Richard A. Proctor

“ Even those who have denied that Jupiter can be the abode of life, and have formed altogether unfavorable ideas of his condition, have pictured him nevertheless as the scene of continual calm, though the calm is, according to their view, the calm of gloom and desolation. They recognize in Jupiter an eternal winter rather than a perpetual spring. ”

“ It is not far from the truth to say that Jupiter's dimensions exceed the earth's in very nearly the same degree that those of the sun exceed Jupiter's. But his mass, though gigantic compared with the earth's, does not altogether correspond to his bulk, for it exceeds the mass of the earth only three hundred times. So that, if the disk our astronomers see and measure actually represents the true globe of the planet, his substance must be, on the average, much less dense than that of the earth. ”

“ And when some feature in a belt is seen to change slowly in figure—or, rather, when at the end of a certain time it is found to have so changed, for no eye can follow such changes as they proceed—we are not prepared to recognize in the process the evidence of disturbances compared with which the fiercest hurricanes that have ever raged on earth are as mere summer zephyrs. ”

“ We cannot get rid of this difficulty by a mere reference to the planet's rapid rotation, unless we are prepared to show how this rotation is to act in forcing the cloud-masses to become true belts. The whole substance of Jupiter and his whole atmosphere must take part in his rotation, and to suppose that aqueous vapor raised from his oceans would be left behind in the upper air, like the steam from a railway-engine, is to make a mistake resembling that which caused Tycho Brahe to deny the rotation of the earth, because bodies projected into the air are not left behind by the rotating earth. ”

“ During the year 1860, a rift in one of the Jovian cloud-belts behaved in such a way as to demonstrate the startling fact that a hurricane was raging over an extent of Jovian territory equalling the whole surface of our earth, at a rate of fully 150 miles per hour. It is not too much to say that a hurricane of like velocity on our earth would destroy every building in the territory over which it raged, would uproot the mightiest forest-trees, and would cause in fact universal desolation. At sea no ship that man ever made could withstand the fury of such a storm for a single minute. ”

“ So viewed, they could not be regarded as orbs fit for the support of living creatures. Yet, as each of them is the centre of a scheme of dependent worlds, of dimensions large enough to supply room for many millions of living creatures, we should not merely find a raison d'être for the outer planet's, but we should be far better able to explain their purpose in the scheme of creation than on any theory hitherto put forward respecting them. Jupiter as an abode of life is a source of wonder and perplexity, and his satellites seem scarcely to serve any useful purpose. ”

“ Our moon is by no means a minute body by comparison with the earth, and compared with Mars or Mercury she may be regarded as having very respectable dimensions. We may, indeed, look upon the moon as a fifth member of the inner family of planets—a member inferior to the rest, doubtless, but still not so far inferior to Mercury as Mercury is inferior to the earth. In the case of the outer planets, however, and especially in Jupiter's case, moons hold an utterly subordinate position. ”

“ If Jupiter showed no belts and shone with a pure white color, we could explain it at once by simply regarding Jupiter as wholly cloud-covered or snow-covered (for snow and cloud shine with nearly equal lustre when similarly illuminated) . But the great dark belts which occupy so large a proportion of the planet's disk altogether negative this supposition. We seem compelled to believe that some considerable portion of the planet's lustre is inherent. ”

“ And, after all, let us remember that the theory that Jupiter is an intensely heated globe—a theory to which we have been led by the consideration of many observed facts, and which in its turn suggests very satisfactory explanations of other observed facts—would merely show that, as Jupiter and Saturn hold an intermediate position between the sun and the minor planets in respect to size, so those giant orbs hold a corresponding position in respect of inherent heat. ”

“ We must, in the first place, dispossess ourselves of the notion, not uncommonly entertained, that Jupiter is one of a family of orbs, nearly equal in dignity and importance, and comprising the Earth and Venus, Mars and Mercury, among its members. ”

