CHAPTER XVIII.

SATURN.

The system of Jupiter is a simple system compared with that of Saturn, next in order. For whereas Jupiter has only five moons, Saturn has eight, and, in addition to these, he has three wonderful rings. Neither rings nor moons can be seen without a telescope, on account of Saturn’s great distance from us--more than three thousand times the distance of the moon, or upwards of eight hundred millions of miles. Saturn’s mean distance from the sun is eight hundred and seventy-six million seven hundred and sixty-seven thousand miles.

Saturn does not equal his mighty brother Jupiter in size, though he comes near enough in this respect to be called often his “twin”--just as that small pair of worlds, Venus and Earth, are called “twins.” While Jupiter is equal in size to over one thousand two hundred earths, Saturn is equal to about seven hundred earths. And while Jupiter is equal in weight to three hundred earths, Saturn is only equal in weight to ninety earths. He appears to be made of very light materials--not more than three-quarters as dense as water. This would show the present state of Saturn to be very different from the present state of the earth. We are under the same uncertainty in speaking of Saturn as in speaking of Jupiter. Like Jupiter, Saturn is covered with dense masses of varying clouds, occasionally opening and allowing the astronomer peeps into lower cloud-levels; but rarely or never permitting the actual body of the planet to be seen.

The same perplexities also come in here, to be answered much in the same manner. We should certainly expect that in a vast globe like Saturn the strong force of attraction would bind the whole into a dense solid mass; instead of which, Saturn is about the least solid of all the planets. He seems to be made up of a light, watery substance, surrounded by vapor.

[Illustration: SATURN AND THE EARTH--COMPARATIVE SIZE.]

One explanation can be offered. What if the globe of Saturn be still in a red-hot, molten state, keeping such water as would otherwise lie in oceans on his surface, floating aloft in masses of steam, the outer parts of which condense into clouds?

No one supposes that Jupiter and Saturn are in the same condition of fierce and tempestuous heat as the sun. They may have been so once, but they must now have cooled down very many stages from that condition. Though no longer, however, a mass of far-reaching flames and fiery cyclones, the body of each may have only so far cooled as to have reached a stage of glowing molten red-heat, keeping all water in the form of vapor, and sending up strong rushes of burning air to cause the hurricanes which sweep to and fro the vast cloud-masses overhead.

And if this be the case, then, with Saturn as with Jupiter, comes the question, Can Saturn be inhabited? And if--though we may not say it is impossible, yet we feel it to be utterly unlikely--then again follows the question, What if Saturn’s _moons_ are inhabited?

Telescopic observations tempt us to believe that there is on this planet a quantity of heat greater than that which results from its distance from the sun; for the day-star as seen from Saturn is, as we have said, ninety times smaller in surface, and its heat and light are reduced in the same proportion. Water could only exist in the solid state of ice, and the vapor of water could not be produced so as to form clouds similar to ours. Now, meteorological variations are observed similar to those which we have noticed on Jupiter, but less intense. Facts, then, combine with theory to show us that the world of Saturn is at a temperature at least as high as ours, if not higher.

But the strangest feature of the Saturnian calendar is, unquestionably, its being complicated, not only with the fabulous number of 25,060 days in a year, but, further, with eight different kinds of months, of which the length varies from 22 hours to 79 days--that is to say, from about two Saturnian days to 167. It is as if we had here _eight moons revolving in eight different periods_.

The inhabitants of such a world must assuredly differ strangely from us from all points of view. The specific lightness of the Saturnian substances and the density of the atmosphere will have conducted the vital organization in an extra-terrestrial direction, and the manifestations of life will be produced and developed under unimaginable forms. To suppose that there is nothing fixed, that the planet itself is but a skeleton, that the surface is liquid, that the living beings are gelatinous--in a word, that all is unstable--would be to surpass the limits of scientific induction.

The diameter of the largest moon is about half the diameter of the earth, or much larger than Mercury. The four inner satellites are all nearer to Saturn than our moon to us, though the most distant of the eight is ten times as far away. The inner moon takes less than twenty-three hours to travel round Saturn, and the outer one over seventy-nine days.

