Astronomy of To-day: A Popular Introduction in Non-Technical Language

by Cecil Goodrich Julius Dolmage

It is the idea of life on Mars which has given this planet such a fascination in the eyes of men. A great deal of nonsense has, however, been written in newspapers upon the subject, and many persons have thus been led to think that we have obtained some actual evidence of the existence of living beings upon Mars. It must be clearly understood, however, that Professor Lowell's advocacy of the existence of life upon that planet is by no means of this wild order. At the best he merely indulges in such theories as his remarkable observations naturally call forth. His views are as follows:—He considers that the planet has reached a time when "water" has become so scarce that the "inhabitants" are obliged to employ their utmost skill to make their scanty supply suffice for purposes of irrigation. The changes of tone and colour upon the Martian surface, as the irrigation produces its effects, are similar to what a telescopic observer—say, upon Venus—would notice on our earth when the harvest ripens over huge tracts of country; that is, of course, if the earth's atmosphere allowed a clear view of the terrestrial surface—a very doubtful point indeed. Professor Lowell thinks that the perfect straightness of the lines, and the geometrical manner in which they are arranged, are clear evidences of artificiality. On a globe, too, there is plainly no reason why the liquid which results from the melting of the polar caps should trend at all in the direction of the equator. Upon our earth, for instance, the transference of water, as in rivers, merely follows the slope of the ground, and nothing else. The Lowell observations show, however, that the Martian liquid is apparently carried from one pole towards the equator, and then past it to the other pole, where it once more freezes, only to melt again in due season, and to reverse the process towards and across the equator as before. Professor Lowell therefore holds, and it seems a strong point in favour of his theory, that the liquid must, in some artificial manner, as by pumping, for instance, be helped in its passage across the surface of the planet.

A number of attempts have been made to explain the doubling of the canals merely as effects of refraction or reflection; and it has even been suggested that it may arise from the telescope not being accurately focussed.

The actual doubling of the canals once having been doubted, it was an easy step to the casting of doubt on the reality of the canals themselves. The idea, indeed, was put forward that the human eye, in dealing with detail so very close to the limit of visibility, may unconsciously treat as an actual line several point-like markings which merely happen to lie in a line. In order to test this theory, experiments were carried out in 1902 by Mr. E.W. Maunder of Greenwich Observatory, and Mr. J.E. Evans of the Royal Hospital School at Greenwich, in which certain schoolboys were set to make drawings of a white disc with some faint markings upon it. The boys were placed at various distances from the disc in question; and it was found that the drawings made by those who were just too far off to see distinctly, bore out the above theory in a remarkable manner. Recently, however, the plausibility of the illusion view has been shaken by photographs of Mars taken during the opposition of 1905 by Mr. Lampland at the Lowell Observatory, in which a number of the more prominent canals come out as straight dark lines. Further still, in some photographs made there quite lately, several canals are said to appear visibly double.

Following up the idea alluded to in [Chapter XVI.], that the moon may be covered with a layer of ice, Mr. W.T. Lynn has recently suggested that this may be the case on Mars; and that, at certain seasons, the water may break through along definite lines, and even along lines parallel to these. This, he maintains, would account for the canals becoming gradually visible across the disc, without the necessity of Professor Lowell's "pumping" theory.

And now for the views of Professor Lowell himself with regard to the doubling of the canals. From his observations, he considers that no pairs of railway lines could apparently be laid down with greater parallelism. He draws attention to the fact that the doubling does not take place by any means in every canal; indeed, out of 400 canals seen at Flagstaff, only fifty-one—or, roughly, one-eighth—have at any time been seen double. He lays great stress upon this, which he considers points strongly against the duplication being an optical phenomenon. He finds that the distance separating pairs of canals is much less in some doubles than in others, and varies on the whole from 75 to 200 miles. According to him, the double canals appear to be confined to within 40 degrees of the equator: or, to quote his own words, they are "an equatorial feature of the planet, confined to the tropic and temperate belts." Finally, he points out that they seem to avoid the blue-green areas. But, strangely enough, Professor Lowell does not so far attempt to fit in the doubling with his body of theory. He makes the obvious remark that they may be "channels and return channels," and with that he leaves us.

The conclusions of Professor Lowell have recently been subjected to strenuous criticism by Professor W.H. Pickering and Dr. Alfred Russel Wallace. It was Professor Pickering who discovered the "oases," and who originated the idea that we did not see the so-called "canals" themselves, but only the growth of vegetation along their borders. He holds that the oases are craterlets, and that the canals are cracks which radiate from them, as do the rifts and streaks from craters upon the moon. He goes on to suggest that vapours of water, or of carbonic acid gas, escaping from the interior, find their way out through these cracks, and promote the growth of a low form of vegetation on either side of them. In support of this view he draws attention to the existence of long "steam-cracks," bordered by vegetation, in the deserts of the highly volcanic island of Hawaii. We have already seen, in an earlier chapter, how he has applied this idea to the explanation of certain changes which are suspected to be taking place upon the moon.

In dealing with the Lowell canal system, Professor Pickering points out that under such a slight atmospheric pressure as exists on Mars, the evaporation of the polar caps—supposing them to be formed of snow—would take place with such extraordinary rapidity that the resulting water could never be made to travel along open channels, but that a system of gigantic tubes or water-mains would have to be employed!

As will be gathered from his theories regarding vegetation, Professor Pickering does not deny the existence of a form of life upon Mars. But he will not hear of civilisation, or of anything even approaching it. He thinks, however, that as Mars is intermediate physically between the moon and earth, the form of life which it supports may be higher than that on the moon and lower than that on the earth.