This is the only proof of the existence of water he adduces, and it is certainly a most extraordinary and futile one. For it is perfectly well known that although water, in large masses and by transmitted light, is of a blue colour, yet shallow water by reflected light is not so; and in the case of the liquid produced by the snow-caps of Mars, which the whole conditions of the planet show must be shallow, and also be more or less turbid, it cannot possibly be the cause of the 'deep blue' tint said to result from the melting of the snow.

But there is a very weighty argument depending on the molecular theory of gases against the polar caps of Mars being composed of frozen water at all. The mass and elastic force of the several gases is due to the greater or less rapidity of the vibratory motion of their molecules under identical conditions. The speed of these molecular motions has been ascertained for all the chief gases, and it is found to be so great as in certain cases to enable them to overcome the force of gravity and escape from a planet's surface into space. Dr. G. Johnstone Stoney has specially investigated this subject, and he finds that the force of gravity on the earth is sufficient to retain all the gases composing its atmosphere, but not sufficient to retain hydrogen; and as a consequence, although this gas is produced in small quantities by volcanoes and by decomposing vegetation, yet no trace of it is found in our atmosphere. The moon however, having only one-eightieth the mass of the earth, cannot retain any gas, hence its airless and waterless condition.

Water Vapour cannot exist on Mars.

Now, Dr. Stoney finds that in order to retain water vapour permanently a planet must have a mass at least a quarter that of the earth. But the mass of Mars is only one-ninth that of the earth; therefore, unless there are some special conditions that prevent its loss, this gas cannot be present in the atmosphere. Mr. Lowell does not refer to this argument against his view, neither does he claim the evidence of spectroscopy in his favour. This was alleged more than thirty years ago to show the existence of water-vapour in the atmosphere of Mars, but of late years it has been doubted, and Mr. Lowell's complete silence on the subject, while laying stress on such a very weak and inconclusive argument as that from the tinge of colour that is observed a little distance from the edge of the diminishing snow-caps, shows that he himself does not think the fact to be thus proved. If he did he would hardly adduce such an argument for its presence as the following: "The melting of the caps on the one hand and their re-forming on the other affirm the presence of water-vapour in the Martian atmosphere, of whatever else that air consists" (p. 162). Yet absolutely the only proof he gives that the caps are frozen water is the almost frivolous colour-argument above referred to!

No Spectroscopic Evidence of Water Vapour.

As Sir William Huggins is the chief authority quoted for this fact, and is referred to as being almost conclusive in the third edition of Miss Clerke's History of Astronomy in 1893, I have ascertained that his opinion at the present time is that "there is no conclusive proof of the presence of aqueous vapour in the atmosphere of Mars, and that observations at the Lick Observatory (in 1895), where the conditions and instruments are of the highest order, were negative." He also informs me that Marchand at the Pic du Midi Observatory was unable to obtain lines of aqueous vapour in the spectrum of Mars; and that in 1905, Slipher, at Mr. Lowell's observatory, was unable to detect any indications of aqueous vapour in the spectrum of Mars.

It thus appears that spectroscopic observations are quite accordant with the calculations founded on the molecular theory of gases as to the absence of aqueous vapour, and therefore presumably of liquid water, from Mars. It is true that the spectroscopic argument is purely negative, and this may be due to the extreme delicacy of the observations required; but that dependent on the inability of the force of gravity to retain it is positive scientific evidence against its presence, and, till shown to be erroneous, must be held to be conclusive.

This absence of water is of itself conclusive against the existence of animal life, unless we enter the regions of pure conjecture as to the possibility of some other liquid being able to take its place, and that liquid being as omnipresent there as water is here. Mr. Lowell however never takes this ground, but bases his whole theory on the fundamental identity of the substance of the bodies of living organisms wherever they may exist in the solar system. In the next two chapters I shall discuss an equally essential condition, that of temperature, which affords a still more conclusive and even crushing argument against the suitability of Mars for the existence of organic life.

Страница 8 из 23

Назад 1…7 8 9…23 Далее

Is Mars habitable? A critical examination of Professor Percival Lowell&apos;s book &quot;Mars and its canals,&quot; with an alternative explanation

AI-разбор доступен после входа

О книге

Читать онлайн

Is Mars habitable? A critical examination of Professor Percival Lowell's book "Mars and its canals," with an alternative explanation