Exploration of Mars and Schiaparelli's canals episode


It could be asserted that Mars is currently the main target in planetary exploration. More than 40 missions have been sent to explore our neighbour planet since the early sixties (half of which have failed), and up to six more are scheduled for launch within the next six years, having turned Mars into the most explored celestial body besides Earth.
Nevertheless, there were times when Mars was probably more popular among the general public than it is nowadays, and it was in a good measure because of the observations performed by the Italian astronomer Giovanni Virginio Schiaparelli during the 7 oppositions of Mars between 1877 and 1890. Here we review the history of the observations of the canali performed by Schiparelli and others, their controversial interpretations, and relate them with our current knowledge of the Mars environment provided by modern rover and satellites exploring Mars.

SCHIAPARELLI'S CANALI: BETWEEN MYTH AND REALITY

Giovanni Virginio Schiaparelli

Giovanni V. Schiaparelli (1835-1910) educated as an engineer and architect in the first place, but since his vocation being astronomy, he decided to start studying the subject at the University of Turin only to complete it within two years at the Berlin Observatory (1857-1858) under the direction of Johan Encke (1791-1865), one of the best astronomers of the epoch. Then, he spent a year working at the Pulkovo Observatory, San Petersburg, under the direction of Friedrich Georg Wilhelm von Struve (1793-1864), a specialist in the observation of binary stars. In 1860 he returned to Italy as the second astronomer at the Astronomic Observatory of Brera, Milan, becoming its director two years later.
During his long career (he resigned in 1900 due to sight deterioration), he proved to be a prolific and competent astronomer: he resolved more than eleven thousand binary stars, and discovered the asteroid 69 Hesperia. Through long and accurate observations, he could establish the relation of the meteor showers called Perseids and Leonids with the orbit of comets, advancing the theory, which afterwards was found to be correct, that meteor showers are caused by loose debris from comets. He performed as well measurements of the rotation period of Venus and Mercury, although on that occasion with incorrect results. Regarding Venus, Schiaparelli stated that its rotation period was between six and nine months, probably equalling its translation period, and as for Mercury, he calculated a rotation period of 88 days, far from the real value of 58.65 days. In order to have obtained the real value he would have needed making observations during more than seven years given the orbital and rotational features of Mercury, which neither Schiaparelli nor any other astronomer at the time managed to do. Indeed, both Venus and Mercury rotation periods were finally established in the 1960’s by means of the technique of radioastronomy. In addition, Schiaparelli was as well a prominent scientific historian, having realised for the first time that the celestial concentric spheres proposed by ancient authors such as Eudoxus of Cnidus (c. 395–390 BC- c. 342–337 BC) and Callippus of Cyzicus, (370 BC – 300 BC) unlike those described by later astronomers, were not conceived as material objects, but as a description of physical processes.
For all these achievements Schiaparelli received several awards becoming widely recognised within the astronomical sphere. He got the Gold medal of the Italian Society of the XL (40), the Lalande Prize of the French Academy of Sciences (twice, in 1867 and 1890), the Gold Medal of the German Academy, the Gold Medal of the Royal Astronomical Society and the Bruce Gold Medal of the Astronomical Society of the Pacific, and his sight keenness and the accuracy of their observations were highly appreciated.
In spite all these observational achievements, Schiaparelli became famous among the general public for another reason: his observations of Mars. In 1877, an opposition of Mars with respect to the Earth took place, that is to say, they reached the point of their closest approach along their respective orbits, which in this case occurs every 780 days, and Schiaparelli decided to take advantage of the occasion to observe the Red Planet. By that time, he had achieved to install a new telescope in the Observatory, which had started to be used for regular observations in 1875 after a period of testing and calibration. It was a refractor telescope built by the German maker Merz that meant a great improvement with respect to the instruments available in the observatory until then. It had a 218 mm lens with a focal length of 3.15 m, and the body was made of fir and mahogany in an equatorial mount moved by a counterweight mechanism. Its optical quality was quite high, having an effective resolution very close to the theoretical one according to the Rayleigh criterion, and it had 3 micrometers, two of them filars and the other annular, and 13 eyepieces, 7 positive with magnification between 8 and 690, and 6 negative with magnification between 67 and 468. It was an excellent instrument for performing micrometric measurements such as those required to resolve binary stars, the main use it was built for.

Figure 1. Merz refractor at Brera Observatory, Milan.
With this 22 cm aperture telescope Schiaparelli performed
most of his observations of Mars, describing his famous
canali for the first time.

So, in 1877, Schiaparelli started a systematic series of observations of Mars with the initial aim of testing the Merz telescope for the study of planetary surfaces and to draw his own map for the sake of comparing it with those available at that moment. Taking advantage or the micrometric accuracy of the telescope and applying his mastery, he determined the position of sixty two points to which he referred his observations of the planet, achieving to complete a remarkable new map far better than any other until then. Indeed, the huge amount of new features he saw made it necessary to implement a whole new nomenclature to substitute that by Richard A. Proctor (1837-1888) which was the most widely used at that time, despite his first intention of maintaining the same names. Those first observations were reflected in the article Osservazioni astronomiche e fisiche sull’asse di rotazione e sulla topografia del pianeta Marte, published in Rome in 1878.. In those observations Schiaparelli started to appreciate the famous canals (canali). He saw them as natural linear features of which he only could observe one or two at a time, never as the network he described later after several periods of observation.
These canals were the starting point of the further Mars mania, a delirious spiral of speculations that led to the semi-scientific conviction that Mars was inhabited by a developed civilization, which spread widely among the public fed by the huge amount of different kind of literature that was published on the topic. Schiaparelli himself was swept along by this tide, and wrote three articles about the matter in the magazine Natura ed Arte (in 1893, 1895 and 1909), compiled afterward in the book La vita sul pianeta Marte, in which, although keeping a certain prudence, he admitted the possibility that the canals he described had been built by “technical” creatures. While at first he advise that “it is not necessary to suppose the work of intelligent beings…” regarding the origin of the canals, little by little he showed himself more and more prone to admit that “…these canals constitute probably the main mechanism by which the water (and with it organic life) can spread over the dry surface of the planet”. He even asserted that the possibility they were the work of intelligent beings “includes nothing impossible”; indeed, he allows himself to imagine crops managed by agronomists, and even to speculate about the most likely form of government the martian society could have. With no doubt, he was influenced by the enthusiasm of Percival Lowell, an American astronomer who developed Schiaparelli’s descriptions of the canals triggering the said Mars mania.

