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The Oceans and Clouds of Other Planets., Issue 8048, 26 October 1889, Supplement
The Oceans and Clouds of Other Planets.
[Bv Sir Koeebt Ball.]
Our earth has a number of brothers and sisters, for bo we may describe our fellow planets which revolve around the sun as we do. These other planets are also guided and held in their ever circling way by the attraction of the sun, while they are also illuminated by the light which he pours forth with such liberality, and warmed with the rays of heat which he sends them. The sun does not indeed confer these benefits in an equal degree on all the members of his family, those which are nearer to him get much, perhaps too much according to our notions of his heat, while those like Uranus or Neptune which lie on the outskirts of the system get little, perhaps too little, of thoße Particular beneßts which he dispenses, his world of ours thus a rather intermediate position. Our bodies would have to be considerably modified if we are to
find a congenial residence either so near the sun as Mercurjr ok t6 Tar from him as Neptune. As v/c live on this earth in the tern-, perato rogions and suffer neither from the ' fearful heat at the Equator nor from the horrors of the frozen polo, Jo, tco, does our entire world enjiby what we may describe as a temperate situation in the arrangement of the b'odies belonging to the solar system. in other respects, too, our position is an intermediate one. Thero arc some planets, ! such as Mars and Mercury, which are Very' much smaller than our earth. There are ; other planets, such as Jupiter and Saturn, which mb enormously greater than the earth ; and there la Venus, our beautiful neighbor, which is almost exactly the same size that we are. Considering that this earth may be taken as an average specimen cf the worlds which form the sun's family, it is natural to inquire how far the other planets may be eoustituted in the same way that we arc, Most of the questions which we would like to ask on t!u* head are such as, unhappily, canw.-fc lie answered. Especially wouM v,S 'like to know whether the other p'aiiets are inhabited, but on this our grrrUest telescopes can give us no information whatever, and we can only form the vainest surmises. All we can expect to see on the neighboring planets must be features of immense dimensions. It would, for example, lie utterly impossible for us to recognise town.*, even if such things as towns existed, though it might still be possible to discern the broader outlines of extensive continents or mighty oceans, We could also observe the clouds, if clouds existed, around a neighboring planet, because owing to their '-stent unci to their position on the ou Icicle they would be comparatively easy to ws, while the incessant changes of the clouds would render them an attractive feature to the observer.
Wo have accordingly in this little paper decided to fifty what we can with respect to the clouds and oceans which arc to be met with on some of the other planets. Even here, however, we mint be content with a knowledge which is much more scanty that: an intelligent curiosity would desire. In many of the planets '..n can see little or nothing of this kind th<w cm be certainly made out, while even on those which wo can see best it is only the very broadest and most striking features that can bt: delineated. Of Venus, unhappily, we can sec nothing or next to nothing which would give us any information as to the presence or the absence of oceans and clouds from this planet. The loveliness ol the evening star is duo to the brilliancy of the sunbeams in which she is decked ; but this very brilliancy is inconvenient in the telescope, where it merely appears as a glare, which renders all details invisible. Beyond a few ill-defined and inconspicuous works, nothing has ever been seen on this body which is of any interest for our present purpose. The ease is widely different when we look nt our earth's neighbor on the other side, the ruddy planet Mars.
Under certain circumstances Mars and the earth draw sufficiently close together to enable us to inspect him with close attention, and when we do so we find unequivocal evidence of the existence of clouds over his nirfae-.:, ?.nrl of Wore permanent workings on that surface which we have good reason to believe are of tho nature of oceans. Maps have been carefully drawn, and even globes have been constructed in which these features of the planet have been carefully depicted ; indeed, astronomers have made a speei.i! geography of tho planet, in which the different objects are appropriately named and duly described. Thus we have tl,e n-iine of Delia line Ocean given to one imvwtant tract of a dari: cokr, which it is diliie.nlt ri'it to believe is really an ocean of water. Then there are bays and straits and lake-; and, strangest of all, long dark tviuais connecting the different seas, many of which seem to undergo remarkable changes. Indeed, a well-known astronomer not Ion:; ago astonished ths World by showing that many of theuo Cana.l3 were really double—that they consisted of two long dark canals side by side, It would be going too far to assert that we are certain that those objects are really of the nature which the names they have received would imply. But there is an excellent reason for believing that water iii to be found on Mars which possesses the co'.dition of ice and snow wbenth-i temperature is suitable. In fact, one of the most, interesting telescopic features about this planet is the presence of its remarkable arctic regions.
