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Is Mars Habitable?
This small volume was commenced as a review article on ProfessorPercival Lowell's book, Mars and its Canals, with the object ofshowing that the large amount of new and interesting facts contained inthis work did not invalidate the conclusion I had reached in 1902, andstated in my book on Man's Place in the Universe, that Mars was nothabitable.
But the more complete presentation of the opposite view in the volumenow under discussion required a more detailed examination of the variousphysical problems involved, and as the subject is one of great, popular,as well as scientific interest, I determined to undertake the task.
This was rendered the more necessary by the fact that in July lastProfessor Lowell published in the Philosophical Magazine an elaboratemathematical article claiming to demonstrate that, notwithstanding itsmuch greater distance from the sun and its excessively thin atmosphere,Mars possessed a climate on the average equal to that of the south ofEngland, and in its polar and sub-polar regions even less severe thanthat of the earth. Such a contention of course required to be dealtwith, and led me to collect information bearing upon temperature in allits aspects, and so enlarging my criticism that I saw it would benecessary to issue it in book form.
Two of my mathematical friends have pointed out the chief omission whichvitiates Professor Lowell's mathematical conclusions—that of a failureto recognise the very large conservative and cumulative effect of adense atmosphere. This very point however I had already myself discussedin Chapter VI., and by means of some remarkable researches on the heatof the moon and an investigation of the causes of its very lowtemperature, I have, I think, demonstrated the incorrectness of Mr.Lowell's results. In my last chapter, in which I briefly summarise thewhole argument, I have further strengthened the case for very severecold in Mars, by adducing the rapid lowering of temperature universallycaused by diminution of atmospheric pressure, as manifested in thewell-known phenomenon of temperate climates at moderate heights evenclose to the equator, cold climates at greater heights even on extensiveplateaux, culminating in arctic climates and perpetual snow at heightswhere the air is still far denser than it is on the surface of Mars.This argument itself is, in my opinion, conclusive; but it is enforcedby two others equally complete, neither of which is adequately met byMr. Lowell.
The careful examination which I have been led to give to the whole ofthe phenomena which Mars presents, and especially to the discoveries ofMr. Lowell, has led me to what I hope will be considered a satisfactoryphysical explanation of them. This explanation, which occupies the wholeof my seventh chapter, is founded upon a special mode of origin forMars, derived from the Meteoritic Hypothesis, now very widely adopted byastronomers and physicists. Then, by a comparison with certainwell-known and widely spread geological phenomena, I show how the greatfeatures of Mars—the 'canals' and 'oases'—may have been caused. Thischapter will perhaps be the most interesting to the general reader, asfurnishing a quite natural explanation of features of the planet whichhave been termed 'non-natural' by Mr. Lowell.
Incidentally, also, I have been led to an explanation of the