The markings on Mars are roughly constant but do change from year to year. There is, as E.C. Slipher termed it, an additional "secular" amount of change that is more local in time and region. At its closest approach to Earth, Mars is 26 arcseconds in diameter and has the Southern Hemisphere turned towards the Earth. As one telescopically observes Mars, the interrelationship of Mars' rotation and Earth's rotation results in surface features noticeably shifting as a whole after 4 days. After 40 days, they are back where they started. Exact reproduction of the position of surface features occurs once every 15 years.

At favorable and unfavorable positions of Mars relative to Earth, at times of the year very varied, and with diverse instrumentation and observers, there appeared a class of features that DeVaucouleurs declared to be an irritating enigma. He was referring to the canals of Mars. They partake of a notion that there could have been Martians, godlike, in old realms of imagination furthering the mythic fantastic possibilities of comparatively superior, and better, civilizations than our own.

The basis for the belief in these Martians lies with the canals. They, in turn, are dependent on drawings made by astronomers from another era. Beer and Madler in 1830-1832 drew Mars as having wispy lines. They were using a 3 3/4-inch refractor. Proctor drew Mars as having thick channels. Dawes in 1864-1865, at a time when Mars was favorably placed for Earthly viewing, also drew wisps, and streaks for some markings of Mars. Nathaniel Green, using a 13-inch reflector, and Webb also drew Mars somewhat similar to Proctor.

As late as 1961, E.C. Slipher stated flatly that the Martian canals existed. According to Slipher, all skilled observers who go to the best available sites with the best available telescopes did not fail to see the canals. He called them the wonderful network of canals. This is a key point, noted many years earlier, that a few canals, wisps or streaks, however ill-defined or in the reverse, are nothing more than a curiosity of planetary observation; but to put these interrelated canals into a network - then you had a fixation, a realization that these canals, by being connected, represented activity. The canals were made. A network meant design. By whom? For what?

In some respects, the Martians, who built the canals, were in our image in that the canals provided pathways for the flowing of fluid, presumably water, to regions of Mars having need of an augmented water supply. They were for irrigation to Martian regions drier than the Martians had wanted them to be.

E.C. Slipher, in 1961, showed photographs of the canals. Unfortunately, he said, the original photographic plates showed the canals as well as could be seen visually but these photos did not reproduce well for publication. Approximately 50 years before, Percival Lowell had also said his photographs of Mars showed the canals but the tiny images of Mars containing these canals did not show up well in the popular magazines in which they then appeared.

As is well known, Lowell was the ardent champion of the existence of the canals of Mars, the Martians, their network of waterways, and their technological and other superiority to us. Even so, he did not discover these wondrous canals. Lowell took his cue for the existence of the canals from Schiaparelli. It was Secchi in 1869 who drew channels (canali) on Mars. In 1877 Schiaparelli drew what others had seen as much narrower and linear. They would become stark stalks. In 1877 he was using an 8 1/4-inch refractor. He would later use a larger telescope. He said he glimpsed a vast, intricate network of fine lines criss-crossing Mars. He drew them despite their form often being vague. Sometimes he saw them as clear and concise. Either as clear or vague, for him they were not broad channels but finer and, above all, systematic and not varying in their arrangement. Not varying, that is, until 1879 when, during the Martian spring he began to see doubles. Where once there had been one lonely canal traversing hundreds or thousands of miles, there was now a partner, matching mile for mile the original one and with a constant spacing from that original. It became not a few doubles here and there but many of them.

Prior to 1879, Schiaparelli's map from 1877 showed not anything that can be truly designated a canal. There were no numerous lines or fine stripes he later found in such abundance. Then any less than prominent Martian markings appearing as a streak became a canal. Early on, the canals usually showed themselves only one or two at a time. These showings were only in glimpses, a snatch of clarity only very briefly and not very often in long observing sessions. He found the canals on a fine clear night in Italy. It was the first time he had used that telescope.

