9 Plan(t)s for Space Exploration
Christopher S. Brown*, Heike Winter Sederoff, Eric Davies,
Robert J. Ferl, and Bratislav Stankovic1839.1 Introduction
Mankindwillexplore the solar system. Some of that exploration will be done robotically,
allowing vicarious human experience and study of extraterrestrial locations. However, the
U.S. space program’s plans are replete with strategies to enable the first-hand humanex-
ploration of space. With the human system such an essential part of the long-term plan,
technologies to keep humans alive and performing at full capacity in extraterrestrial en-
vironments must be developed.
To accomplish the long-term goal of a stable human presence on other planetary bod-
ies in the solar system, the development and integration of a dependable life support sys-
tem is critical. Continued shipment and re-supply of the essentials for human survival—
breathable air, clean water, and food—would be risky as well as prohibitively expensive.
They are risky in that the shipments would depend on an absolutely fail-proof launch,
transit, and landing system. They are expensive in that, with current technologies, the cost
to get 1 kg into low Earth orbit is about $10,000. That’s a $3,000 hamburger!
Therefore, success of the human expansion into the cosmos must coincide with the de-
velopment of a life support system that is capable of regenerating all the essentials for
survival. Such systems already exist—they are called plants. Using the primary processes
of photosynthesis (air revitalization and biomass production) and transpiration (water pu-
rification), plants have provided human beings with all the essentials for survival as well
as many of the nonessentials that make life interesting.
To date, developing the engineering and infrastructure to get us into space has resulted
in important advances in transport and propulsion systems. But this is not all that is needed
for the successful human exploration of space. As stated by astrophysicist Freeman Dyson:
“The chief problem for a manned mission [to space] is not getting there but learning how
to survive after arrival. Surviving and making a home away from Earth are problems of bi-
ology rather than engineering. Any affordable program of manned exploration must be cen-
tered in biology, and its time frame tied to the time frame of biotechnology; a hundred
years[...] is probably reasonable. To make human space travel cheap, we will need advanced
biotechnology in addition to advanced propulsion systems.” (Dyson 1999)The development of a plant-based, biologically regenerative life support system is
therefore critical to providing the fundamental needs of a human crew. However, to be
fully supportive in a potentially changing environment, such a system must also be capa-
ble of responding to the changing needs of the personnel onboard. Plants must be capa-
ble of quickly reprogramming their metabolism, physiology, and growth to keep the crew
*Corresponding author