Extraterrestrial Civilizations - Isaac Asimov [38]
There might be four worlds, then, in the outer Solar system, that could be far richer in life than Earth.
Yet life on these outer planets would be ocean life, for planets that are largely made up of volatiles with a preponderance of hydrogen must be purely liquid. There is no way in which we can expect continents or even islands.
The life forms on the outer planets would, therefore, be very likely to be streamlined for getting rapidly through a medium more viscous than Earthly air and would, in consequence, be very apt to lack manipulative organs.
And even if they could manipulate the environment, could they develop the use of a convenient form of inanimate energy equivalent to our fire? (To be sure, there is no free oxygen on a planet like Jupiter, but there is free hydrogen, and oxygen-rich compounds might burn in a hydrogen atmosphere.)
Somehow, it seems rather likely that if life developed on the giant planets and evolved to the point of intelligence, it would be the intelligence of the dolphin rather than that of the human being. It would be an intelligence that might lead to a better way of life, but it would not involve the building of a technology based on ever more elaborate and sophisticated tools, with which the intelligent creature might directly manipulate the environment more and more subtly.
This would also be true of life developing, against the odds, in a possible water layer beneath the surface crust of Ganymede or Callisto.
In other words, there might be life on Jupiter and the other giant planets, even intelligent life—but it doesn’t seem likely that there would be technological civilizations in our sense.
* Substances with molecules made up of carbon and hydrogen atoms only. Methane is an example.
CHAPTER 5
The Stars
SUBSTARS
Having gone rather exhaustively through the Solar system, it would appear that although there may be life on several worlds other than Earth, even conceivably intelligent life, the chances are not high. Furthermore, the chances would seem to be virtually zero that a technological civilization exists, or could exist, anywhere in the Solar system but on Earth.
Nevertheless, the Solar system is by no means the entire Universe. Let us look elsewhere.
We might imagine life in open space in the form of concentrations of energy fields, or as animated clouds of dust and gas, but there is no hint of evidence that such a thing is possible. Until such evidence is forthcoming (and naturally the scientific mind is not closed to the possibility), we must assume that life is to be found only in association with solid worlds at temperatures less than those of the stars.
The only cool, solid worlds we know are the planetary and subplanetary bodies that circle our Sun, but we cannot assume from this that all such bodies in the Universe must be associated with stars.* There may be clouds of dust and gas of considerably smaller mass than that from which our Solar system originated, and these may have ended by condensing into bodies much smaller than the Sun. If the bodies are sufficiently smaller than the Sun, say with only 1/50 the mass or less, they would end by being insufficiently massive to ignite into nuclear fire. The surfaces of such bodies would remain cool and they would resemble planets in their properties, except that they would follow independent motions through space and would not be circling a star.
All our experience teaches us that of any given type of astronomical body, the number increases as the size decreases. There are a greater number of small stars than of large ones, a greater number of small planets than large ones, a greater number of small satellites than large ones, and so on. Might we argue from that, that these substars, too small to ignite, are far greater in number than those similar bodies that are massive enough to ignite? At least one important astronomer, the American Harlow Shapley (1885–1972), has very strongly advanced the likelihood of the existence of such bodies.