Lowell, in 1894 in Arizona, at first doubted he was seeing the canals with his 18-inch refractor. As he gained experience in sighting them in very brief periods of good seeing, he saw more and more canals. He would see new canals, canals never before seen and go on to outdo Schiaparelli. Lowell was seeing the canals also during his first use of his telescope. This was during the favorable opposition that commenced October 13, 1894. He was present in an opening in the woods on a low mesa, close to the west side of a town of 800, Flagstaff. With his keen eyesight and the realization that a whole new instrument, the air, the good air, could be put into use for planetary observation, Lowell and associates saw 183 canals during that 1894-95 opposition. The Martian April came in our June. Martian August was our November. The Red Planet's vernal equinox was April 7, 1894. The summer solstice came August 31. One degree on the Martian surface was 37 miles. Through the degrees from the poles to the equatorial regions, Lowell saw, as others before him had seen, the seasonal darkening of features. Some markings would always get darker in the Martian spring and fade in the Martian autumn. The canals participated in this wave of darkening, the dark advancing from pole to equator.

A tumult in astronomy had also advanced. It went into the beginning of the 20th century and peaked in 1907. The tumult was the Mars furor. Lowell was at the center of it. Others had decreed there were no canals on Mars. No Martians were there as canal builders. No water was at the poles to be brought to the equatorial regions by those spindly-looking canals. Lowell said otherwise - canals, Martians, and their civilization all in one breathtaking sweep of assertion. For him astronomy was an interest and a mood. He exuded Darwinism, pragmatism, romanticism, and an imagination, Baconian, as method.

He could discern canals on Mars. Barnard, with a 36-inch refractor, saw much detail, but found no canals. Charles Burton in 1869 using the Rosse reflector noted the most remarkable of many details were black very small points distributed abundantly in one region of Mars. No canals. Hale in 1909 using the 60-inch Mt. Wilson telescope stopped down to 44 inches saw much bewildering intricate detail but no canals. Gaston Millochau, in 1899-1903, using the great Meudon refractor of 32 3/4 inches, saw much irregular detail on the surface of Mars. No canals. Cerulli in 1897 with a 15 1/2-inch refractor found some well known canals, like Lethes, when viewed under perfect seeing conditions, lost the status of a line and became a complex system of very small spots. Antoniadi had superb seeing for the Meudon refractor on his first night. He observed Mars then. There was too much detail to be drawn. No canals. In 1924,at the best opposition of the 20th century, observers at Flagstaff, upholding the Lowellian tradition, saw the canals. Trumpler, also in 1924, using the Lick 36-inch refractor drew a great many canals. Charles Young with a 23-inch refractor never saw the canals as Schiaparelli had drawn them, nor did Keeler at Lick.

Antoniadi sent drawings of Mars to Lowell. Antoniadi had used the Meudon refractor. Lowell thought the best one (which showed canals) as the one Antoniadi had marked as being done when the air only permitted tremulous definition. In those drawings during much much better seeing the canals were not to be found. E.B. Frost was asked if the mighty Yerkes (40 inches) refractor could reveal the canals. Frost - "Yerkes telescope too powerful for canals."

Frost was right. Lowell had argued that telescopes of smaller aperture were best for sighting the canals. Not too small of course but at least Lowell's 18-inch refractor served the purpose. Schiaparelli started his observations of the canals with an 8 3/4-inch refractor. Schiaparelli seems to be a special case. All other consistent reputable reports of canals involved larger apertures. Going well beyond Lowell's 18-inch up to 60 inches in aperture did not help to discern the canals. Optically speaking, bigger is better when the atmosphere allows for it. Lowell, after the 1894-95 opposition used a 24-inch refractor but he usually reduced the effective aperture to 18 inches or less with a diaphragm.

So the canals have a correlation to aperture. Also, with the larger apertures, where those canals were to be seen would have spots, splotches, and dots taking up that space. Only in poor seeing, according to Antoniadi, could he, and by implication, could others, see the canals. Antoniadi also, among others, noted that the canals lacked perspective. They went across the globe of Mars for great lengths and should have assumed the character of great arcs of circles. They did not. This could be because what the observers discerned as giving opportunity for the canals were not on the surface of Mars.

Cerulli from July 1896 to February 1897 saw some canals easily in July when Mars was 7 arcseconds. Later, in December, when Mars was 17 arcseconds, the same canals were the same size. Schiaparelli did it in the reverse on an occasion. For him, when Mars was 21 arcseconds he saw no canals but one in a region of Mars. Later, after the angular size of Mars had gone to 5.7 arcseconds, he then saw canals in that region. Both these cases can be perhaps explained by having that which lends itself to canal formation as being quite small.

This minute facilitator would also need to participate in the wave of darkening that comes with the Martian spring. The canals have always been a part of the wave of darkening. McLaughlin in 1954 thought that albedo changes, as he termed it, could result from wind action with volcanism to supply dust deposits. Sagan thought that wind-blown dust could be the cause of the wave of darkening.

