Experiments and analyses have been designed both on Earth and in space to study the impacts that spaceflight has on human biology and physiology. Subjects vary from plants, cell cultures, non-human animals, and humans. In space, the hazards outlined in Figure 1 are highlighted here as they pose health risks and drive many physiological changes seen during spaceflight. On Earth, these hazards are simulated in different experiments and milieus. For example, bed studies, radiation of cancer patients, and climbers help to mimic some of the hazards experienced in the extreme environment of space and provide some insights on their impacts on human physiology. These experiments involve several analyses across multiple systems including cognition, vision, waste, blood, fluid, and post-mortem tissue measurements. Collectively, these experiments and analyses reveal significant recurrent molecular and cellular features of spaceflight including DNA damage, oxidative stress, mitochondrial dysregulation, microbiome shifts, epigenetic changes, and telomere length dynamics. These features help to understand what drives some of the systemic and physiological impacts of spaceflight.
Research on astronaut health and model organisms have revealed six features of spaceflight biology that guide our current understanding of fundamental molecular changes that occur during space travel.
The features include oxidative stress, DNA damage, mitochondrial dysregulation, epigenetic changes (including gene regulation), telomere length alterations, and microbiome shifts.
Here we review the known hazards of human spaceflight, how spaceflight affects living systems through these six fundamental features, and the associated health risks of space exploration. We also discuss the essential issues related to the health and safety of astronauts involved in future missions, especially planned long-duration and Martian missions.
Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻
