[All Rights Reserved.] The Oceans and Clouds of Other Planets.

Te Aroha News, Volume VII, Issue 415, 30 October 1889, Page 3

[All Rights Reserved.] The Oceans and Clouds of Other Planets.

BY SIR ROBERT BALL.

Mars. It is, therefore, reasonable to believe that we actually find on the planeb the presence of ice and snow, nnd this confirms us in the belief that those dark features on the globe which our charts of Mara speak of as seas or oceans are proporly 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 the surface of our earth was like by a scouting conducted with even the best of telescopes from Mars. The atmosphere surrounding that planeb is of a less dense description than that in which we are enveloped^ In fact, it requires careful observations to prove that Mars has any atmosphere at all, but the existence of some 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 are of a somewhat delicate nature. The discoveries, about this planet are, however, specially interesting to us, because they show us so manypoints of resemblance between Mars and our earth, in fact of all the globes which the heavens contain there is no one, so far as we know, which seems so like our earth as does this ruddy neighbour. The colour 'which gives the planet its well-known appearance is produced by the large region whjch, in contrast to Mars' oceans, are spoken of as continents. If clouds are comparatively an important feature on Mars, they assume the most extraordinary impor,tance oh 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 ofch6c 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, these belts on Jupiter are not fixed features of this 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, the greater part of the surface of the planet is more or less 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 the 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 Jupiter is enormously swollen by these mighty banks dt clouds which so closely encase him. Careful measurements having been made, it has been shown that Jupiter is 1,200 times biyger 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 meana of weighing a great planet as well as of measuring it. How this weighing is to be effected I shall not here pause 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 .] upiter is about 300 times as heavy as the earth. This gives us indeed an impressive idea of the magnificence of the mightiest of the planets. Were a gigantic weighing scales constructed, and were Jupiter to be placed in one pair of that scales, 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 times as big as another then it will be ten times as heavy. The lightness of Jupiter in comparison to his size is really the point that merits our astonishment. He is indeed nofc. as very much heavier than a globe of water the same size would be, while our earth. i 3 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 eive him a bigness altogether out of proportion to his mass. Therefore as Mars gave 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 leani 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.