“ In winter, clouds are more common, and the air seems moister; yet, in reality, the quantity of aqueous, vapor is reduced. Now, it cannot but be regarded as a remarkable circumstance that, though the sun supplies Jupiter with only one twenty seventh part of the heat which we receive, there should yet be raised from the oceans of Jupiter such masses of clouds as to form veritable zones; and that, moreover, above these clouds there should be so large a quantity of invisible aqueous vapor that the spectroscopist can recognize the bands of this vapor in the planet's spectrum. ”

“ Setting aside the enormous activity of which the mere existence of the belts affords evidence, and even regarding such phenomena as the formation or a disappearance of a new belt in two or three hours as merely indicative of heavy rainfalls or of the condensation of large masses of invisible aqueous vapor into clouds—there have been signs, on more occasions than one, of Jovian hurricanes blowing persistently for several weeks together at a rate compared with which the velocity of our fiercest tornadoes seems utterly insignificant. ”

“ We regard Sirius as a sun, though in his spectrum the lines of hydrogen are abnormally strong; and, passing over the class of stars more closely resembling our sun, we regard as a true star the orange orb, Betelgeux, though the lines of hydrogen are wanting in its spectrum; nor do we reject from among the suns those stars which, like Gamma of Cassiopeia, show the lines of hydrogen bright upon a fainter rainbow-tinted spectrum. ”

“ There is yet another order of stars—those whose spectrum presents bright bands with faintly lustrous internals, which, again, we regard as true suns, though they differ doubtless notably from our own. But we have been in the habit of regarding all the star cloudlets, whether consisting of multitudinous stars, like the clusters, or of luminous star-mist, as differing toto coelo from the sun and from all his fellow-stars. The clusters, indeed, save a spectrum resembling the sun's, and we regard them as different only because of their clustering condition. ”

“ The alternation of day and night, which is one of the most potent of all the circumstances affecting the earth's meteorological condition, appears to have no effect whatever on the condition of Jupiter's atmosphere! ”

“ The strange problem presented by the rings, which naturally conceal the sun from immense regions of the planet for years together in the very heart of the winter of those regions, is satisfactorily solved when the Saturnian satellites are regarded as the abodes of life, and Saturn himself as the source of a considerable proportion of their heat-supply. We do not say that, in thus exhibiting the Jovian and Saturnian systems in a manner which accords with our ideas respecting the laws of life in the universe, we have given irrefragable testimony in favor of our theory. ”

“ Aqueous vapor in the atmosphere, whether its presence is rendered sensible to the sight or not, implies the action of heat. Other things being equal, the greater the heat the greater the quantity of watery vapor in the air. In the summer, for instance—though many imagine the contrary—there is much more of such vapor in the air than there is in winter, the greater heat of the air enabling it to keep a greater quantity of the vapor in the invisible form. ”

“ Bond supposed, but the planet yet shines three times as brightly as a globe of equal size would shine, if similarly placed, but constituted like Mars, and four times as brightly as such a globe would shine if constituted like our moon. Jupiter shines, in fact, very nearly as brightly as though he were constituted like one of our terrestrial clouds! ”

“ It will be obvious that, if the real globe of Jupiter is thus intensely heated, a portion of the planet's light must be inherent. Therefore we might expect that the planet would shine somewhat more brightly than a globe of equal size and similarly placed, shining merely by reflecting the sun's light. Now, two series of good observations have been made upon the luminosity of Jupiter. ”

“ A theory of the evolution of the solar system, advocated by me during the last seven years, according to which the solar system had its origin in meteoric and cometic aggregation, requires that during the long ages through which the process of development continued there should be occasional outbursts of light and heat in moderate degree from the rest of the system, even to its outskirts. ”

“ Now, heat is the only form of force which could account for the formation of the enormous masses of cloud suspended in the atmosphere of Jupiter. And it seems difficult to conceive that the clouds could be maintained at a great height above the real surface of the planet, unless that surface were intensely hot—as hot perhaps as red-hot iron. If we supposed this to be the case, we should find at once an explanation of the ruddy aspect of the dark belts. ”