The Martian wind on a global scale is estimated, on average, to have a velocity at night on flat terrain of 2 meters (m)/second (s). At noon on the flats it is 6 to 8 m/s. Near mountains the velocity can be as much as 20 m/s. Certain storms to which Mars is subject, can produce wind velocities of 50 m/s. The polar areas can endure a velocity around 100 m/s.

Dust can rise to 40 km above the Martian surface. Large dune fields exist on Mars. One dune in particular is reputed to be largest in the Solar System. The planet is nearly always seen through a dusty veil. Martian dust plumes are huge. They can be 20 km long and 1 km high. There are local, regional, and global dust storms. Lowell thought the Martian atmosphere was placid. He observed in an era when the vast dust storms to which Mars is subject were unknown.

Another outstanding class of features of Mars is its craters. There are more craters in the Southern Hemisphere than in the Northern Hemisphere. Most observers have found more canals in the Southern Hemisphere. The Viking and Mariner spacecraft revealed about 170 large Martian craters, mostly greater than 62 miles in diameter, and 6,000 smaller craters.

Could one see the craters, any craters, from Earthbound telescopes? If one has perfect seeing, a rather rare commodity, a fairly accepted measure of resolving power of a telescope is Dawes Limit or 4.56 arcseconds divided by the aperture in inches. This is a relationship that was derived empirically by Dawes in finding what aperture among smaller refractors could separate double stars. Experienced planetary observers know that this limit does not strongly pertain to extended objects such as planets as opposed to point sources like stars. The experienced argue that the limit for planetary viewing can be bettered by 2 to 14 times more acutely. Beyond these matters of opinion, it has been found that the Hubble Space Telescope (HST) is capable of revealing craters on Mars. The HST has an aperture of 94.5 inches, its planetary camera at f/30 has an angular resolution of 0.043 arcseconds. The HST has no dense earthly atmosphere to hinder its work and can get close to theoretical limits for resolution. If one accepts Dawes Limit, then the HST should be able to see objects on Mars with a diameter of about 8.1 miles at a favorable opposition of Mars. During 2001 the HST had a look at Mars on one occasion. More than a few craters could be recognized in the image it secured.

But then Lowell and the rest had nothing like the HST available to them. Did they ever see craters on Mars? The consensus is that they did not. Given that, could Lowell have been aware of craters on Mars? I believe there is a possibility that he may have done so. I propose that the canals of Mars are a function, like a mathematical function but not as precise, of the presence of Martian dust aloft over craters on Mars. The existence of the canals has always been found at the very limits of visibility. One needs the best eye, the best sky, and the best telescope. One more factor is required and that is the ability to discern the canals. I don't believe one can say the ability to "see", no, more to discern. To realize the craters, to put them into existence, Lowell could have seen Martian dust framed against a backdrop of craters. It was somewhat like the Rorschach tests where patterns can be found and usually those patterns are rather routine except among the more imaginative persons.

Once one canal or two became fixed, then the orientation of the remaining community of connecting canals then became determined. If not, one had a mass of perceptions unorganized and "wasted" (if the observer was so disposed to regard the fleeting imagery) and so to "make use" of the discernment then the rest of the canals could not assume independent orientation. A network sprang up. Once known, then in the future any part of the canalic artwork reestablished itself and the rest followed as seen before.

If the background crater was too large or the aperture of the telescope was too large, then the dust had nothing for orientation supplied by the observer, to "direct" it, to "frame" it, as it were. The canal would not form; it would smear out into spots or splotches. If the crater or aperture were too small, then not sufficient supportive function would be present. Only an intermediate range of size of craters and telescope would serve the purpose. How many craters would be needed per canal? I presume this could vary. Certainly the anchors of the network would have many craters determining the canal. But in other instances it might take only two points, a start and a finish, two craters to determine a line, a canal. Lowell may have not used the same craters as an aid in discerning certain canals. The dust might have been over other closely adjacent craters. His plates showing the canals as they appear in his book, Mars, are for the 1894-95 observations. They are yet more like streaks and more indistinct than they would later become. Further association by him with his creation made for him, as for Schiaparelli, more definitive characterization of what they thought should be seen.

