Percival Lowell

“ That we are the only minds in space it takes indeed a very small mind to fancy. Our relative insignificance commonly escapes us. If we reduce the universe to a scale on which we can conceive it, that on which the earth shall be represented by a good-sized pea, with a grain of mustard seed, the moon, circling about it at a diameter of seven inches, the sun would be a globe two feet in diameter, two hundred and twenty feet away. Mars, a much smaller pea, would circle round the two-foot globe, three hundred and fifty feet from its surface; Jupiter, an orange, at a distance of a quarter of a mile ”

“ We see the principle exemplified in our terrestrial clouds; the low nimbus being formed of comparatively large globules, while the high cirrus is made up of very minute particles. If we go yet higher, we reach a region incapable of supporting clouds of any kind, so rarefied is its air. This occurs about five miles above the earth's surface; and yet even at this height the density of our air is greater than is the probably density of the air at the surface of Mars. We see, therefore, that the Martian atmosphere should from its rarity prove cloudless, just as we observe it to be. ”

“ But now, if the body's departure were even hastier than this, the earth would never be able wholly to annihilate its speed, and the body would travel forever away out and out, till it fell, probably, under the sway of some distant star. In any case, the earth would know the vagabond no more.
As gravity, depends upon mass, the larger the attracting planet, the greater is its critical velocity, the velocity it can just control; and, reversely, the smaller the planet, the less its restraining power. With the earth the critical velocity is between six and seven miles a second. ”

“ To each molecule in turn would come this happy dispatch, till the earth stood deprived of every atom of free hydrogen she possessed.
It is a highly significant fact that there is no free hydrogen found in the earth's atmosphere. With oxygen and water vapor, and indeed all the other gases we know, the case if different; for their maximum speed falls far short of the possibility of escape. So they have stayed with us solely because they must. And, as a matter of fact, the earth's atmosphere contains plenty of free oxygen, nitrogen, and the like. ”

“ Neither the hour of his day nor the season of his year brings change in them. They slowly, very slowly, alter in appearance, indeed, but not in obedience to that central ruler that gathers and dispels our own. In short, the Jovian clouds are not sun-raised, but self-raised ones. It is heat inherent in Jupiter himself, not heat from the sun, that belts him about with his great girdles of cloud. ”

“ Here, then, we have a very curious phenomenon, a phenomenon which seems to indicate that the seasonal wave of change acts as a unit across the planet's face; that instead of a more or less continuous deposit of moisture at the pole, such as occurs on earth, Martian atmospheric conditions oblige such deposit to creep gradually with the season up into polar latitudes, where it appears first as a crown of frost, and does not envelop the pole and become a polar cap till it has got higher. ”

“ Without it, not only development, but decay would come to a standstill, when once all that was friable land crumbled to pieces under the alternate roasting and refrigerating to which the planet's surface would be exposed as it revolved upon its axis toward and away from the sun. Disintegration once effected, the planet would roll, a mummy world, through space. ”

“ A cloud is an event on Mars, a rare and unusual phenomenon, which should make it more fittingly appreciated there than Ruskin lamented was the case on earth. For it is almost perpetually fine weather on our neighbor in space. From the days beginning to its close, and from one end of a year to the other, nothing appears to veil the greater part of the planet's surface. ”

“ If, therefore, free hydrogen were present at the surface of the earth, and met with no other gas attractive enough to tie it down by uniting with it, the rover would, in course of time, attain a speed sufficient to allow it to bid good-by to earth, and start on interspacial travels of its own. That it should reach its maximum speed is all that is essential to liberty, the direction of its motion being immaterial. ”

“ Incapacity to quarter folk is included in the more general incapacity to hold an atmosphere; for absence of atmosphere precludes the possibility of life as we know it. That a planet may be too small to have an atmospheric envelope we shall see more definitely later. That life, however, of a type of which we have no conception may not exist in all these orbs we must be wary of stating, for nothing is more dangerous than a general denial, except a particular statement.
We are limited, therefore, in our present inquiry, to Venus and Mars. ”

“ The same state of things is yet more strikingly instanced by Saturn; for the tilt of Saturn's pole is not very unlike that of the earth, and in consequence his equatorial regions are at times raised far above the plane of his orbit; at others, dipped far below it. Yet unlike the earth's cloud-belts, his never travel northward when the sun goes north, nor follow the sun when he journeys south again. So far as the sun is concerned, the Saturnian cloud-belts are invariable. Like the Jovian, they owe their formation to the planet's own heat. Like Jupiter, too, Saturn, shows red beneath. ”

“ To sum up, now, what we know about the atmosphere of Mars: we have proof positive that Mars has an atmosphere; we have reason to believe that this atmosphere is very thing,—thinner at least by half than the air upon the summit of the Himalayas,—that in constitution it does not differ greatly from our own, and that it is relatively heavily charged with water vapor. ”

“ AMID the seemingly countless stars that on a clear night spangle the vast dome overhead, there appeared last autumn to be a new-comer, a very large and ruddy one, that rose at sunset through the haze about the horizon. ”

“ Since atmosphere, therefore, is a sine qua non to any change upon a planet's surface is proof positive of the presence of an atmosphere, however incapable of detection such atmosphere be by direct means.
Now changes take place upon the surface of Mars, changes vast enough to be visible from the earth. When properly observed they turn out to be most marked. We will begin with the look of the planet last June. Its general aspect then was tripartite. Upon the top part of the disc, round what we know to be the planet's pole, appeared a great white cap, the south polar cap. ”

