MARS MANNED MISSION: INTER-GENDER DIFFERENCES AND CREW SELECTION

Manned exploration of Mars is, at present, the most appealing aero-spatial enterprise. The achievement of this target requires great technologic and biologic improvements especially in the fields of human adaptation mechanisms to the space environment and of the study of effective countermeasures against the most frequent pathologies. Moreover, with the steady increase in the number of female astronauts it becomes important to understand the risk of gender-related diseases. This review provides an overview of some known and potential inter-gender differences in physiological responses to spaceflight. The paper covers orthostatic intolerance, bone demineralization, renal stone risk, reproduction and cancer risk. Frequently, in literature, statistically significant conclusions regarding the possible incidence of spaceflight-related health effects cannot be drawn because of the small population who have flown in space. The only astronauts health issues for which sufficient data have been collected to allow valid conclusion about gender-specific differences are the post-flight orthostatic intolerance and the sensitivity to radiation carcinogenesis. Female astronauts have a significantly higher incidence of presyncope during post-flight stand test and a greater potential risk to develop radiation-induced cancers. For these reasons, the crew selection for long-duration space missions, such as Mars exploration, has to take into consideration the major relevance of inter-individual differences on the gender specificity and to evaluate very strictly the individual risks. Human beings have had a nearly continuous presence in space in the last decades. Now they are at the threshold of manned exploration of planets in the solar system. Mars manned exploration is presently the greatest aero-spatial plan and enterprise, attracting the interest of all Spatial Agencies. To achieve this goal, technologic advances in materials science, robotics and power generation will be necessary. There is every reason to believe that, with an adequate monetary support, these targets can be reached. Much more difficult is to make progress in biologic tolerance to the space environment. The longer the flight lasts, the more dangerous life in space for the crew health is. Virtually every organic system functions differently in the absence of gravity, but some changes are maladaptive. Astronauts travelling to Mars will live in the absence of gravity for more than 1 year for the flight and will have to pass between weightlessness and planetary gravitational forces at the beginning, middle and the end of the mission. It has recently been proposed [1] to create an entirely female crew for the manned mission to Mars. The issues considered in the paper were the lower mass and volume of women, the smaller use of consumables and the non-confrontational approaches used in interpersonal dynamics.  This is not really a novelty, since in 1960 also the U.S. Air Force ARDC (Air Research and Development Command) proposed the “Woman in Space Program" with similar considerations [2; Fig.1]. Generally, investigations of physiological responses to microgravity have not been aimed at examining gender-specific differences in the astronaut population. However, many Authors, identified one or more potential inter-gender physiological differences, particularly in some field.