There was a boundary between the seen and the discerned. Most crossed the boundary willy-nilly and at will found what could only be discerned as that which they had seen. Maunder had seen sunspots much smaller than a single sunspot if the sunspots made for a linear composition or nearly so. A somewhat similar formation of canals could have taken place. Nevertheless, the canals were not a mere summing up of roughly aligned features too small to be individually distinguished. The craters were never seen. Lowell misspoke when he said the saw canals, at best, he discerned them. In sparsely cratered areas, he could have used fewer craters to have the line for the canal. It is possible that features other than craters could have contributed to the existence of the canal. Even so, the craters are the prevalent surface features that could have aided in canal discernment. Other features are too few as a class of object and, on the whole, too often dispersed. In any event, the canals could traverse sparsely populated cratered areas.

Here and there Lowell saw an oasis on Mars. This was a place where more than one canal seemed to run into a junction. It could have been that an oasis was not from whence a canal originated but rather was where canals met. Given some differing starting angles for the canals, some would intersect and the underlying topography could, at places, favor apparent termini. The canals did not issue from the oasis; however, it is rather that they met there.

As for the famous or infamous double canals, I propose that those doubled canals were there when additional dust was in the area of a suitably sized group of craters. Should there be more dust, but in the area of too large a crater or too small a crater, no double. Those craters that could support doubles had to be of a certain size range. If all the necessary craters could be classed in the nearly same size range, then a double, the secondary, would parallel the original, the primary, canal for the duration of the course of the primary. Again, if one crater at the start of a canal and one at the finish were large enough in the presence of increased dust, a double could be realized. The sizes for the defining craters would determine the spacing of the doubles apart from each other. New canals, double or not, could pop up when sufficient dust for sufficient duration newly entered an area seen previously by Lowell.

Have I too raised sufficient dust for a suitable duration and built up a network of reasoning ever as much lacking in reality as Lowell? There are ways to test the reasoning. In 2003 Mars will present a very favorable opposition. Lowell's telescope still stands in Flagstaff. Also, at any desired remove from Flagstaff could be constructed a representation of the cratered Martian surface, properly illuminated, and with dust before one's eyes. Perhaps one could drop red or at least dark food coloring into an aquarium, in front of "Mars" and look through the watery atmosphere for canals to form. More elaborate and more realistic conditions could be generated for such in-lab tests. As for a luney idea, one could try to find lunar canals. Long ago Beer and Madler found streaks on the Moon that upon closer examination were actually strings of little craters. One need not be restricted to recreating their finding. Certainly there are enough craters on the moon. The dust is another matter. One might hunt for lunar canals by, perversely, observing the Moon on cloudy nights. The brightness of the Moon may necessitate daytime viewing or employing color filters or a polarizer. Probably the best optical instruments for use with the Moon in this regard would be binoculars or spyglasses.

However one goes about finding Martian or other canals now at this late date, one must remember an important other requirement. One must be able to "see" them. One must be receptive to an awareness of their existence. Beware, these canals partake of gods, demons, and fabulous creatures. You are entering a zone at the limits of visibility where the psychological, religious, and philosophical can storm upon you at full gallop. Hold tight to your preconceptions, modify them much by hope and little by fear. Alone, one night, soon, if you dare, with the God of War, the Red Planet mysteriously comes into your ken. Have faith, Mars and its canals still exist.

Look for them especially after storms on Mars. Some artistry is required. The marvelous excitement of another form of highly developed life is still there. They are intelligent and smarter, super though not superhuman. Grasp an eyepiece, put it in your wayback machine and become a traveler in time to a great era in human time. To a time when science still had much humanity. Fanciful it was, rich in ideas, ripe with possibilities, positively glowing with them. An awesome potential then in more respectable and more courteous surroundings. So many then could be so much in contact in that society's consciousness, talked of, thought about, very close to real. As close as it gets without getting there. Straining the scientific resources to confirm the craftsmanship of the astronomical instruments of the day. Blend in scientific imagination of the planetary observers and know the new, wondrous personal view tempered by societal strictures there in the dark backyard, the basement lab, or in the reading room.

You will never see the craters, they are beyond seeing; but they can be briefly known indirectly. Lower the Dawes Limit. Survey areas of Mars such as the Vastitas Borealis, Elysium Mons, Hesperia Planum, Terra Cimmeria, Valles Marineris, and the Amazonis Planitia. These certainly are real. Spacecraft in orbit about Mars have shown them quite well. But ultimately you are not going for objectivity here. You and Mars. The canals. Have at it.