In the forthcoming decade, NASA and the China National Space Agency (CNSA) are projecting crewed expeditions to Mars.
This ambitious endeavor necessitates extensive meticulous planning, comprehensive research, and proactive identification and mitigation of all anticipated challenges. Foremost among these considerations is the health and safety of the astronauts.
Beyond the inherent risks associated with extended interstellar transit, such as radiation exposure and the deleterious effects of prolonged microgravity, the unique environment of Mars itself presents a distinct set of obstacles.
In addition to the elevated radiation levels, the gravitational pull on Mars is approximately 38% of Earth’s gravitational force.
This diminished gravitational field poses potential long-term health implications. A collaborative international research consortium is currently investigating the ramifications of Martian gravity on a pivotal aspect of human physiology: skeletal muscle.
This particular muscle tissue, which constitutes the most substantial tissue in the human organism, comprising over 40% of overall body mass, plays a critical role in locomotion and metabolic well-being.
Furthermore, this tissue exhibits heightened sensitivity, and a reduction in gravitational force could potentially precipitate a significant decline in muscular strength, volume, and functional capacity. Consequently, it is imperative to ascertain the resilience of this muscle tissue within the Martian milieu.
The scientific cohort comprised researchers affiliated with the Institute of Medicine at the University of Tsukuba, the Tohoku Medical Megabank Organization, the Advanced Research Center for Innovations in Next-Generation Medicine (INGEM), the Beth Israel Deaconess Medical Center, the Brigham and Women’s Hospital, the Space Environment Utilization Center of the Japan Aerospace Exploration Agency (JAXA), and a spectrum of academic institutions.
For their experimental protocol, the research group examined the impact of reduced gravity on skeletal muscle tissue in a cohort of 24 laboratory mice, which were transported to JAXA’s Kibo experimental module.
These mice were subsequently housed within a JAXA-engineered centrifugal apparatus, designated the Multiple Artificial-gravity Research System (MARS), where they were subjected to four distinct gravitational conditions – microgravity, 0.33 g, 0.67 g, and 1 g – over a 28-day observational period.
Prior to their orbital deployment, the mice underwent pre-flight assessments at NASA’s Kennedy Space Center, the same location to which they were returned for post-flight sample acquisition.
These acquired biological samples were subsequently subjected to rigorous scientific examination by researchers at the Metabolism and Muscle Biology Lab (MMBL), situated within the Department of Nutrition at the University of Rhode Island (URI). As articulated by Professor Marie Mortreux, who spearheads the MMBL, in a recent publication by Rhody Today:
“While simulating spaceflight conditions for human subjects on Earth is achievable, the process is exceedingly intricate and resource-intensive. We possess centrifuges capable of temporarily exposing human participants to specific gravitational levels; however, this exposure is neither uniform nor continuous.
We employed gravitational gradients that were equitably spaced to obtain a more precise comprehension of the dose-response relationship of each physiological system to gravity. The experimental subset exposed to 0.33g exhibited conditions remarkably analogous to Martian gravity (0.38g). Our findings from this specific group can be extrapolated to inform actionable strategies conducive to enabling Martian exploration.”
Upon the return of the mice to NASA’s Kennedy Space Center, Mortreux and her team meticulously analyzed metrics pertaining to their body mass, muscular strength, and locomotive capabilities. Their analyses revealed that a gravitational force of 0.33 g effectively mitigated spaceflight-induced muscle wasting, with complete prevention observed at 0.67 g.
Furthermore, the assessment of the mice’s forelimb grip strength, facilitated by electrical impedance myography (EIM), indicated that a gravitational level of 0.67 g was sufficient to maintain optimal muscular performance.
Collectively, these experimental outcomes substantiated that 0.67 g represents a critical threshold for effectively counteracting muscle atrophy resulting from protracted periods in spaceflight.
Additionally, an examination of the mice’s blood plasma yielded the identification of 11 distinct metabolites exhibiting gravity-dependent alterations, suggesting their potential utility as biomarkers for tracking physiological adaptations in astronauts.
This research builds upon prior investigations conducted by Montreux, in collaboration with Professor Mary Bouxsein (a co-author of the present study) at Harvard Medical School.
While Bouxsein was instrumental in developing a terrestrial mouse model simulating partial gravity during the early 2010s, Montreux subsequently established a rat model for partial gravity research during her tenure at Harvard. Consequently, both researchers possess a profound understanding of the differential impacts of varying gravitational forces on musculoskeletal tissues.
“Given that our mission objective was to evaluate gravity as a continuous spectrum, we were optimally positioned to ascertain whether our findings derived from ground-based experiments would correlate with outcomes observed under conditions of reduced mechanical loading in orbit,” stated Montreux.
“Collaborating with an international cohort presented both challenges and considerable excitement. I believe my prior professional experiences in Italy, France, and the United States adequately prepared me for such large-scale collaborative endeavors.”
A significant implication derived from this investigation is the necessity for future Martian missions to incorporate strategies aimed at mitigating skeletal muscle depletion during the extensive journeys between Earth and Mars.
Astronauts are required to undertake regular scientific operations and must maintain their mobility and muscular fortitude. The same imperative applies to their physical health upon their eventual return to terrestrial environments.
These research findings strongly suggest that the incorporation of rotating torus systems would represent a judicious enhancement to any prospective spaceflight architectural designs, drawing parallels with concepts such as NASA’s Non-Atmospheric Universal Transport Intended for Lengthy United States Exploration (NAUTILUS-X) and similar innovative proposals.
This content was initially disseminated by Universe Today. The original publication can be accessed here.
