York University, Toronto, Canada
The latter devices cannot be inhabited indefinitely; for lengthy stays the crews sooner or later become dependent on resupply missions from Earth. Recently, the President of the United States called for the establishment of bases for astronauts on the moon and Mars. The first human outposts in space will, of necessity, be of the second kind, even though some local resources may be exploited by their occupants.
Human settlements on other planets can
become fully and permanently independent of Earth only of these
distant environments are transformed to provide Earth-like living
conditions and a local agriculture. The realistic possibilities for
this latter type of planetary engineering, carried out on a global
scale, are assessed briefly in this essay.
We are exotic products of a planetary
engine originally set in motion, and continuously fuelled, by energy
from the sun.
Though presently barren, Mars, nonetheless, is a biocompatible planet. Its unalterable physical characteristics (e.g. size, density, gravity, orbit, rotation rate, incident sunlight) and its possible chemical resources are remarkably consistent with life. Indeed, it was the hope that organisms might be found on Mars that made life-detection the top priority for NASA’s Viking missions in 1976.
However, all of the ingenious biological
experiments carried out by the two robotic landers gave negative
This thin atmosphere consists of 95% carbon dioxide and 3% nitrogen, with only trace amounts of water vapour, oxygen and other gases. There is no protective ozone layer to shield the planet from the ultraviolet radiation emitted by the sun. Most surprising was the absence from the soil of any detectable organic molecules, the building blocks of life.
Even though such materials arrive on
Mars in meteorites, they are subsequently destroyed, at least on the
surface of the planet. Thus, any organisms which might arrive there
unprotected today would be freeze-dried, chemically degraded, and
soon reduced to dust. It would not be possible to ‘seed’ Mars just
by sprinkling bacteria over its surface.
A major uncertainty in these discussions
is whether there remains on Mars today adequate amounts of carbon
dioxide, water and nitrogen to allow such a planetary-scale
transformation. If most of Mars’ original endowment of these
materials has been lost to space, then the regeneration of a
habitable state would be impossible.
This atmosphere would be warm and moist, and water would flow again in the dried up river beds. The average temperature at the surface would rise to about 15 degrees Celsius and the atmospheric pressure would be roughly twice that on Earth. Appropriately selected, or genetically engineered, anaerobic microorganisms, and eventually some plants, could grow under these conditions.
If future exploration reveals that the
necessary volatiles are indeed available then a new home for life
might someday be created on our sister planet.
Obviously, this would not provide an environment in which animals or humans could survive outdoors. All oxygen-dependent organisms transported to Mars would have to remain enclosed in life-support modules or appropriate protective gear. The word ‘terraformation’ is used to describe the formation of specifically Earth-like, aerobic conditions on planets. Such a salubrious environment is only one of many possible long-term and not necessarily inevitable, outcomes of ecopoiesis.
If we consider the spontaneous development of Earth’s biosphere as a model for what might be achieved by design on Mars, terraformation would have to be initiated subsequently to ecopoiesis. If we restrict our speculations to plausible, near-term technologies, the time periods required to carry out ecopoiesis and terraformation on Mars are very different. If suitable volatile inventories exist, the thick, warm atmosphere described above might be generated in as little as 200 years.
However approximately 100,000 years
would be required if an oxygen atmosphere was to be produced as
efficiently as it was on Earth, that is, by microbial and green
plant photosynthesis. However, it remains possible that presently
unimagined, futuristic technologies could be developed to shorten
these time estimates considerably.
For example, do humans have any right to
‘play God’ on another planet?
However, in an amazing biotic diaspora, microrganisms, followed by plants and animals, migrated from marine to fresh water environments and then onto the initially barren land. None of this would have been possible were it not for the evolutionary development, by living cells, of the ‘technology’ of photosynthesis. Essentially all of the free oxygen (and the resulting ozone shield) in Earth’s atmosphere was, and is, generated by photosynthesis.
Even though oxygen is poisonous to most
anaerobic organisms, its accumulation in the atmosphere created the
conditions necessary for the flowering of aerobic life as we know it
Rather, it has been the amazingly rapid
and efficient processes of social and technological evolution which
have facilitated the propagation of our species, across every
continent, and most recently into space.
Against this background it is not just an idle dream to imagine that people might yet "slip the surly bonds of Earth" to pioneer new habitats in the sky. Further exploration of Mars may well reveal that ecopoiesis is feasible on that planet. Such a discovery would provide future generations with a tremendous challenge in life and an exhilarating vision of the role of humankind as a participant in creation.
Perhaps however, there are also deep
psychological and biological reasons for seeking to enliven Mars:
such a vast enterprise would surely be consistent with the
Promethean myths of many cultural traditions and the proliferative
imperative that animates life itself.