Is there Life on Mars - Mars information from 1925
"WHY SHOULD MARS ATTRACT so much interest as it does? "asks Dr. Robert G. Aitken, associate director of the Lick Observatory, in a recent leaflet issued by the Astronomical Society of the Pacific (San Francisco).
It is by no means the largest of the planets; on the contrary, it is next to the smallest. It has only two tiny moons, as compared with the nine each that revolve about Jupiter and Saturn. It is not even the planet that is nearest the earth, for at its least distance it is 35,000,000 miles away, whereas Venus comes within 26,000,000 miles of us every other year. Dr. Aitken goes on:
"So far as astronomers are concerned many answers could be given, but in my opinion the chief, if not the only, reason for the great popular interest in Mars is that, more than any other planet, it has become associated in our minds with the question of the possibility that life may exist on other worlds than on our little Earth.
"What evidence have astronomers secured on this question, and, in particular, what gain in knowledge has resulted from their study of the planet at the opposition of August, 1924, when it was nearer to the earth than it had been for over a century or than it will be for a century to come?
"Briefly, we know that the Martian day is practically equal to our own; that on Mars the seasons—spring, summer, autumn and winter—closely resemble our own, except that they are nearly twice as long because the Martian year equals 22 1/2 of our months. These facts are beyond dispute. Astronomers almost unanimously agree also: that there is an atmosphere on the planet which contains water vapor; that the polar caps, which grow as the Martian winter deepens and shrink as the summer comes on, are frozen water in some form; that a large number of the markings seen on the planet are permanent and, therefore, on the actual surface; but that there are no permanent bodies of water on Mars resembling our oceans or even our great lakes. Here agreement ends. There has been great diversity of opinion as to the extent and character of the atmosphere, as to the temperature and range of temperature, and, above all, as to the nature and interpretation of the surface markings. This difference of opinion is not surprizing, for the image of Mars even in a powerful telescope is hardly larger than the disk of the moon as seen with the naked eye; and the very largest direct photographs that I have seen (before enlargement in the dark room) are much smaller than a silver dime. Further, our own turbulent atmosphere, as well as whatever atmosphere exists on Mars, interferes sadly with all our views of the planet's surface.
"The question of the habitability of Mars turns upon the points in dispute; for the facts on which all are agreed (except the non-existence of oceans and lakes) are all favorable to the view that life may exist there. The recent observations have done something to clear up the situation.
"In the first place, photographic studies at many observatories, and especially at the Lowell Observatory, demonstrate that numerous details of the surface markings—and, in particular, of the large dark areas in the southern hemisphere, which is the one turned toward us whenever Mars is best situated for observation—vary with the Martian season. The color of these dark areas, too, is definitely greenish in the Martian spring and is of a neutral (some say brownish) tint in the Martian autumn. These observations find a reasonable explanation in the hypothesis that the dark areas are covered with vegetation; and if that view is correct, then low forms of animal life are almost certainly present, for on the earth animal life is never absent from areas of extensive vegetation.
"In the second place, at the Lowell and Mount Wilson observatories, very sensitive thermoelectric instruments were used to measure the radiation from Mars and thus determine the temperature at its surface. The problem is an extremely difficult one, because we must distinguish between the radiation simply reflected by the planet, as by a mirror, and the radiation that comes from heat absorbed by the planet and its atmosphere, and must also take into account the absorptive effect of our own atmosphere. Moreover, the measures do not give us the temperature directly; we must make some assumption as to how the planet radiates the heat that may fall upon it.
"It is hardly to be wondered at, therefore, that the results from the two observatories are not in complete agreement. The significant fact is not that they differ, but that they differ so little. At Mount Wilson it was found that the temperature at the center of the illuminated disk is slightly above freezing, perhaps 40 degrees Fahrenheit; at Flagstaff, that it resembles the temperature of the earth on a clear, cool day, say from 45 to 60 degrees Fahrenheit, or possibly a little higher. The night temperature, the temperature at the poles, and the winter temperature, must naturally be far lower, probably much below the corresponding values on our earth. The significant fact, however, is, as I have said, that both investigations give a maximum temperature definitely above freezing.
"When we recall that the Martian spring and summer are nearly twice as long as our own, and that the seeds of many low forms of vegetable life on earth are adapted to endure extreme cold, this temperature seems moderately favorable to life of such forms, however unfavorable it may be to higher forms.
"Again, photographs of the planet in light of different colors taken at various observatories, and in particular at the Lick Observatory, show significant differences. Photographs on ordinary plates, which are sensitive to short wave-length violet light, show practically no detail except the polar cap; those taken on red-sensitive (long wave-length light) plates, on the contrary, show a large amount of detail. The polar cap is smaller, and the entire image about 5 per cent. smaller, on these plates than on the ordinary violet-sensitive photographic plates. Photographs of San Jose, taken from Mount Hamilton on a day when a dry haze hid the city almost completely from our view, indicate a possible interpretation of these differences. The ordinary photographic plates give no detail of San Jose; the red-sensitive plates show the individual houses in the city, and almost the windows in the houses. Obviously, the red rays penetrated the hazy atmosphere; the violet rays did not.
"If the atmosphere of Mars has a similar selective effect upon light of different wave-lengths, then the photographs by red light show the actual surface details, those by violet light only the outer atmosphere. The difference in diameter, then, is due to this atmosphere and indicates that it is of greater extent than had heretofore been accepted. This deduction is not a proved fact, but is a plausible inference based upon the observed differences in the Martian and terrestrial photographs.
"Finally, I think it fair to say that the detailed visual and photographic study of the surface markings at the recent opposi-tion has not changed the opinion of the majority of astronomers that these markings are probably of natural, and not of artificial, origin; they do not indicate the existence of intelligent life on Mars. We must, therefore, conclude that, so far as temperature and the presence of water and atmosphere are concerned: Mars may be a habitable globe and the dark areas may be evidences of vegetation, tho this is not beyond question, but we have no definite evidence whatever to argue for the existence of intelligent life on the planet.
"We have no hope at all of discovering evidence that intelligent life exists on any of the other planets in the solar system. Does that mean that we should regard our earth as the only planet sustaining intelligent life? I think not.
"I think that would be the most egotistical and anthropocentric conclusion we could imagine. Our sun is only one of several thousand million suns in our universe; it is not conspicuous for its size, nor unique in its location (for it is many hundreds of light years from the center of the stellar system) nor distinguishable from thousands of other stars by the quality of its light. Moreover, all of these millions of suns are composed of elements identical with those known here on our earth. Must there not among them be many having planets that are not only capable of sustaining life, but that have intelligent beings dwelling upon them? I think an affirmative answer is the only reasonable conclusion, even tho we may never be able to establish it by direct observation."
Source: The Literary Digest for August 22, 1925