1843 - Of Mars, our precise knowledge is little. It has an atmosphere not unlike that of the earth- certainly not more extensive,and probably clearer. Its day and night are almost of the duration of ours, and its surface is divided into continents and seas, whose complete outline we have not been able to trace. PLATE XII- for which Astronomy is indebted to the accurate and graphic pencil of Sir John Herschel- shows one side of Mars. The darker parts are seas, and the land is characterized by a reddish color, undoubtedly springing from its chief geological formation. The bright spot at the top, is at the pole of Mars; it disappears as the Sun shines on it more directly, and there can be no doubt that it is a reflection from snow. Rain and sunshine are therefore there, mornings and gorgeous sunsets, with their tongue of flame shooting across the waters; also in Mars there is the eternal flow of the ocean! Its tides, however, must be gentle, such as wash the isles of Egean. The division of this planet into land and sea shows that its profile is irregular- in other words that there are elevations in it.

Nichol, J.P., The Phenomena and Order of the Solar System, 1843, Dayton & Newman, New York.

1843 - When viewed with a powerful telescope, the surface of Mars appears diversified with numerous varieties of light and shade. The region around the poles is marked by white spots, which vary their appearance with the changes of seasons in the planet. Hence Dr. Herschel conjectured that they were owing to ice and snow, which alternately accumulates and melts, according to the position of each pole with respect to the sun. It has been common to ascribe the ruddy light of this planet to an extensive and dense atmosphere, which was said to be distinctly indicated, by the gradual diminution of light observed in a star as it approached very near to the planet in undergoing an occultation; but more recent observations afford no such evidence of an atmosphere.

Olmstead, Dennison, An Introduction to Astronomy, 1843, Collins, Keese and Co., New York. - back to top

1859 - The extraordinary height and density of the atmosphere of Mars, are supposed to be the cause of the remarkable redness of its light. It has been found, by experiment, that when a beam of white light passes through any colorless transparent medium, its color inclines to red, in proportion to the density of the medium, and the space through which it has traveled. Thus the Sun, Moon, and stars appear of a reddish color when near the horizon, and every luminous object, seen through a mist, is of a ruddy hue.

Burritt, Elijah H., The Geography of the Heavens, 1859, Mason Brothers, New York. - back to top

1869 - To the naked eye Mars is the reddest star of the sky, shining with a steady brightness, which varies with its distance from the earth. In the telescope its color is less intense, and is relieved by spots of bluish-green or white. The red portions are thought to be land, showing the general color of rocks and soil; the green tints are believed to come from water. Definite outlines of lands and seas are discernible. Mr. Dawes has mapped them, and they have received the names of distinguished astronomers who have given special study to this planet. The long bottle-shaped seas, and the vast length of coastline contrast strongly with the broad oceans and compact continents on the earth.

Peabody, Selim H., The Elements of Astronomy, 1869, Wilson, Hinkle & Co., New York. - back to top

1870 - Then, lastly, there must be rivers on Mars. The clouds which often hide from our view the larger part of a Martian continent indicate a rainfall at least as considerable (in proportion) as that which we have on the earth. The water thus precipitated on the Martian continents can find its way no otherwise to the ocean than along river courses.

As to the nature of these rivers, again, we may form conjectures founded on trustworthy analogies. The mere existence of continents and oceans on Mars proves the action of forces of upheaval and of depression. There must be volcanic eruptions and earthquakes modelling and remodelling the crust of Mars. Thus there must be mountains and hills, valleys and ravines, water-sheds and water-courses. All the various kinds of scenery which make our earth so beautiful have their representatives in the ruddy planet.

Proctor, Richard A., Other Worlds Than Ours, 1870, Thomas Y. Crowell & Co., New York. - back to top

1879 - The first thing that strikes the observer is a dazzling spot of white near the pole which happens to be toward him, or at both poles when the planet is so situated that they can be seen. When the north pole is turned toward the sun the size of the spot sensibly diminishes, and the spot at the south pole enlarges, and vice versa. Clearly they are ice fields. Hence Mars has water, and air to carry it, and heat to melt ice.

This carrying of water from pole to pole, and melting of ice over such large areas, might give rise to uncomfortable currents in ocean and air; but very likely an inhabitant of earth might be transported to the surface of Mars, and be no more surprised at what he observed there than if he went to some point of the earth to him unknown. It may be conjectured that Mars might be a comfortable place of residence to beings like men.