At the north polo of Mara there will be found at ei'Vtam seasons an accumulation of a white material, which increases audde- ' creases in accordance 1 , with the fluctviatiofiß 'of the seasons. As it gradually shrinks back to the pole in summer time it sometimes leaves white glistening pitches on the peaks of the lofty mountains. The south pole of the planet is also the centre about which a white mass increases and decreases in correspondence with the changes of the seasons produced by the revolutions of Mars around the Sun. There can be no doubt that if we were able to take a bird's-eye view of our own tarth free from the obstruction of the clouds, so that we could sec its north pole or its south pole in the same way that we sec tho two poles of Mars we 3hould find that the arctic and antarctie : regions each had a vast cap of ice and snow which would alter with the changes of the seasons and resemble in every respect those objects which we see on Mars. It is, therefore, reasonable to believe that we actually find on tho planet the presence of ice and snow, and this confirms us in tho belief that those dark features on the globe which our charts of Mars speak of as seas or oceans are properly so designated. We are able to see Mars better than an inhabitant of that planet would be able to see us, Indeed our atmosphere is so copious, and the clouds with which it is often charged are so numerous that it would be very difficult to obtain an adequate notion of what j tho surface of our earth was like by a scouting conducted with even the best of tolol scopes from Mars. The atmosphere surj rounding that planet is of a less dense description than that in which we are enveloped. In fact it requires careful i observations to prove that Mara has any atmosphere at all; but the existence of some I atmosphere there is undoubted, and clouds are occasionally seen floating in it. These clouds are, however, so slight that the observations which prove their existence arc of a somewhat delicate nature. The discoveries about this planet are, however, specially interesting to us, because they show us so many points of resemblance between Mars and our earth; in fact, of all the globes which the heavens contain there is not one, bo far as we know, which seems so like our earth as does this ruddy neighbor. The color which gives the planet its wellknown appearance is produced by the large region which, in contrast to Mars' oceans, [ are spoken of as continents, | If clouds are comparatively an important | feature on Mars, they assume the most | extraordinary importance on the next planet we have to speak about, and that is Jupiter. He is a gigantic body, by far the largest of all the planets—larger, indeed, than all the other planets put together. Viewed in the telescope, the surface of Jupiter is usually seen crossed by two belts—one above and one below his equator. You would produce something like it on any ordinary globe by making a broad belt on the Tropic of Cancer and another on the Tropic of Capricorn. Now, theso beltson Jupiterare notfixed features of his surface—they are constantly changing their aspect. Sometimes, indeed, they are hardly to be seen at all, and sometimes they widen their limits and become irregular at their edges; sometimes, indeed, tho greater part of the surface of the planet is more or leß3 covered over with similar markings. We see nothing on this great planet that resembles the oceans and the continents on Mars, nor have we any indications of the arctic regions on its surface. In fact, the longer we look at Jupiter the more we become convinced that the entire of this planet is swathed with a mighty volume of clouds so dense and so impenetrable that our most powerful telescopes have never yet been able to pierce through these clouds down to tho solid surface of the planet. Indeed we can hardly say whether this planet has any solid interior at all. There | is one object on it known as the great red spot, which for several years was more or less recognisable. This seemed to be some great volcano, or some other object from the interior, which was tall enough and large enough to make itself visible through the mighty covering of clouds which act as an effectual screen to hide all objects of lower prominence.
There is another very interesting way in which we can confirm the fact that Jnpiter is enormously swollen by these mighty bunks of clouds which so closely encase him. Careful measurements having been made it has been shown that Jupiter is 1,200 times bigger than our earth ; in other words that 1,200 globes each as large as this earth rolled together into one would only form a ball as big as this mighty planet. Astronomers also have the means of weighing a great planet as well as of measuring it. How this weighing is to be effected I shall not here pau*o to describe; suffice it to say that the little moons by which Jupiter is attended afford by their movements the means of answering the question, and the answer is a significant one, for we find that Jupiter is about 300 times as heavy ai the earth. Thiß gives us indeed an impressive idea of the magnificence of the mightiest of the planets. *>Vere a gigantic weighing scale constructed, and were Jupiter to be placed in it; then it would require 300 globes each as heavy as the earth to be placed in the others before the mighty .scale could turn. Yet, when we remember that Jupiter is 1,200 times as large as the earth, we may well feel surprised at learning that he is only 300 times as heavy. Were the constitution of the planet at all like that of our earth then the weights and the sizes should observe the same proportions, just as if one cannon ball be ten time 3 as big as another then it will be ten times as heavy. The lightness of Jnpiter in comparison to his size is really the point that merits our astonishment. He is indeed not very much heavier than a globe of water the same size would be, while our earth is five times as heavy as a globe of water equally large. The true explanation is that Jupiter is so swollen by these enormous masses of cloud which surround him as to give him a bigness altogether out of proportion to his mass. Therefore, as Mars gives us an illustration of the existence of oceans on other planets, so Jupiter provides us with a splendid example of a planet encompassed with clouds. Then we learn that two oceans and two clouds so characteristic of these our earth are not without their equivalents on some of the other worlds which abound through them.
The Oceans and Clouds of Other Planets., Issue 8048, 26 October 1889, Supplement
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