“ But even the earth is not omnipotent. As the velocity with which the body is projected increases, it takes the earth longer and longer to overcome it and compel the body's return. Finally there comes a speed which the earth is just able to overcome, if she take an infinite time about it. In that case, the body would continue to travel away from her, at a constantly diminishing rate, but still at some rate, on and on into the depths of space, till it attained infinity, at which point the truant would stop, and reluctantly begin to return again. This velocity we may call the critical velocity. ”

“ A fish doubtless imagines life out of water to be impossible; and similarly, to argue that life of an order as high as our own, or higher, is impossible, because of less air to breathe than that to which we are locally accustomed, is, as Flammarion happily expresses it, to argue, not as a philosopher, but as a fish. ”

“ At thirty degrees in from the limb the observer would look through twice as much of it as when he looked plumb down upon the centre of the disc; in consequence, what would be diaphanous at the centre might well seem opaque toward the edge. The effect we are familiar with on earth in the haze that always borders the horizon,—a haze most noticeable in places where there is much water in the air. Here, then, we have a hint of what is the matter on Mars. Were his atmosphere charged with water-vapor, just such an effect as is observed should take place. ”

“ Clouds are congeries of globules of water or particles of ice buoyed up by the air about them. The smaller these are, the more easily are they buoyed up, because gravity, which tends to pull them down, acts upon their mass, while the resistance they oppose to it varies as their surface, and this, as we saw just now, is relatively greater in the smaller particles. The result is that the smaller particles can float in thinner air. ”

“ Unlike New England, which has more than it can accommodate, Mars has none of the article. What takes its place as the staple topic of conversation for empty-headed folk remains one of the Martian mysteries yet to be solved. What takes its place in fact is a perpetual serenity, such as we can scarcely conceive of. Although over what we shall later see to be the great continental deserts the air must at midday be highly rarefied, and cause vacuums into which the surrounding air must rush, the actual difference gradient owing to the initial thinness of the air must be very slight. ”

“ In the first place, if we are right, there can be no rain, nor hail, nor snow in them, for the particles would be deposited before they gained the dignity of such separate existence. Dew or frost would be the maximum of precipitation that Mars could support. The polar snow-cap or ice-cap, therefore, is doubtless formed, not by the falling of snow, but by successive depositions of dew. ”

“ With Mercury littleness is even more fatal to life; for though the giant planets may perhaps, at some future day, grow to be life-supporting, a small one apparently never was, nor ever can be, peopled by beings in the least resembling us. ”

“ So much for matter. As for mind beyond the confines of our tiny globe, modesty, backed by a probability little short of demonstration, forbids the thought that we are the sole thinkers in this great universe. ”

“ From him, therefore, of all the heavenly bodies, may we expect first to learn something beyond celestial mechanics, beyond even celestial chemistry; something in answer to the mute query that man instinctively makes as he gazes at the stars, whether there be life in worlds other than his own. ”

“ By stripping off layer after layer we reach eventually a last layer which is all surface, inclosing nothing. We may, if we please, observe something analogous in men, among whom the most superficial have the least in them. In consequence of this principle, the atmosphere of the smaller body finds itself obliged to cover relatively more surface, which still further thins it out. ”

“ Matter proves to be common property. We have learnt that the very same substances with which we are familiar on this our earth, iron, magnesium, calcium, and the rest, are present in the far-off stars that strew the depths of space. ”

“ One deduction from this thin air we must, however, be careful not to make: that because it is thin it is incapable of supporting intelligent life. That beings constituted physically as we are would find it a most uncomfortable habitat is pretty certain. But lungs are not wedded to logic, and there is nothing in the world or beyond it to prevent, so far as we know, a being with gills, for example, from being a most superior person. ”

“ From all this it is pretty plain that the giant planets are far from pleasurable abodes, as yet midway in evolution between actual suns and tenantable worlds; too cooled down for the one state, and not yet cooled down enough for the other. ”

“ The molecular theory of gases supposes them to be made up of myriads of molecules in incessant motion. What a molecule may be nobody knows; some scientists supposing it to be a vortex ring in miniature,—something like the swirl produced by a teaspoon when drawn through a cup of tea. ”

“ Hitherto the question has received no affirmative reply, although the trend of all latter-day investigation has been to such affirmation; for science has been demonstrating more and more clearly the essential oneness of the universe. ”

“ So low a boiling-point would make it impossible to cook anything in the open air. Boiled eggs could be prepared only under cover, and such people as liked their meat boiled would probably find it convenient to prefer it done differently. Fortunately, roasts would still remain possible. The lowering of the boiling-point would raise the relative amount of aqueous vapor held in suspension by the air at any temperature. ”

“ This first hint receives an independent support from another Martian phenomenon. Contrary to what the distance of the planet from the sun and the thinness of its atmospheric envelope would lead us to expect, the climate of Mars proves astonishingly mild. Whereas calculation from distance and atmospheric density puts its average temperature below freezing, thus relegating it to perpetual ice, the planetÕs surface features show that the temperature is relatively high. Observation reveals the fact that the mean temperature must actually be above that of the earth ”

“ With a normal barometer of four and a half inches, a very great relative fall is a very slight actual one. In consequence, storms would such mild-mannered things that, for objectionable purposes, they might as well not be. ”

“ That they are not storm-clouds, like those which, by a wavelike process of generation, travel across the American continent, for example, is shown by the fact that they do not travel, but are local fixtures. ”