Lunar Gravity Effects

The effects of chronic lunar gravity on human physiology will be less severe than those of chronic weightlessness, and more severe than those of chronic bed rest at 1 "g". While the long-term effects of microgravity on humans in have been studied since the 1970’s, humans have had only two weeks of exposure to lunar gravity and none to Mars gravity. It seems reasonable that partial gravity will have some benefit, but how much and at what gravity levels is uncertain. Some microgravity effects such as bone loss seem likely to improve as gravity increases, while others such as a sense of up and down seem to appear at a certain level of gravity. Improvements with gravity may be nonlinear and gravity thresholds may occur at different levels of gravity. Is there some gravitational acceleration less than Earth’s that can maintain normal functioning? The physiological responses to long term exposure to moon and Mars gravity are unclear because of the lack of direct data, but Earth experiments can replicate some of the effects of partial gravity.

Richter, Braunstein, Winnard, Nasser, and Weber, investigated “Human biomechanical and cardiopulmonary responses to partial gravity - A systematic review.” The review “summarizes the different effects of partial gravity (0.1–0.4 g) on the human musculoskeletal, cardiovascular and respiratory” systems using lunar data and experiments.

Partial gravity experiments attempt to simulate reduced gravity and its impact on human physiology. Different studies used vertical body weight support, tilted body weight support, parabolic flights, lower body positive pressure, and centrifugation. Partial gravity reduces the work necessary to move the human body which has the long-term detrimental effects of bone loss, cardiovascular deconditioning, and biomechanical changes.

Altered immune cell - endothelium interactions as quantified in partial gravity conditions show similarities to cellular behavior in microgravity. The altered immune functions might increase the risk of infection,

Multiple transitions between gravity levels will occur during planetary exploration missions. In reaction to these gravitational transitions, physiological adaptation will be initiated.