Does Life Exist on Mars?

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Nature Magazine, February 1948

The report of Dr. G. P. Kuiper, Director of the McDonald Observatory, that examination of the infra-red spectrum of Mars revealed the presence of carbon dioxide in the atmosphere of Mars in an amount equal to, or even somewhat greater than in the earth's atmosphere, is of great importance and interest. The additional discovery that no other gases with strong absorption in the infra-red were present, such as the poisonous gases methane and ammonia found in such abundance in the atmosphere of the outer planets, further strengthens the belief in the possibility of life on Mars. The presence of carbon dioxide in the atmosphere is essential to the growth of plant life, and it shows that the Martian atmosphere also absorbs more heat and has a greater blanketing effect than would be possible without its presence. As carbon dioxide is also a product of animal life, its presence in the Martian atmosphere suggests the possibility of animal as well as plant life on the planet. This is especially possible since oxygen, as essential to animal life as carbon dioxide is to plant life, has been found in the atmosphere of Mars, although occurring by no means as extensively as in the earth's atmosphere. The presence of carbon dioxide in the atmosphere of Mars explodes the theory, so often advanced by those who opposed the belief in the existence of life on Mars, that the polar caps consisted of frozen carbon dioxide instead of ice or snow.

On February 17 Mars will be at opposition and also nearest to the earth for this particular Martian year, although at the most unfavorable of all oppositions. The distance from the earth of approximately 63,000,000 miles on that date will not be exceeded at any opposition by more than a few thousand miles, while at a favorable opposition, such as will not occur again for several more periods of revolution, relative to the earth of 780 days each, the planet will be less than 35,000,000 miles distant. This does not rule out the possibility, however, that much interesting and valuable information may be acquired regarding this small planetary neighbor of ours before the next most favorable opposition.

The discovery of carbon dioxide in the atmosphere of Mars was made with a new type of infra-red spectrometer that contains a small cell sensitive to the infra-red spectrum. It was this spectrometer, also, that proved the non-existence in the atmosphere of Mars of poisonous gases with strong infra-red radiations. It is probable that the greater part of the atmosphere of Mars consists of nitrogen, which has no bands in this part of the spectrum. During this month, when the white polar cap of Mars and dark regions, greenish in color, are studied with the new spectrometer under the most favorable conditions for this opposition, new facts may be discovered that will help to solve the problem of the possibility of life on other worlds.

It may not be long now before one of the longest controversies among astronomers – one that has lasted for seventy years – may finally be solved through the immense light-gathering power of the 200-inch Mt. Palomar telescope. Ever since the Italian astronomer Schiaparelli, in 1877, announced the discovery of a network of fine, hair-like lines on the surface of Mars, there have been two groups of observers who have flatly contradicted each other as to the objectivity of these "canals," as they were called. According to Dr. Edwin Hubble of the Mt. Wilson Observatory, in a lecture delivered in Pasadena, California, in April 1947, on some problems that may be solved by the new telescope, it may soon be possible to photograph with this instrument all that the eye can see with a telescope of moderate size, because of the great light-gathering power of this telescope. If the canal system can be shown to be real, Dr. Hubble states, it would almost necessarily imply the existence now, or in the past, of intelligent beings on Mars. Although many observers of Mars have made drawings of the canals, glimpsed in moments of superlative seeing, it has been impossible so far to photograph the canal pattern. These consist of many fine dark lines that appear, when viewed visually in even moderate-sized telescopes, to run along arcs of great circles and converge or cross at spots called "oases."

There are a number of reasons why photography of the canals of Mars has so far been unsuccessful. The light gathered from the planet's surface at the primary focus of even the powerful Mt. Wilson reflector gives so small an image that an enlarging lens of considerable power must be used to obtain an image suitable for photographing. This means that the light is greatly reduced, to begin with, by being spread over a large area. In addition, the red or orange filters used in the photography of the planet produce a still further reduction of light. It follows that time exposures are necessary. Even though these exposures may be only a second or so in duration, the dancing of the image due to atmospheric effects is generally so great even in this short period of time that it may be fatal to a delineation of the intricate detail and thread-like imagery of the canal system. The human eye has the advantage that, even with a moderate-sized telescope and less magnification of the image, it may seize upon the rare moments of perfect seeing to glimpse and record the appearance of the network of canals that have been depicted in drawings by many different observers. It is to the great light gathering power of the 200-inch telescope that astronomers now turn with the hope that finally the much debated question of the objective reality of the canals of Mars may be settled. Should the existence of such an elaborate and intricate system be established beyond doubt, then its artificial appearance and geometric regularity show clearly that intelligent beings have accomplished a great engineering feat on this neighboring world. The scarcity of water on Mars, evident from the nature of its surface markings, which reveal the existence of large, reddish, desert-like areas, would require a careful conservation and economical distribution and control of all available supply. It would be to the seasonal melting of the polar caps that the inhabitants of the planet would look for the chief source of their water supply, and the canal system could be the great irrigation system of the planet designed to distribute this meager supply where it would be most needed.

Compared to our own planet, small as it is itself, Mars is a tiny world. It has a mass only one-tenth that of the earth and a diameter of 4200 miles, not much more than half that of the earth. The surface gravity is so low compared to that of the earth that a man weighing 150 on earth would weigh only about 60 pounds on Mars. The surface area of Mars equals the land area of the earth. About one-tenth of the land area of the earth is desert.

On Mars more than half of the surface area is a desert region, giving the planet its deeply reddish tinge. There are apparently no oceans or lakes. There are, however, dark greenish or bluish-gray regions that cover about three-eighths of the surface. These regions change in color with the Martian seasons – which are very similar to our own although nearly twice as long – darkening with the coming of spring and the melting of the white polar cap. White areas, apparently consisting of clouds, hoar frost, or haze, come and go transiently over the surface. The canals have been traced by many observers across the reddish as well as dark regions of the planet, criss-crossing the surface in all directions, and a number of them meeting in the dark spots called oases, which may be as much as 100 miles across. Doubling of the canals in some instances has been noted. Such canals appear as fine lines 100 or 200 miles apart and equidistant their entire length.

The atmosphere of Mars is, to be sure, much less dense than our own, but, nevertheless, an atmosphere does exist on this planet and it does contain both oxygen and carbon dioxide, and no poisonous gases such as exist on the outer planets. It has been found that the atmospheric temperature at the equator of the planet is about like that of a spring day on the earth in mid-Iatitudes. When one considers all of these facts, as well as the nature of the surface markings on the planet, the seasonal changes and length of day, so similar to that of our own planet, one finds it difficult to escape from the belief that life must exist on this other world.

The planet Saturn, as well as Mars, will be in opposition to the sun this month. Saturn is now in Leo, a few degrees west of Regulus, and, at the beginning of the month, Mars is about equally far to the east of Regulus, in Leo. The two planets will draw closer together as the month advances. Saturn is now about as brilliant as Vega, but Mars, now at its brightest, is about equal to Canopus in brilliance throughout the month. Saturn will be in opposition and visible all night on February 9. Mercury will be at greatest elongation east of the sun on February 4, and this is the most favorable time of the year to see it in the evening sky. It should be visible in the evening twilight for a week or ten days the first of the month, and should be a little south of west. It will be more brilliant than Vega or Capella when at elongation.

Venus is now in the western sky in the early evening and is drawing away from the sun and improving its position gradually. Jupiter is now visible in the eastern sky before sunrise in the constellation of Ophiuchus until the end of the month, when it passes into Sagittarius.