Frequently Asked Questions

1.5.1 How Many Animals and Plants Have Flown in Space?

Throughout the history of space life sciences, the combination of research priorities and practical constraints has led to a veritable menagerie of organisms orbiting the Earth. Some of the more exotic include African claw-toed frogs, Japanese quails, tobacco hornworm pupae, flour beetles, sea urchin eggs, parasitic wasps, and pepper plants (see Ballard and Mains 1990). A more complete list appears in Chapter 2, Section 2.

1.5.2 How Do Animals React to Microgravity?

Through millions of years of evolution, most terrestrial organisms have adapted to function optimally in the presence of a constant, unidirectional 1-g gravitational field. It is therefore not surprising that considerable changes occur at the organism level when the gravitational force is virtually removed.

Do the animals like living in microgravity? Does floating instead of walking confuse them? Amazingly, they adapt very quickly. Within five minutes, mice are floating in their living spaces, grooming themselves, and eating, just as they would on Earth.

Can fish swim in microgravity? Do bees make honey in space? Can ant farms exist on the Space Station? Fish and tadpoles swim in loops, rather than straight lines, because there are no up or down to orient them. If a light shines, the fish use that as their guide source and swim towards the light. Baby mammals have a hard time in space because they normally huddle for warmth. In space, it's hard to huddle when bodies drift and float. It is also difficult for babies to nurse when they can't locate their mother's nipple.

1.5.3 Why Study Microbes in Space?

Microbes are thought to make up more than 60% of the Earth's biomass. They have survived and evolved for over 3.7 billion years and have been found in almost every environment (for a review of microorganisms with particular physiological and nutritional characteristics, see Clément 2005, Chapter 2, Table 2-01). The diversity and range of environmental adaptations exhibited by microbes makes them a natural choice for studying how terrestrial life adapts to unique environmental pressures, such as those found in space. In addition, they are easy to grow and handle and most microbes are not responsible for diseases in humans, animals, or plants, making them relatively safe to study in a closed environment. Though microbes such as the bacteria Escherichia coli (E. coli) (see Chapter 2, Section 3.1) are used extensively to study basic biological processes in space, including cell growth and metabolism, they are also of considerable interest to bioengineers keen to exploit their waste recycling potential in bio-regenerative life support systems.

Microbes are also making a contribution to nanotechnology advances being developed to support space exploration. For example, NASA scientists are using a genetically modified strain of E. coli to produce large quantities of proteins that sticks to gold or semi-conductors. The protein can be crystallized to form nano-templates about 5,000 times smaller than the width of a human hair (Figure 1-06).

Figure 1-06. Certain organisms, such as E. coli shown here, have become "model organisms" in research laboratories because of advantages in studying them. E. coli reproduces rapidly (under optimal situation 0.5 h/generation) such that results for a number of experiments can be quickly obtained. Certain mutants ofE. coli have been defined that cannot express certain proteins at saturation growth, and, therefore, die. Also, it is easy to manipulate both genetically and biochemically. E. coli's ability to take up exogenous genetic material under the procedure known as DNA-mediated cell transformation has also made it a popular model for studies using recombinant DNA. Most importantly, it shares fundamental characteristics, such as DNA and messenger RNA, with all other organisms. Photo courtesy of NASA.

1.5.4 Why Grow Plants in Space?

Plants respond to gravity and to other environmental factors in fundamental ways. By studying plants in the microgravity environment of space, we can begin to understand basic concepts in plant biology, such as perception, signal transduction, and response to stimuli. The spaceflight environment can also be used to specifically elucidate gravity-mediated events, such as gravitropism and circumnutation.

The same qualities that make plants essential to life on Earth—food production, absorption of C02, and release of 02 and water vapor—make them highly desirable on long-term human space missions. Investigations with a variety of organisms also have practical implications to developing life support systems. A Controlled (or Closed) Environmental (or Ecological) Life Support System (CELSS) may be required for space missions of increasing durations and numbers of crewmembers. Such missions may require life support systems relatively independent of re-supplying consumable items, such as food, water, and oxygen. These substances may need to be recycled or regenerated. On Earth, life support systems including higher plants have been studied for at least 20 years and tests with some components have been

Figure 1-07. Jellyfish are aquatic organism with one primary radial axis of symmetry. This photograph of a jellyfish Ephyra shows the organism's gravity-sensing rhopalia. Another common species of jellyfish is Physalia. By reference to the simplistic orientation behavior of this animal our first series of experiments studying human spatial orientation on board the Russian Mir space station was named "Physalie". Photo courtesy of NASA.

conducted on the Russian Mir station and the ISS (for a review, see Eclcard 1996).

On an aesthetic level, plants have been shown to have a positive psychological effect on astronauts, providing some relief from the prolonged confinement of spaceflight and the sterility of the spacecraft environment.

In the sections that follow, the fundamental questions being asked in the various areas of space biology, and the approach to answering them are described.

Figure 1-07. Jellyfish are aquatic organism with one primary radial axis of symmetry. This photograph of a jellyfish Ephyra shows the organism's gravity-sensing rhopalia. Another common species of jellyfish is Physalia. By reference to the simplistic orientation behavior of this animal our first series of experiments studying human spatial orientation on board the Russian Mir space station was named "Physalie". Photo courtesy of NASA.

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