chance of widespread intelligence is remote according to Simpson and Gould’s version of Darwinian theory but it is likely to be prevalent if Davies’ appeal to law-like complexity is correct.
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4
LIFE IN THE SOLAR SYSTEM
Terraforming and colonization
The world is nearly all parcelled out, and what there is left of it is being divided up, conquered, and colonized. To think of these stars that you see overhead at night, these vast worlds which we can never reach. I would annex the planets if I could.
(Cecil Rhodes, Last Will and Testament, 1902)
Introduction
This chapter evaluates the search for life in the solar system, assessing the planets and their respective satellites, the asteroids and comets, as potential sites for life. Proposals for terraforming potentially habitable sites are assessed as well as the more ambitious proposals for the eventual colonization of space.
Life in the solar system
Assumptions that extraterrestrial forms of life could exist on other sites within the solar system provided a rationale for the elaborate and extremely expensive decontamination programmes to which returning astronauts were subjected in the 1960s. It is hard to imagine a lifeless planet. On Earth life exists in almost every nook and cranny. A puddle left after rainfall will very soon be teeming with countless forms of life. In deserts, at the bottoms of oceans, deep beneath the Earth’s crust, the phenomenon of life is ever present. But it is only recently that terrestrial scientists have possessed the equipment for the detection of planetary life. It is nevertheless important to maintain the distinction between conditions which are considered necessary for the emergence of life and conditions where life could survive and develop if generated elsewhere.
Broadly speaking, the solar system can be regarded as a potentially habitable zone. As yet, there are no uncontestable signs that life has been generated on other sites than Earth – and this is not absolutely certain, as life may have been generated elsewhere – but several extraterrestrial sites could plausibly be said to be capable of sustaining life. Although as a general rule planets or satellites should be in a relatively stable thermal zone, the possibility of tidal motion and
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