THE SE AS AND SNOWS IN MARS.
THERE are, perhaps, no other scientific interests so absorbing as those which open glimpses to us of the possible conditions of life in the other worlds which man can never hope to pene- trate, except by the sense of vision. When, about ten years ago, Dr. Whewell exerted himself to persuade us that the stellar and planetary universe is a spiritual desert, with the sole exception of the little planetary oasis inhabited by man, his hypothesis was received, not so much with incredulity as with intellectual resent- ment. The interest which astronomy excites half consists in the pleasure of conceiving the great variety of intellectual conditions which the observed differences of situation would introduce into the life of a human emigrant. How the wealth of moons would affect the inhabitants of Jupiter, whether it has stimulated their scien- tific powers, supposing them to have scientific powers, in the same proportion in which one single moon has stimulated our own,—whether the four moons figure four times as much in Jovian poetry and mythology as one single moon in ours—what effect the frequent lunar eclipses have had on their astronomical progress,—what the consequence of the enormous weight which the great bulk of Jupiter gives to both inanimate and animate bodies, may be on Jovian architecture and Jovian gymnastics,— whether the very short days and nights, of less than five hours each, tend to intellectual activity or despair, to fast or slow life, haste or dawdling,— all these questions, unanswerable as they are, are part and parcel of the acute interest with which we investi- gate the Jovian astronomy. Who can help interesting himself profoundly in the same way about the Saturnian rings ? Do the inhabitants of the two rings (if any) communicate across the very inconsiderable distance of 1,790 miles? — a telegraph across it would not be so long as the Atlantic telegraph. Can the Ringers, as we may call them, get at the inhabitants of the ball—it is not so far from the interior ring as it is round the circumference of our own Earth—and what may be the ethnological relations of the Ring-races and the Saturnian globe-races? No doubt these are all to us insoluble questions, and yet the mere fact that we can and do put such questions to ourselves is the secret of half the intensity of interest with which we pursue the subject. Or again, going still farther away from the centre of our own situation in the Universe—what was the secret of the delight with which the existence of double and different-coloured suns moving round each other was first recognized? Surely it was the surprise to the imagi- nation of so new a situation as the (possible) inhabitants of any planet of one of these suns would occupy. They would some- times have, we argue, a blue day and a red day following each other, like our day and night,—the blue sun rising as the red sun- set. Sometimes they would have a partially white day, caused by the mingling of the two lights, with, perhaps, a blue early morning and a red afternoon ; and a double noon, as each sun separately comes to the meridian. All these complexities of outward influence would probably engender corresponding com- plexities of intellectual and moral culture, and the inhabitants of such worlds may be conceived with a literature and a science as far superior to our own as the variety of their physical influences is greater. And whatever new stellar fact astronomy discovers for us, the avidity with which we seize on it half depends on the assumption that there are minds like or superior to ours, to be influenced by the new conditions thus presented to our imagina- tion; so that Dr. Whewell's cruel hypothesis, though it did not touch the interests called scientific, would, if it could be proved, rob astronomers of half the fascination of their study.
The fascination of this half-belief, of course, increases as the con- ditions under which distant worlds exist are known to be really akin to our own. Dr. Whewell had no difficulty in alarming men's imagi- nations about life in Saturn, Uranus, or even Jupiter. He showed how dismal it would be for us, how little light and heat get thither from the sun, how very little firm footing there might be in worlds with a density very little greater, or even less (in the case of Saturn, less by nearly one-half), than water. He suggested that cork worlds or wood worlds were unlikely ; that probably the small weight meant fluid worlds ; and so, by very skilfully appealing to the English objection to damp, he pretty effectu- ally threw a wet blanket on the ardour of analogical reasoning in the case of the planets beyond Mars. But Dr. Whewell obviously felt himself that he had no very good case against the existence of beings even organized exactly like our- selves in Mars. Mars, though not absolutely the nearest of our planetary neighbours, is certainly—(of course, excluding the Moon, which is in many respects a world far more different in physical condition from the Earth than the proper planets)—more within our range of observation than any other attendant of the sun. Venus, no doubt the next of the planets to the Earth going sun- wards, is often nearer to the Earth than Mars, whose orbit envelopes our own, can ever be ; but the difficulty of observing a planet which is so bright that all the imperfections of our in- struments are exaggerated, and which, when at its nearest point to us must usually be observed at a low altitude, are so great, that we know less about Venus than about almost any other of the planets except Mercury. Mars, which can be observed, and has quite recently been closely observed by Mr. Lockyer, of Wimble- don, within the very moderate distance of about fifty millions of miles, is at present the only planet into the secrets of whose physical, as distinguished from purely mechanical structure, we can at present hope to peep. We know all about it that we know of any other planet, and a good deal more as well. We know that the day and night of all the four planets, Mercury, Venus, Earth, and Mars, are nearly of equal length, and considerably more than double the days and nights of the more distant and more elaborately moonlit (or ringlit) planets. We know that they are, all four, much heavier, bulk for bulk, than the bigger planets, the little Mercury being much the heaviest in material of the four ; we know that they all have atmospheres of greater or less density ; and we know very little more about any of them except Mars, But of Mars the observations of Messrs. Beer and Midler, in 1830, 1837, and 1841, had already given us a good deal of fresh knowledge, which Mr. Lockyer's admirable drawings, from observations made during the last autumn, have partly confirmed and partly supplemented.
