Space Biology What Is It

The space environment inside a pressurized module in orbit is characterized by the absence of effective gravity with the associated condition of microgravity1, the part of the cosmic radiation spectrum that penetrates the

' The term microgravity, or 0 g, is used to describe the environment inside a space vehicle in orbit around the Earth. The experiments inside this vehicle do not

Space Biology is aimed at addressing the basic questions regarding the extent to which gravity plays a role in growth, morphology, and function of cells in the space environment (Cell Biology), ■;' | 'i^k I ■ ■- | ■ : >,|

and from the early fe^ivSg development of animals and .Jk^K^K^ ^Kfif'? sgi '

plants to several life cycles ■pi^/^X ■' (Developmental Biology). More applied aspects of Space

Biology research also include ^^^^^^^H^^^H^^HB^^HT^^ the biological effects of space li^ir ■■. If" , "'¿fy.:

radiation and radiation ^ iMSimW'.-: ^m^^mt walls of the modules and interacts with its materials and inhabitants, and the absence of circadian (24-hour) rhythms. These unique conditions constitute hazards to the safety and proficiency of astronauts and cosmonauts during spaceflight, as reviewed in an earlier book in this Space Technology Series, entitled Fundamentals of Space Medicine (Clément 2005). At the same time, they create unique conditions for the study of vital functions in organisms of varying complexity, from single cells to the most organized species (Figures 1-01 and 1-02).

Transitioning from a terrestrial environment to the space environment has long been known to cause adaptive or maladaptive (i.e., pathological) changes in the human body. Astronauts endure nausea, disorientation a shift in body fluids, disruption of their sleep pattern, depression of their immune reaction, and other conditions as they adjust to life in space. When they return to Earth, most of these conditions disappear, some immediately, some gradually. Some condition, the loss of bone mass for example, can take several years to repair itself, and for some astronauts, the damage may be permanent. The same changes, e.g., modifications in the calcium balance, seem to occur at cellular level.

Neither the 0-g environment nor the complex natural spectrum of space radiation can be produced or effectively simulated in ground-based laboratories. Consequently, studies of the influences of these factors on living organisms can only be studied in space. Both factors have at least two characteristics of exceptional biological interest. Firstly, they have not been encountered by living organisms throughout the entire history of their terrestrial existence and evolution. Secondly, various living organisms display varying degrees of tolerance to each factor, permitting varied and systematic quantitative experiments to determine the nature and extent of their actions. The space environment therefore represents a new and powerful research tool in biology: it makes possible experimental investigations into problem areas in which theory is in no position to make trustworthy predictions (Bjurstedt 1979).

experience a perfect free-fall state. As the vehicle orbits the Earth, it is subjected to small decelerations from atmospheric drag. The location of experiments inside the vehicle is another important factor. Since they are not usually located at the spacecraft center of gravity, a slight mismatch is created between the path of the vehicle orbit and the orbit of an experiment inside. This combination of off-alignment and atmospheric drag alters the free-fall of the experiment. Therefore, near-weightlessness on the order of 10"4 to 10"6 g is more typically experienced in today's spacecraft and is usually referred to as microgravity (with "micro" defined either literally as 10"6, or figuratively as "very small"). For a detailed description of the physics of microgravity and Space Shuttle flight trajectory, see Clément (2005).

Figure 1-02. Belgian Astronaut Frank DeWinne is pictured near a plant growth experiment on board the International Space Station. Photo courtesy of NASA.
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