earlier, this is both costly and risky. Regeneration involves physical/chemical methods for
the synthesis of O 2 from CO 2 , the production of clean water from wastewater, and the
processing of waste (Eckart 1996). However, there are presently no physical/chemical
technologies available that allow the synthesis of food from inorganic material. Bio-
regenerative systems, usually utilizing photosynthetic organisms and supporting engi-
neering components, can provide all of these (Smernoff and MacElroy 1989). Current life
support technologies for space exploration are entirely physico-chemical and are part of
the re-supply philosophy that has served the U.S. space program well for the last several
decades. However, as mission time frames and distances from Earth increase, generative,
biologically based life support systems are increasingly favored over other types (Olsen
1982; Schwartzkopf 1992; Fogg 1995).
In addition to air, water, food, and waste processing, other needs will come to the fore
in a mission of extended length or on a self-sustaining colony. These include usable en-
ergy, materials (especially for construction and manufacturing), pharmaceuticals, and
specialty chemicals. Although mining and chemical extraction of in situresources can
provide some of these needs (Clark 1989; Meyer and McKay 1989; Zubrin and Wagner
1996), biological systems with plants as an integral component eventually could supply
most of them.
Plants have other advantages. Their built-in systems for DNA replication, protein
synthesis, and biomass production can be exploited to maximize mission success. Plants
are solar-powered and naturally self-perpetuating, obviating the need for expensive and
potentially unreliable re-supply missions. An added and very important feature of plants
is that their seeds are small, easy to transport, tolerant of extreme environments, long-
lasting, and contain all the information needed for the subsequent plants to go through
their entire life cycles. With the continued advances in the understanding of the genetic
control underlying plant development and adaptation that can be reliably anticipated in
the next 10 to 40 years, a life support system centered on plants could provide most of
the resources necessary for mission success and independent sustainability.
9.4 Genomics and space exploration
The field of plant gravitational and space biology has started to utilize genetic and ge-
nomic technology to understand and manipulate the basic mechanisms of plant response
and adaptation to space conditions (Lomax et al. 2003). Transgenic Arabidopsis thaliana
seedlings flown for a short period on the Space Shuttle were used to study unique space
stress conditions (Paul et al. 2001), which in many ways were found to be similar to hy-
poxic stress. In a later report, genome-wide patterns of expression in space-flown
Arabidopsisshowed similarities to heat shock (Paul et al. 2005). However, no discernable
differences in gene expression were detectable in 23-day-old wheat seedlings grown on
the International Space Station when compared with the ground control plants (Stutte et
al. 2006), suggesting that many of the stress responses linked to space flight may be more
related to specific growth conditions rather than being an inherent component of the
space environment.
In ground-based studies, whole genome microarrays have been used to monitor global