Dr. Whewell's case against Mars chiefly consisted in its pre- sumed cold, and in a general improbability argument derived from the vast number of ages during which the Earth,— which is more favourably situated with regard to heat—had remained certainly untenanted by man. Of course to the last argument there is no reply, and no need for reply, as no one cares to believe that a planet is at this moment inhabited, but only to believe that it is prepared for the dwelling-place of rational beings. But with regard to the extreme cold of Mars, the assumption is probably quite unwarranted. A recent astronomer asserts that "water would not remain fluid even at the Martial equator, and alcohol would freeze at the temperate zones." Probably no assertion
was ever lees well grounded. The calculation is made on the prin- ciple that Mars is so much farther from the sun that the intensity of his rays is there only 4-9ths of their intensity here. That is true.
But then so much more depends on the collecting effect of a thick atmosphere than on the mere intensity of the sun's rays, that water will freeze on Mount Blanc, where the mere rays are cer- tainly much intenser, while it is summer heat in the valleys below. Accordingly, if the Martial atmosphere be only slightly denser than our own, the diminution in intensity would be in great measure compensated. So much for 6i priori reasoning. Now what is the fact ? The polar snows of Mars can be distinctly seep. A white spot of excessive brilliancy at the pole, which diminishes as the summer draws on, and enlarges again with winter, has been observed by many astronomers in Mars. How is this compatible with water freezing at its equator and alcohol at its temperate zone? Mr. Lockyer watched the south pole of Mars throughout last autumn. Early in last August the southern hemisphere of Mars would be entering on the season which corresponds with us to our May. In about a month's time, between August and September, he saw the white spot at the southern pole of Mars dwindle from about 20 deg. to 10 deg. In other words, the snow melted—for that this phenomenon is caused by the melting of the snow is scarcely doubted—from about 80 deg. south latitude up to 90 deg. south latitude, as the summer heat came on. The white spot was stationary, if not beginning to extend again before the observa- tions ceased, nearly three months after the polar snow had begun to dwindle. This is a very remarkable confirmation, and even exten- sion, of Beer and Mfidler's observations. They noted the decrease, but no decrease so rapid as that observed by Mr. Lockyer.
Mr. Lockyer's observations are also very interesting on the forms of what we may fairly call the oceans and inland seas of the southern hemisphere and equatorial regions of Mars. The obser- vations are so clearly defined and agree so well in general out- line, with all that have been made for the last thirty years, that it is at least quite certain that they are permanent features of the planet, and not merely bands of clouds. It is assumed that the permanent dark surfaces,—many of which, of exceedingly remarkable shapes, have now been verified again and again by successive observers,—represent either seas, or permanent rifts and chasms in the planet,—seas, of course, being much the more likely, — while the brighter regions indicate the more perfect reflection of light from the surface of continents or land,—the permanently dazzling spots being confined to the polar snows. If this be so, we can assert that several very remarkable seas,—including inland seas,—some of them con- nected, and some not connected by straits, with still larger seas, are now defined in the southern hemisphere, in which (as is the case also with the Earth) water seems to be much more widely spread than in the northern hemisphere. There is, for exam- ple, a southern sea exceedingly like our Baltic in shape. And there is another, and still more remarkable sea, now defined by the obser- vationsof many successive observers, near the equator,—a long strag- gling arm, twisting almost in the shape of an S laid on its back from east to west, which is at least a thousand miles in length and a hundred in breadth, as if a channel as wide as that between Liverpool and Dublin existed in equatorial Africa, and ran inland for a thousand miles or more. The masses of land in Mars appear to be least unbroken in the northern hemisphere,—but it is long since we have had any good opportunity of observing the northern hemisphere of Mars, as its year is so nearly equivalent to two earthly years, that it continually returns into proximity with the Earth, with the same southern pole towards us. The improved instruments of the last generation have therefore been employed as yet successfully only on the southern hemisphere.
There is every reason, then, to think that human life on Mars might be very much like human life on the Earth. The light cannot be so bright, but the organs of sight may be so much more susceptible as to make the vision quite as good. The heat is probably leas, as the polar snows certainly extend further; but by no means leas in proportion to the lessened power of the solar rays. The density of the rocks and geological strata is very nearly the same, and the peculiar red colour of the planet has sometimes been ascribed to a preponderance of red sandstone. The weight of bodies there is nearly half what it is on our Earth, so that muscular Christianity, if it exist there, produces much greater apparent effects for the same amount of effort. The whole condensation of society may be greater, since the surface of the planet is one quarter only of the surface of the Earth—a moral advantage, as we conceive it, to which only Americans, with their quantitative ideas of civilization, will be blind. It would appear at present that there is less sea and more land in proportion, on Mars than on the Earth; but of this we are scarcely yet competent to judge ; and if it be so, this is, we fear, a disadvantage to our Martial neightours, as the sea has always proved anything but "dissociating," as Horace calls it, in the later stages of civilization. Finally, the Martialites (if Martialites there be) have probably no moon, but get an additional half-hour in every diurnal revolution to make up for this disadvan- tage, and their year is twice as long as ours ; so that their thoughts and actions have probably a longer stroke, as we may say ; that is, they have less temptation to be constantly taking stock of their progress.
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