“ But the great interest of the study of Jupiter resides in the fact that, being the nearest of the outer family of planets, the aspect of his globe supplies the best available means of determining the condition of the giant orbs constituting that family.
The first feature which strikes us in the telescopic aspect of the planet is the presence of a series of belts, lying parallel to the planet's equator. Usually the equatorial regions are occupied by a broad, bright belt, of a creamy-white color, and bordered on the north and south by copper-colored belts. ”

“ Tyndall, that some quality in Jupiter's atmosphere may prevent the solar heat from escaping, and so cause the climate of the planet to be not very different from the earth's, yet the direct heat falling on the planet's oceans cannot be increased in this way nay, it must be rather diminished. It chances, indeed, that the very quality by which the earth's atmosphere retains the solar heat is unquestionably possessed by Jupiter's atmosphere. ”

“ Roughly speaking, the earth is 8,000 miles, the sun 840,000 miles, in diameter, and Jupiter, with his diameter of 82,000 miles, comes midway between these orbs. Now, the sun is a white heat, and the earth gives out only what is called obscure heat; and, if Jupiter's globe is at a red heat, he again comes midway between the sun and the earth. ”

“ A difference so great that a satellite appears as a bright point close by the planet's edge, and almost black near the middle of the disk, suggests that the light near the edge is not reënforced by the inherent luminosity of our theory, that luminosity adding only to the brightness of the central parts of the disk. ”

“ It appears to us that, when these remarkable changes are considered in combination with the circumstance that on a priori grounds we should expect the sun to have very little influence on the condition of the planet's atmosphere, the idea cannot but be suggested that the chief source of all this energy resides in the planet itself. ”

“ However, speculation apart, we have in the discovery just made a most important fact for our guidance—the fact, namely, that a body which to ordinary observation has been in all respects like the star in the Crown, and even under spectroscopic observation shone for a while with true stellar light, has dwindled into a nebula giving the spectrum which has heretofore been regarded as indicative of ordinary gaseity.—English Mechanic. ”

“ Now, the object seen as a faint blue star showed the same spectrum as these gaseous nebulæ, or rather as the very faintest of these nebulæ. For most of them show three bright lines, and one or two even show four bright lines; only the faintest shine with absolutely monochromatic or one-tint light. The star in Cygnus now shines like these faintest of the gaseous nebulæ—that is, with a light which, under spectroscopic analysis, presents only one bright line. ”

“ Can it reasonably be questioned that, this being the case, we must look for the origin of the cloud-zones in these planets themselves, and not in the solar orb, whose action must needs be largely influenced by the alternation of night and day and of the seasons? ”

“ He appears as a bleak and desolate dwelling-place, and they together supply him with scarcely a twentieth part of the light which we receive from our moon at full. But, regarding Jupiter as a miniature sun, not indeed possessing any large degree of inherent lustre, but emitting a considerable quantity of heat, we recognize in him the fitting ruler of a scheme of subordinate orbs, whose inhabitants would require the heat which he affords to eke out the small supply which they receive directly from the sun. ”

“ This unwillingness to accept startling ideas is not to be altogether reprehended, since it prevents the mind from forming rash and baseless speculations. Yet we must not suffer this mental habitude, excellent though it may be in its proper place, to interfere with the admission of conclusions which seem based on trustworthy evidence. ”

“ The star in the Crown had shown the bright lines of hydrogen, superposed upon a faint rainbow-tinted spectrum, which was understood to signify that around a real, though probably a small, sun, some outburst of glowing hydrogen had taken place, the chief part of the star's new light being due to this outburst. The same bright hydrogen lines were seen also in the case of the star in Cygnus. ”

“ It happens that we have a very delicate means of measuring the degree of Jupiter's luminosity, as compared with that of other orbs similarly placed. For his satellites pass across his face, and nothing can be easier than to observe whether they appear darker or brighter than his surface. ”