A great many charming descriptions have been worked up, with Saturn as with Jupiter, respecting the magnificent appearance of the eight radiant moons, joined to the glorious shining of the rings, as quite making up for the diminished light and heat of the sun. But here again comes in the doubt, whether really it is the moons who make up to Saturn for lack of light, or whether it is Saturn who makes up to the moons for lack of light.

Certainly, Saturn’s cloudy covering would a little interfere with observations of the moons by any inhabitants of the solid body within--supposing there be any solid body at all. And though it sounds very wonderful to have eight moons instead of one moon, yet all the eight together give Saturn only a very small part of the light which we receive from our one full moon--so much more dimly does the sun light them up at that enormous distance.

The same thing has been noticed with Saturn as with Jupiter--that he seems to shine more brightly than is to be expected in his position, from mere reflection of the sun’s rays. A glowing body within, sending a certain amount of added light through or between the masses of clouds, would explain away this difficulty.

One more possible proof of Saturn’s half-liquid state is to be found in his occasional very odd changes of shape. Astronomers have been startled by a peculiar bulging out on one side, taking off from his roundness, and giving a square-shouldered aspect. We may not say it is quite impossible that a solid globe should undergo such tremendous upheavals and outbursts as to raise a great portion of its surface five or six hundred miles above the usual level--the change being visible at a distance of eight hundred millions of miles. But it would be easier to understand the possibility of such an event, in the case of a liquid, seething mass, than in the case of a solid ball.

On the other hand this alteration of outline may be caused simply by a great upheaval not of the planet’s surface, but of the overhanging layers of clouds. Some such changes, only much slighter, have been remarked in Jupiter.

And now as to the rings. Nothing like them is to be seen elsewhere in the Solar System. They are believed to be three in number; though some would divide them into more than three. Passing completely round the whole body of Saturn, they rise, one beyond another, to a height of many thousands of miles.

The inner edge of the inner ring--an edge perhaps one hundred miles in thickness--is more than ten thousand miles from the surface of Saturn or more strictly speaking, from the outer surface of Saturn’s cloudy envelope. A man standing exactly on the equator and looking up, even if no clouds came between, would scarcely be able to see such a slender dark line at such a height.

This dark, transparent ring, described sometimes as dusky, sometimes as richly purple, rises upwards to a height or breadth of nine thousand miles. Closely following it is a ring more brilliant than Saturn himself, over eighteen thousand miles in breadth. When astronomers talk of the “breadth” of these rings, it must be understood that they mean the width of the band measured _upwards_, in a direction away from the planet.

Beyond the broad, bright ring is a gap of about one thousand seven hundred miles. Then follows the third ring, ten thousand miles in breadth; its outermost edge being at a height of more than forty-eight thousand miles from Saturn. The color of the third ring is grayish, much like the gray markings often seen on Saturn.

What would not be our admiration, our astonishment, our stupor perhaps, if it were granted us to be transported there alive, and, among all these extra-terrestrial spectacles, to contemplate the strange aspect of the rings, which stretch across the sky like a bridge suspended in the heights of the firmament! Suppose we lived on the Saturnian equator itself, these rings would appear to us as a thin line drawn across the sky above our heads, and passing exactly through the zenith, rising from the east and increasing in width, then descending to the west and diminishing according to perspective. Only there have we the rings precisely in the zenith. The traveler who journeys from the equator towards either pole leaves the plane of the rings, and these sink imperceptibly, at the same time that the two extremities cease to appear diametrically opposite, and by degrees approach each other. What an amazing effect would be produced by this gigantic arch, which springs from the horizon and spans the sky! The celestial arch diminishes in height as we approach the pole. When we reach the sixty-third degree of latitude the summit of the arch has descended to the level of our horizon and the marvelous system disappears from the sky; so that the inhabitants of those regions know nothing of it, and find themselves in a less favorable position to study their own world than we, who are nearly 800,000,000 miles distant.

