Marsimulator: a device providing continuous low doses of gamma-rays mimicking exposure to the space environment during long-duration space missions.

Space experiments involving biological investigations have generated considerable interest worldwide. Many space experiments have been scheduled for the established experimental area in the International Space Station (ISS), where astronauts and experimental subjects are exposed to both space radiation and microgravity. Both these conditions are difficult to simulate at ground level. Space radiation is comparable to chronic low-dose exposure. It is now well demonstrated that when cells, organs, or entire organisms are exposed to radiation at low doses or at low dose rates, an adaptive response may be observed. We have elaborated an innovative device allowing chronic radiation exposure to be combined with altered gravity. Given the limited access to the International Space Station, this device could be useful to researchers interested in the field of space biology. The magnitude of the Earth's gravity vector cannot be changed but its effect on biological systems can be modified and microgravity simulators may generate functional near weightlessness of a cell or organism. These kinds of devices are very useful for studying the influence of gravity on biological organisms or to prepare and/or complete a study that has been selected to be performed on the ISS. One of these devices is the "random positioning machine" (RPM), which is characterized by the randomly changing rotational speed and 3D-direction of a platform where biological samples can be placed. Irradiation was provided by thorium nitrate powder, conditioned so as to constitute a sealed source that could be placed in an incubator. Cell plates or plant seedlings could be placed in direct contact with the source or at various distances above it. Moreover, a random positioning machine (RPM) could be positioned on the source to simulate microgravity. . Using the RPM placed on the source, we reached a mean absorbed dose of gamma rays of 0.33 ± 0.17 mSv per day.