Warren, Henry White, Recreations in Astronomy, 1879, Harper & Brothers, New York. - back to top

1890 - On the question as to the possibility of life on Mars, a few words may be added. If we could be certain of the existence of water on Mars, then one of the most fundamental conditions would be fulfilled, and even though the atmosphere on Mars had but few points of resemblance in composition or in density to the atmosphere of the earth, life might still be possible. Yet even if we could suppose that a man would find suitable nutriment for his body and suitable air for his respiration, it yet seems very doubtful whether he would be able to live. Owing to the small size of Mars and the smallness of its mass in comparison with the earth, the intensity of the gravitation on the surface of Mars would be very different to the gravitation on the surface of the earth. The effect of such changes on man would be indeed remarkable. He would experience a buoyancy quite unfamiliar to his terrestrial experience. It may well be doubted whether our organism would be adapted to a change so radical and so complete. We should imagine that the circulation of the blood and the various movements which constitute life would be deranged by such changes.

Ball, Robert Stawell, The Story of the Heavens, 1890, Cassell & Co., London. - back to top

1906 - That Mars is inhabited by beings of some sort or other we may consider as certain as it is uncertain what those beings may be.

Just as we have now found organic existence in abyssal depths of sea and in excessive degrees of both heat and cold, so do we find from exploration of our island mountains, which more than any other locality on earth facsimile the Martian surface, its possession there as well.

Another point, too, is worth consideration. In an aging world where the conditions of life have grown more difficult, mentality must characterize more and more its beings in order for them to survive, and would in consequence tend to be evolved. To find, therefore, upon Mars highly intelligent life is what the planet's state would lead one to expect.

By studying others we learn about ourselves, and though from the remote we learn less easily, we eventually learn the more.

Lowell, Percival, Mars and Its Canals, 1906, The Macmillan Co., New York. - back to top

1906 - It is the design of physical science not only to record but to explain appearances; and the canals, whether double or single, have, to many astronomers who have seen them, a look of artificiality rather than naturalness. If we accept the former, the explanation of the canals themselves, advanced by W. H. Pickering and reinforced by the argument of Lowell, seems very plausible: water is scarce on the planet; with melting of the polar caps, it is gradually conducted along narrow channels through the middle of the canals, thereby irrigating areas of great breadth which, with the advance of the season, become clothed with vegetation.

Of course, acceptance of this theory implies that Mars in ages past, has been, and may be still, peopled by intelligent beings; and that continuation of their existence upon                that planet, during secular dissipation of natural water supply, has rendered extensive irrigation a prime requisite. But only by long continued observation of the behavior of canal and oasis in both hemispheres of Mars can we hope for a rational solution of the question of life in another world than ours.

Todd, David, A New Astronomy, 1906, American Book Company, New York. - back to top

1926 - The explanation for the scanty atmosphere of this planet is that its mass is so small and its surface gravity so feeble that it has not power to control one. If Mars does control an atmosphere, probably it is made up largely of the heavier gases. When Mars passes between us and a star the light of the star is suddenly extinquished as the edge of Mars reaches it. If Mars had an extensive atmosphere the light of the star would gradually diminish as it shone through more and more of the gaseous envelope surrounding the planet. Probably atmospheric pressure on Mars does not exceed that on the top of our highest mountains.

The most serious question in the interpretation of the polar caps is that apparently the climate of Mars ought to be considerably colder than that of the earth. Mars is so much farther from the sun than the earth is, that it receives less than half as much light and heat from the sun as the earth. Using this fact to compute the theoretical temperature which it would have if its atmospheric conditions were the same as those of the earth, and assuming that the mean temperature of the whole earth is 60 degrees F., it turns out that the average temperature on Mars should be 38 degrees below zero F.

Moulton, Forest Ray, Astronomy, 1926, American School Publishers, London. - back to top

1926 - Finally, after all these conditions are satisfied, will life come or will it not. We must probably discard the at one time widely accepted view that once life had come into the  universe in any way whatsoever, it would rapidly spread from planet to planet and from one planetary system to another until the whole universe teemed with life; space now seems too cold, and planetary systems too far apart. Our terrestrial life must in all probability have originated on the earth itself. What we would like to know is whether  it originated as the result of still another amazing accident or succession of coincidences or whether it is the normal event for inanimate matter to produce life in due course, when the physical environment is suitable. We look to the biologist for the answer.