During one-half of the Saturnian year the rings afford an admirable moonlight on one hemisphere of the planet, and during the other half they illuminate the other hemisphere; but there is always a half-year without “ringlight,” since the sun illuminates but one face at a time. Notwithstanding their volume and number, the satellites do not give as much nocturnal light as might be supposed; for they receive, on an equal surface, only the ninetieth part of the solar light which our moon receives. All the Saturnian satellites which can be at the same time above the horizon and as near as possible to the full phase do not afford more than the hundredth part of our lunar light. But the result may be nearly the same, for the optic nerve of the Saturnians may be ninety times more sensitive than ours.

But there are further strange features in this system. The rings are so wide that their shadow extends over the greater part of the mean latitudes. During fifteen years the sun is to the south of the rings, and for fifteen years it is to the north. The countries of Saturn’s world which have the latitude of Paris endure this shadow for more than five years. At the equator the eclipse is shorter, and is only renewed every fifteen years; but there are every night, so to say, eclipses of the Saturnian moons by the rings and by themselves. In the circumpolar regions the day-star is never eclipsed by the rings; but the satellites revolve in a spiral, describing fantastic rounds, and the sun himself disappears at the pole during a long night of fifteen years.

At one time it was supposed that the rings were solid, but they are now believed to consist of countless myriads of meteorites, each whirling in its own appointed pathway round the monster planet.

[Illustration: IDEAL VIEW OF SATURN’S RINGS AND SATELLITES FROM THE PLANET.]

As already said--leaving out of the question the cloudy atmosphere--a man standing on the equator would see nothing of the rings. A man standing at the north pole or the south pole of Saturn could see nothing either, since the rings would all lie below his horizon. But if he traveled southward from the north pole, or northward from the south pole, towards the equator, he would in time see the ringed arch appearing above the horizon, rising higher and growing wider with every mile of his journey; and when he was in a position to view the whole broad expanse, the transparent half-dark belt below, the wide radiant band rising upwards over that, and the grayish border surmounting all, he would truly have a magnificent spectacle before him.

This magnificent spectacle is, however, by no means always visible, even from those parts of Saturn where alone it ever can be seen. The rings shine merely by reflected sunlight. Necessarily, therefore, while the sunbeams make one side bright the other side is dark; and not only this, but the rings throw broad and heavy shadows upon Saturn in the direction away from the sunlight.

In the daytime they probably give out a faint shining, something like our own moon when seen in sunlight. During the summer nights they shine, no doubt, very beautifully. During the winter nights it so happens that their bright side is turned away; and not only that, but during the winter days the rings, while giving no light themselves to the wintry hemisphere of Saturn, completely hide the sun.

When it is remembered that Saturn’s winter--that is, the winter of each hemisphere in turn--lasts during fifteen of our years; and when we hear of total eclipses of the sun lasting unbroken through eight years of such a winter, with not even bright rings to make up for his absence, we can not think of Saturn as a tempting residence. The sun gives Saturn at his best only about one-ninetieth of the heat and light that he gives to our earth; but to be deprived of even that little for eight years at a time, does indeed sound somewhat melancholy.

Looking now at the other side of the question, the possible inhabitants of the moons, especially those near at hand, would have splendid views of Saturn and his rings in all their varying phases. For Saturn is a beautiful globe, wrapped in his changeful envelope of clouds, which, seen through a telescope, are lit up often with rainbow tints of blue and gold; a creamy white belt lying usually on the equator; while around extend the purple and shining and gray rings, sometimes rivaling in bright colors Saturn himself.

We are compelled to assume that the continuous appearance of the rings is not due to real continuity of substance, but that they are composed of flights of disconnected satellites, so small and so closely packed that, at the immense distance to which Saturn is removed, they appear to form a continuous mass. There are analogous instances in the Solar System. In the zone of asteroids we have an undoubted instance of a flight of disconnected bodies traveling in a ring about a central attracting mass. The existence of zones of meteorites traveling around the sun has long been accepted as the only probable explanation of the periodic returns of meteoric showers. Again, the singular phenomenon called the Zodiacal Light is, in all probability, caused by a ring of minute cosmical bodies surrounding the sun. In the Milky Way and in the ring-nebulæ we have other illustrations of similar arrangements in nature, belonging, however, to orders immeasurably vaster than any within the Solar System.

The moons of Saturn do not, like those of Jupiter, travel in one plane.