Study of the Biological Dormancy of Aquatic Organisms in Open Space and Space Flight Conditions

In outer space, ultraviolet and cosmic radiation, a wide range of high and low temperatures, altered gravity, electromagnetic fields, the vacuum, and their combinations determine the damaging effect on living organisms and act as a barrier to their interplanetary propagation. At the same time, biological dormancy, known in a wide range of bacteria, fungi, animals, and plants, makes it possible to preserve the viability of their dormant stages under extreme conditions for a long time. Along with lower organisms, resting stages (propagules) of multicellular animals and plants were tested on the ISS from 2005 to 2016 to assess their ability to survive after long-term exposure to open space and space flight conditions. About one-third of the more than 40 species studied were dormant stages of aquatic organisms (Cyprinodontiformes fish eggs, daphnia ephippii, resting eggs of phyllopods and ostracods, and diapausing larvae of dipterans). The experiments were carried out within the framework of four research programs: (1) inside the ISS station (AKVARIUM program) with a limited set of studied species; (2) outside the station in outer space, but without exposure to ultraviolet radiation (BIORISK programs); (3) in modified space conditions simulating the surface of Mars (EXPOSE-R program); and (4) in ground-based experiments with laboratory assessment of the impact of space flight factors (such as neutron radiation) on resting stages. Fundamentally new data were obtained on the tolerance of resting stages of terrestrial organisms to space environment factors, which has changed the idea of the possibility of bringing terrestrial life forms by spacecraft and astronauts to other planets.