The astronomer might be able to give a partial answer if he could find evidence of life on Mars or some other planet, for we should then at least know that life had occurred more than once in the history of the universe, but so far no convincing evidence has been forthcoming. The supposed canals on Mars disappear when looked at through a really large telescope, and have not survived the test of being photographed. Seasonal changes necessarily occur on Mars as on the earth, and cerain phenomena accompany these which many astronomers are inclined to ascribe to the growth and decline of vegetation, although they may represent nothing more than rains watering the desert. There is no definite evidence of life, and certainly no evidence of conscious life, on Mars or indeed anywhere else in the universe.

Jeans, James, The Universe Around Us, 1929, The Macmillan Co., New York. - back to top

1932 - There is no longer any doubt as to the existence of the canals of Mars. They have been observed by many astronomers, and have been photographed successfully. In all probability they are somewhat broader, and less regular and artificial in appearance, than they seemed to some of the earlier observers. We accept the canals as natural features of the Martian landscape.

There appears to be life on the planet Mars. A few years ago this statement was commonly regarded as fantastic. Now it is commonly accepted. We refer, however, to forms resembling our vegetable life and not to intelligent human life, for there is no evidence to prove the existence of such life on Mars. The planet possesses air and     water, although in very small quantities compared with the earth, to be sure; and in the tropics the surface is above freezing at noon, although far below freezing most of the time even there and of course all the time on the rest of the planet.

Baker, Robert H., Simon Newcomb's Astronomy for Everybody, 1932, Garden City Publishing Co., Garden City, N.Y. - back to top

1935 - Astronomers at Mount Wilson inform us, as the result of their spectroscopic examinations of the planet, that the amount of oxygen above the reflecting level of Mars cannot exceed a thousandth part of the amount above an equal area of the earth at sea level, while the amount of water vapor is as low as five percent. These restrictions on life appear to be serious. The blue-green areas are not bodies of water. Mars is a desert, in general.

The dark markings in a Martian hemisphere grow greener and more prominent in the late spring and early summer of that hemisphere. They fade to a chocolate brown as the fall season approaches. These changes in the surface markings are such as would be expected, if they are produced by the growth and decline of vegetation. If this be the correct explanation, then there is life on Mars- vegetable life, at least. But some other explanation of the seasonal changes may come forth. It seems wisest to leave the whole question of life on Mars open for the present.

Baker, Robert H., An Introduction to Astronomy, 1935, D. Van Nostrand Co., New York. - back to top

1935 - Some people are of the opinion that the markings on Mars are canals which have been constructed by intelligent human beings. There seems to be no good reason why human beings could not live on Mars. This planet is probably at a rather advanced period in its evolution and much of its surface is desert waste. We would probably find on Mars a higher state of civilization than on the earth, but the inhabitants, like the planet, have probably passed their zenith and are on the decline.

The question is frequently raised as to whether it will ever be possible to send signals to Mars. How much power will be required? Can the millions of horsepower of energy which is exhibited in lightning be seen on Mars? Is radio communication possible? Who is going to pay the cost of this gigantic power plant? What language are we going to speak? What are we going to talk about? Do the inhabitants of Mars know anything that we know, that is, can we find a topic of conversation? How are we going to determine whether or not they get our message?

Harding, Arthur M., Astronomy, 1935, Garden City Publishing Co., Garden City, N.Y. - back to top

1944 - Many observers of Mars deny the existence of this network of fine straight lines, claiming that the markings are not only much broader individually but that there are considerable variations in width and direction. There are on the surface of Mars many details which cannot be seen individually but which the eye unconsciously integrates into lines and spots. If this is the case we would expect small telescopes to bring out the fine network while large telescopes, having a greater resolving power, would be able to bring out more detail and thus destroy the appearance of the network.

There seems to be no question about the existence of some sort of vegetation on Mars. Change in the color of the dark regions with the change in seasons appears well established, but we have no way of determining whether this vegetation consists of the simple forms, such as might correspond to lichens and mosses on the earth, or of higher forms, such as trees. If plant life exists it does not seem impossible that at least low forms of animal life also may be there, but no observations have been brought forward to establish this.

