Objectives of Space Biology

Space life sciences research has now been conducted for more than four decades. The continuing interest in studying the way living systems function in space derives from two main benefits of that research. First, in order for humans to engage in long-term space travel, we must understand and develop measures to counteract the most detrimental effects of spaceflight on biological systems (Table 1-02). Problems in returning to normal gravity environment on Earth must also be kept to a manageable level.

• Vestibular changes leading to space motion sickness

• Redistribution of body fluids

• Loss of blood cells and blood volume

• Changes in blood levels of several hormones

• Loss of bone mass and increase in calcium excretion

• Decrease in immune system reaction

• Sleep disorders

• Radiation exposure

• Psychological and social issues_

Table 1-02. Physiological changes which could endanger the crewmembers during long-duration space missions (see Clément 2005 for review).

Ensuring the health and safety of astronauts is a continuous priority to which the study of different organisms makes valuable contributions. Evaluating the risks posed by conditions in space and developing effective countermeasures requires an understanding of the short and long-term effects of exposure to such unique conditions. For example, how much shielding is required to reduce the risk of genetic mutations as a result of ionizing radiation? What causes the process of bone demineralization observed in humans and animals during spaceflight and is it possible to control its gene expression? Controlled experiments using different organisms complement

Figure 1-04. On the Space Shuttle Discovery's flight deck, astronaut Stephen K. Robinson uses a cotton swab to collect a saliva sample for microbial analysis. Photo courtesy of NASA.

human studies to address these questions and reduce risk. In addition to the chronic effects of the space environment, acute medical care of astronauts is also important, particularly to support missions to the Moon and Mars. An understanding of how healing processes such as bone and muscle repair and immune responses to infection are affected by the spaceflight is critical, as is pharmacological knowledge of how space travel influences responses to drugs such as anesthetics and antibiotics (Figure 1-04).

Figure 1-04. On the Space Shuttle Discovery's flight deck, astronaut Stephen K. Robinson uses a cotton swab to collect a saliva sample for microbial analysis. Photo courtesy of NASA.

Second, increasing our understanding of how organisms function in reduced gravity gives us new understanding of fundamental biological processes. Throughout its evolution, life on Earth has experienced only a 1-g environment. The influence of this omnipresent force is not well understood, except that there is clearly a biological response to gravity in the structure and functioning of living organisms. To better understand a system, the scientific method set by the physiologists in the 19th century consists of studying the consequences of its exclusion. So, the removal of gravity is a desirable, even necessary, step toward understanding its role in living organisms. Although techniques exist on Earth to increase the gravitational force by using centrifuges, or to reduce its effects by immobilization, slow rotation, or unloading, the effects of prolonged microgravity and cosmic radiation cannot be studied on Earth. While the effects of gravity are fairly obvious at the total organism or system levels, as observed in astronauts, they are not immediately apparent at the cellular level. In addition to this fundamental question of the role of gravity at cellular level, it is also interesting to know if the responses observed in organs or individuals can result from changes produced at the cellular level. The information gained from this research can be used to improve human health and the quality of life on Earth (Planel 2004).

Finally, studying the way in which various plants, animals, and microorganisms interact in closed ecosystems will be essential for developing the advanced life support systems needed for long duration missions. In Earth's orbit, spacecraft can be continuously replenished. Exploring other planets and celestial bodies, however, will require the development self-sustaining ecosystems. The bio-regenerative properties of plants and microbes will be essential factors in such systems, performing critical functions such as producing food, absorbing C02, and recycling waste. In addition to supporting space exploration, research into these properties should produce many benefits here on Earth.

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