Other Worlds / Their Nature, Possibilities and Habitability in the Light of the Latest Discoveries

by Garrett Putman Serviss

In attempting to judge the habitability of a planet such as Venus we must first, as far as possible, generalize the conditions that govern life and restrict its boundaries.

On the earth we find animated existence confined to the surface of the crust of the globe, to the lower and denser strata of the atmosphere, and to the film of water that constitutes the oceans. It does not exist in the heart of the rocks forming the body of the planet nor in the void of space surrounding it outside the atmosphere. As the earth condensed from the original nebula, and cooled and solidified, a certain quantity of matter remained at its surface in the form of free gases and unstable compounds, and, within the narrow precincts where these things were, lying like a thin shell between the huge inert globe of permanently combined elements below, and the equally unchanging realm of the ether above, life, a phenomenon depending upon ceaseless changes, combinations and recombinations of chemical elements in unstable and temporary union, made its appearance, and there only we find it at the present time.

It is because air and water furnish the means for the continual transformations by which the bodies of animals and plants are built up and afterward disintegrated and dispersed, that we are compelled to regard their presence as prerequisites to the existence, on any planet, of life in any of the forms in which we are acquainted with it. But if we perceive that another world has an atmosphere, and that there is water vapor in its atmosphere—both of which conditions are fulfilled by Venus—and if we find that that world is bathed in the same sunshine that stimulates the living forces of our planet, even though its quantity or intensity may be different, then it would seem that we are justified in averring that the burden of proof rests upon those who would deny the capability of such a world to support inhabitants.

The generally accepted hypothesis of the origin of the solar system leads us to believe that Venus has experienced the same process of evolution as that which brought the earth into its present condition, and we may fairly argue that upon the rocky shell of Venus exists a region where chemical combinations and recombinations like those on the surface of the earth are taking place. It is surely not essential that the life-forming elements should exist in exactly the same states and proportions as upon the earth; it is enough if some of them are manifestly present. Even on the earth these things have undergone much variation in the course of geological history, coincidently with the development of various species of life. Just at present the earth appears to have reached a stage where everything contributes to the maintenance of a very high organization in both the animal and vegetable kingdoms.

So each planet that has attained the habitable stage may have a typical adjustment of temperature and atmospheric constitution, rendering life possible within certain limits peculiar to that planet, and to the special conditions prevailing there. Admitting, as there is reason for doing, that different planets may be at different stages of development in the geological and biological sense, we should, of course, not expect to find them inhabited by the same living species. And, since there is also reason to believe that no two planets upon arriving at the same stage of evolution as globes would possess identical gaseous surroundings, there would naturally be differences between their organic life forms notwithstanding the similarity of their common phase of development in other respects. Thus a departure from the terrestrial type in the envelope of gases covering a planet, instead of precluding life, would only tend to vary its manifestations.

After all, why should the intensity of the solar radiation upon Venus be regarded as inimical to life? The sunbeams awaken life.

It is not impossible that relative nearness to the sun may be an advantage to Venus from the biologic point of view. She gets less than one third as much heat as Mercury receives on the average, and she gets it with almost absolute uniformity. At aphelion Mercury is about two and four tenths times hotter than Venus; then it rushes sunward, and within forty-four days becomes six times hotter than Venus. In the meantime the temperature of the latter, while high as compared with the earth's, remains practically unchanged. Not only may Mercury's temperature reach the destructive point, and thus be too high for organic life, but Mercury gets nothing with either moderation or constancy. It is a world both of excessive heat and of violent contrasts of temperature. Venus, on the other hand, presents an unparalleled instance of invariableness and uniformity. She may well be called the favorite of the sun, and, through the advantages of her situation, may be stimulated by him to more intense vitality than falls to the lot of the earth.

It is open, at least to the writers of the interplanetary romances now so popular, to imagine that on Venus, life, while encompassed with the serenity that results from the circular form of her orbit, and the unchangeableness of her climates, is richer, warmer, more passionate, more exquisite in its forms and more fascinating in its experiences, keener of sense, capable of more delicious joys, than is possible to it amid the manifold inclemencies of the colder earth.

We have seen that there is excellent authority for saying that Venus's atmosphere is from one and a half to two times as dense and as extensive as ours. Here is an interesting suggestion of aerial possibilities for her inhabitants. If man could but fly, how would he take to himself wings and widen his horizons along with the birds! Give him an atmosphere the double in density of that which now envelopes him, take off a little of his weight, thereby increasing the ratio of his strength and activity, put into his nervous system a more puissant stimulus from the life-giving sun, and perchance he would fly.

Well, on Venus, apparently, these very conditions actually exist. How, then, do intellectual creatures in the world of Venus take wing when they choose? Upon what spectacle of fluttering pinions afloat in iridescent air, like a Raphael dream of heaven and its angels, might we not look down if we could get near enough to our brilliant evening star to behold the intimate splendors of its life?