Fath, Edward Arthur, The Elements of Astronomy, 1944, McGraw-Hill Book Co., New York. - back to top

1949 - It has often been suggested that the bright regions of Mars may resemble the "Painted Desert" and that its surface is covered with reddish iron oxides, in particular FE2O3; that, in fact, the oxygen of the Mars atmosphere was depleted in the process of oxidation. The reflections of red soil and red rock, collected by the writer in Oklahoma, Texas, and       Arizona, were found to be quite different from those of Mars. However, a brownish, fine-grained felsite was found that closely matches the Mars curve in the full range considered. We may tentatively assume that the bright desert regions of Mars are composed of igneous rock, similar to felsite.

The Mars atmosphere contains, therefore, slightly more than 2.2 as much CO2 as the atmosphere above McDonald Observatory. Mars polar caps are not composed of CO2 and are almost certainly composed of H2O frost at low temperature.

It is too early to conclude that the green areas on Mars are covered with lichens or mosses; different forms of plant life may well have developed under very different conditions on Mars.

Kuiper, Gerard P., The Atmospheres of the Earth and Planets, 1949, University of Chicago Press, Chicago, Ill. - back to top

1949 - Then the pendulum swung back. It was all a mistake. The canals were optical illusions, caused by eyestrain and by the effort to see details below the limits of visibility. Those color changes, and especially those reported by Percival Lowell from his Flagstaff Observatory built especially for the purpose of establishing the Martians were mere wishful thinking. The dark areas were not seas but something like the Asiatic salt steppes, only much saltier, too salty for anything to grow. And even the white polar caps which were to have furnished the irrigation water were not water at all but frozen carbon dioxide- not ice, but dry ice.

Suppose all these dismal statements were correct (which they are not), Mars would have remained a highly interesting planet. But after all the imaginative tracing of Martian superengineering, the disappointment, especially to the layman, was enormous.

The present concepts of Mars: There are no real mountains on Mars. The polar caps are water, or rather, ice. We are justified in believing in life on Mars- hardy plant life. And as of 1949, the canals of Mars do exist.

Ley, Willy, The Conquest of Space, 1949, The Viking Press, New York. - back to top

1950 - As we look in on another world and try to understand what is occuring there we see in the generally reddish surface a desert where nothing flourishes. The white polar caps are rather thin snow fields. The seas and fine dark markings may well be depressions which catch enough water to promote the growth of some hardy types of vegetation.

The times of the Martian year when the dark markings change in intensity and color are such as would be expected if the changes are caused by the growth and decline of vegetation. This seems to be true of the canals as well. Kuiper's studies of sunlight reflected from the green areas seem to rule out familiar seed plants and ferns. They suggest but do not definitely establish the presence of lichens and certain hardy mosses.

The hazy atmosphere of Mars itself affects the view of the planet's surface. Kuiper's observations at McDonald Observatory lead him to suppose that the haze is caused by ice crystals in the atmosphere of the planet, similar to the light cirrus clouds in our own atmosphere. At times the haze clears rapidly over a large area of the planet.

Baker, Robert H., Astronomy, 1950, D. Van Nostrand Co., New York. - back to top

1953 - Carbon dioxide has not been detected in the Martian atmosphere. This is not surprising because carbon dioxide must be present in large quantity before it will produce absorptions of sufficient strength to be detected.

As we have mentioned, the color of the surface of Mars provides sure evidence of the presence of free oxygen, at any rate in the past. The presence of free oxygen almost certainly demands the existence of vegetation. Combining this argument with the evidence from the changes that occur on the surface, we may conclude that it is almost certain that there is some form of vegetation on Mars. If this conclusion is accepted, it follows that life does not occur as the result of a special act of creation or because of some unique accident, but that it is the result of the occurrence of definite processes; given suitable conditions, these processes will inevitably lead to the development of life.

