 January 2026) and Proceedings of the National Academy of Sciences (12 January 2026) report that spaceflight alters immune gene expression and deforms brain structure.
0.1.2 Findings are significant for long-duration missions to the Moon and Mars.

0.2 Impact on Immune System

0.2.1 Human immune cells (THP-1 monocytes) were sent to the International Space Station for study.
0.2.2 The space environment significantly altered gene expression in these cells.
0.2.3 Genes related to heart function became overactive.
0.2.4 Genes related to the nervous system became overactive.
0.2.5 Genes related to vision and smell became overactive.
0.2.6 Genes responsible for DNA repair worked less efficiently.
0.2.7 Genes involved in cell division worked less efficiently.
0.2.8 These changes indicate potential long-term health risks for astronauts.

0.3 Impact on Brain Structure

0.3.1 MRI scans of 26 astronauts were analysed before and after space missions.
0.3.2 Results were compared with a control group of 24 participants in a head-down tilt bed-rest study.
0.3.3 During spaceflight, different regions of the brain showed reversible movement and deformation.
0.3.4 Brain regions responsible for movement and sensation showed the maximum shift.
0.3.5 In astronauts who spent about one year in space, the supplementary motor cortex shifted upward by approximately 2.52 mm.
0.3.6 Greater shifting of the posterior insula was associated with poorer balance performance after return to Earth.

0.4 Limitations of the Study

0.4.1 Sample size of astronauts was limited.
0.4.2 Bed-rest experiments could not fully replicate the effects of microgravity.
0.4.3 The exact reason for the link between brain region shifts and performance decline remains unclear.

0.5 Significance

0.5.1 Highlights physiological risks associated with long-duration space missions.
0.5.2 Underlines the importance of understanding microgravity effects on human health.
0.5.3 Provides inputs for planning future human space exploration missions.