Can our bodies handle a months-long trip to Mars, and what could hurt them?

"Earth-based analogs, including bed rest, dry immersion, and parabolic flights, reproduce many of these effects, linking gravitational unloading to postural instability, orthostatic hypotension, falls, and fractures."

"Strategies such as targeted exercise, optimized fluid management, and even hypergravity interventions may not only safeguard astronaut health but also translate into novel therapies for older adults."

"In particular, spaceflight-induced muscle atrophy/sarcopenia and bone loss, vascular and metabolic changes, hyper and hypo reaction of innate and adaptive immune system appear to be modifications shared with the aging process."

"Most of these modifications are mediated by molecular events that include oxidative and mitochondrial stress, autophagy, DNA damage repair and telomere length alteration, among others, which directly or indirectly converge on the activation of an inflammatory response."

"A number of stress factors, including a prolonged confinement in a limited hermetically sealed space, influence the human body in space on board the spaceship and during the orbital flight. All these factors predominantly negatively affect various functional systems of the organism, in particular, the astronaut's immunity."

"These ground-based experiments allow to elucidate the effect of confinement in a limited space on both the activation of the immunity and the changes of the immune status in dynamics."

"A sealed chamber seems a convenient site for working out the additional techniques for crew members selection, as well as the countermeasures for negative changes in the astronauts' immune status."

"Cosmic radiation, an omnipresent hazard beyond Earth's magnetosphere, accelerates DNA damage and cellular senescence in thymic epithelial cells, impairing thymopoiesis and increasing the risk of immune dysregulation."

"Prolonged exposure to microgravity induces myocardial atrophy and endothelial dysfunction, which may be exacerbated by space radiation."

"Mitochondrial dysfunction and oxidative stress emerge as key underlying mechanisms along with disturbances in ion channel perturbations, cytoskeletal damage, and myofibril changes."

"Disruptions in circadian rhythms caused by factors such as microgravity, light exposure, and irregular work schedules, could further exacerbate cardiovascular issues."

"Human development occurs under the influence of gravity, shielded from space radiation by Earth's magnetic field, and within an environment characterized by 24-hour day-night cycles resulting from Earth's rotation, thus deviating from these conditions necessitates adaptive responses for survival."

"The displacement of fluid from the vascular system to the interstitium, driven by baroreceptor stimulation, results in a 10%–15% decline in plasma volume."

"Exposure of the heart to the proton and heavy ion radiation pervasive in deep space contributes to coronary artery degeneration, augmented aortic stiffness, and carotid intima thickening through collagen‐mediated processes."

"Long‐duration spaceflight has been associated with the prolongation of the QT interval, particularly in extended missions."

"Upon reentry, astronauts frequently experience orthostatic intolerance and altered sympathetic responses, which bear potential hazards in scenarios requiring rapid mobilization or evacuation."

"The four crew members of NASA’s Mars simulation recently marked 200 days into their 378-day Red Planet mission on May 7."

"Spaceflight and partial-gravity environments impose profound challenges to the human musculoskeletal system, driving rapid muscle atrophy, progressive bone loss, and tendon maladaptation."

"Exposure to space radiation remains one of the most significant challenges limiting human exploration activities"

"Crew members also experience mission constraints such as delayed communications, limited supplies, and simulated equipment malfunctions."

"(28 days, 59 days and 84 days, respectively)"

"At the molecular level, unloading suppresses anabolic signaling, enhances proteolysis, and induces mitochondrial stress."

"The GCR environment represents a continuous low dose-rate exposure, leading to appreciable total doses and multiple highly uncertain health consequences"

"During this blackout, the crew works without contact with mission control, using preplanned procedures and available resources to complete tasks and handle any issues that may arise."

"We had no plans and no real capability to carry medical diagnostic or treatment equipment with us back to Earth."

"Although these strategies mitigate some loss, they fail to fully preserve musculoskeletal integrity, particularly tendon properties and microarchitectural bone quality."

"Shielding strategies are largely ineffective at appreciably reducing GCR exposures or risk, and validated model calculations show that too much shielding or poorly chosen shield materials can increase exposures due to nuclear interactions and associated secondary radiations such as neutrons and pions"

"A key objective of NASA’s CHAPEA missions is to gather data on cognitive and physical performance during extended isolation."

"Current countermeasure strategies primarily consist of structured exercise regimens with limited pharmacologic support."

"Risk projections for cardiovascular disease or central nervous system decrements are even more uncertain due to limited (or complete lack of) terrestrial epidemiological data needed to foundationally support such models."

"CHAPEA crew members perform blood collections to monitor their health."

"Key gaps remain in the development of tendon-specific interventions, integrated pharmacologic and exercise regimens, nutrition and dietary protocols, and methods for partial-gravity adaptation and safe re-entry."

"These Skylab experiments confirm that an average fluid loss from the body of nearly 1-1/2 liters occurs within the first two days and that almost all of this fluid may be attributed to having originated from the legs."

"If humans encounter a storm during extravehicular activities or surface operations without adequate shielding, whole body exposures can become elevated enough to initiate acute radiation syndrome responses and possibly death"

"It was suggested that the difference of about 1/2 liter that left the legs, but did not leave the body remains in the upper body, engorging the tissues and vessels above the heart."

"Thus, water and muscle account for 66% of total weight change."

"Skylab offered excellent opportunities for detailed studies of extended space flight effects on man's physiological well being while providing meaningful baseline data for verifying earlier predictions and for predicting the future, longer-duration space flight effects on man."

"The return of body water during recovery requires nearly a week to reach a value similar to the original launch loss before It too levels off."

"The Skylab biomedical experiments were developed to provide systematic investigations and observations of man under controlled conditions to determine his capabilities to live and work for prolonged periods in the space environment."

"All of the changes were of the same order of magnitude as noted in the previous Skylab crews, but the third visit crew returned to normal more rapidly"