Jones, H. Spencer, Life on Other Worlds, 1953, The New American Library, New York. - back to top

1955 - Kuiper considers the rocks are composed of igneous rock, similar to felsite; but H. Spencer Jones suggests that the distinctly ruddy tint is due to the "oxidation of iron-bearing ores by atmospheric oxygen". So we probably do not greatly err in believing that the reddish-ochre stretches which give the planet its distinctive color consist of sandy desert alternating with rusty rocks. The low reflective capacity of the planet, which sends back only 15 percent of the light which it receives confirms this supposition. The desert regions appear to be about two thousand feet above the level of the lower areas and to consist of plateaux, diversified by valleys and crevices but comparatively flat. There are no ranges of mountians on the planet nor even high hills.

Macpherson, Hector, Guide to the Stars, 1955, Philosophical Library, New York. - back to top

1964 - The conspicuous red color apparently comes from regions not too different from various deserts of the earth, such as the Painted Desert of Arizona. White "buttons" on the two polar caps, which vary in size with Martian seasons, are undoubtedly formed from ice- presumably a thin layer of hoarfrost- which completely vanishes during the Martian summer. Water is a scarce commodity; the planet possesses no discernible oceans or lakes. The grayish areas, once thought to be water, show seasonal changes suggestive of vegetation, but their precise nature has not yet been determined. They may be a form of moss or lichen.

Menzel, Donald H. , A Field Guide to the Stars and Planets, 1964, Houghton Mifflin Co., Boston. - back to top

1976 - (Tom Mutch, speaking about the Mariner spacecraft discoveries that there were no oceans, no canals, no vegetation on Mars)

To a geologist, each day's pictures were like a new traverse across unfamiliar terrain. Progressively revealed as a new planet, detail emerging from obscurity with overwhelming rapidity. Immense fracture systems spread across the planet as a new geologic map was constructed. Near the telescopic feature, Argyre, a basin the size of the lunar Imbrium Basin was identified. Hellas, whose western margin was seen in pictures taken by the Mariner '69 mission was revealed in its entirety. Strange tributaries and fluvial-like forms were seen scattered across the equatorial region. Sinuous ridges resembling lunar mare ridges were seen. Lobate flow fronts suggesting basaltic outpouring were observed. The new pictures quickly erased from memory the "old" Mars as though the countless hours of previous speculation had been little more than science fiction.

Mutch, Thomas A. et al, The Geology of Mars, 1976, Princeton University Press, Princeton, N.J. - back to top

1980 - As telescopes improved and the equipment used with them grew more sophisticated, the image of Mars began to change. The first challenges came from a series of temperature measurements. Mars is cold. The average temperature on Mars falls far below the freezing point of water. Under these conditions, any channels of liquid water, natural or Martian made, appear highly unlikely.

By the early 1960's, astronomers knew that Martian "air" consists mostly of carbon dioxide, with only a trace of water vapor. The total amount of gas in the Martian atmosphere, and the pressure that the atmosphere exerts at the Martian surface, must be less than one percent of the values for our atmosphere. The surface pressure plays an important role in the speculation about the possible existence of life on Mars, because if the Martian atmosphere does not exert at least 0.6 percent of our atmosphere's pressure, then water cannot exist as a liquid, no matter what the surface temperature may be. Without liquid water, life as we know it cannot exist.

Goldsmith, Donald and Owen, Tobias, The Search for Life in the Universe, 1980, Benjamin Cummings Publishing Co., Menlo Park, Ca. - back to top

1996 -The Mariner 4 results spurred astronomers to completely revise their ideas about Mars; it was now obvious that earlier views had been very wide of the mark indeed. The vegetation theory was dead- the Martian environment seemed to be too hostile to support vegetation, and even the existence of the wave of darkening, which "took second place only to the Martian canals in historical development of the life on Mars hypothesis" was doubtful. Though there could be no question that there were considerable changes in the form and intensity of the dark areas, the existence of an actual "wave" extending from the south pole to the equator each spring seemed at best only weakly supported by the observations. A study by Charles Capen of the Lowell Observatory showed systematic latitudinal changes in the intensity of features with the seasons, at least, did not seem to occur, and any changes that did take place were evidently due to windblown dust rather than vegetation. Carl Sagan describes this as "the alternate deposition and deflation of windblown dust having detectable contrast with respect to basement material".

Sheehan, William, The Planet Mars, 1996, The University of Arizona Press, Tucson. - back to top

CONCLUSION: IT'S DUST, BLOWIN IN THE WIND, MESSIN WITH OUR MINDS