Figure 2. First map drawn by Schiaparelli as a result of the observations performed during the 1877 opposition. The canals already appeared in this map, though not as well define as they became in further observations.

Mars oposition in 1879

In 1879, he was able to get 114 points of reference for his micrometric measurements. Along that series of observations, Schiaparelli found some shocking changes in some of the canals he observed the first time. They seemed to have divided into two parallel ones, and were drawn as finer and more defined lines than they were in the previous observations. He concluded that new canals had appeared in a process he called “gemination”.
By the time, the matter of the canals had started to be controversial. Nathaniel Everett Green (1823-1899), an amateur astronomer and painter had been observing Mars as well during the 1877 opposition from Madeira.

Figure 3. Map drawn by Nathaniel Everett Green during the 1877 opposition observations from Madeira. As can be seen, there is no trace of any sort of “canal” in it.

He had used a reflector telescope with a 33 cm lens and had drawn a map of its surface as well. He was observing the 1879 opposition from London, using a French refractor telescope with an 11 cm lens, when he was contacted by Schiaparelli who wanted to know his opinion about the canals. Green thought that Schiaparelli had represented some sharp features as canals where he only could see diffuse changing tones, and was convinced that Schiaparelli had not been faithful to observations, being the first who pointed out that the canals were nothing more than artefacts, wether they resulted from imagination or from the mere lack of drawing skills of Schiaparelli (Green himself was a renowned landscape painter). Proctor, for his side, wished that a skilful draftsman would have reflected the image on the telescope, not giving much credit, with relation to his own observations and experience, to what was reflected in Schiaparelli’s map. It is important to point out that, as Schiaparelli himself clarified, the canals did not appear as a distinct and clear feature in the eyepiece, and their description was a result of a gradual process of interpretation of the different and diffuse tones, shadows, and bright areas he could see. On the other hand, Schiaparelli’s sight had some remarkable defects or, not to be unfair, features, that must be taken into account to understand their aerographic[1] descriptions: he was myopic as well as colour-blind. This latter anomaly in the vision of certain colours use to be associated to a higher sensitivity to contrast with respect to a “normal” vision, what probably determined both the micrometric accuracy of their observations and his tendency to interpret as sharp lines what others observers saw just as diffuse shades. So in summary, it can be concluded that their drawings were not yielded from a direct and immediate observation, but they were rather a result of an elaboration process which was constrained by his particular vision.
Indeed, no other astronomer was able, at first, to observe the canals, but Schiaparelli being a prominent one, and since he insisted in the description of these features with increasing clarity, it became a challenge for many colleagues to see them, and little by little, the inability to do it began to be considered as a measurement of the inexperience of the observer. So the number of those who claimed to have seen the canals increased, overcoming the initial scepticism.

Mars oposition in 1881

During the opposition of 1881, and despite the fact that the size of Mars in the sky was only 16 seconds of arc (by comparison, in 1877 it was 25” and 20” in 1879) Schiaparelli claimed to have obtained excellent views of the planet, finding that the geminations had been extremely profuse. Along his observations he registered up to twenty of them in a month, which by the time being, he attributed to seasonal processes on the surface. At this time the vision of Schiaparelli established somehow the way Mars observations should be interpreted, and his illusion became an unquestionable fact. This way, some observers such as F. Terby looked for the canals Schiaparelli “had proved” to exist, checking his observations with the maps he had made. So his observations were strongly constrained by a previous idea and aimed to confirm information that was considered a fixed truth.

Figure 4. Map correspondent to the 1881 opposition. The canals have become more defined, and many of them have undergone “geminations”, appearing as two parallel lines.

The martian canals paranoia kept on growing since then. In 1886 Schiaparelli managed to install a new telescope at Brera, a Repsold-Merz 49 cm lens refractor, more powerful than the 22 cm Merz but optically inferior, with which he observed more and more geminations during the subsequent oppositions, and other observer such as Henri Perrotin (1845-1904) found new canals by using a 76 cm refractor at Nice Observatory.

Mars oposition in 1890

During the opposition of 1890 the craziness about Mars had exploded overflowing the scientific sphere, within which it was already outrageous enough, and the discovery of two bright projections (which were nothing but peaks illuminated by the sun against the terminator) spread in the newspapers as light signals from the “martians". In the light of those events Camille Flammarion entered the scene. He was a French astronomer working at Juvisy-sur Orge, an observatory installed with his own funds in a château which had been made available to him by its owner and was devoted to Mars observation. In it, Flammarion mounted his Bardou refractor telescope with a 24 cm aperture. He accepted the maritime interpretation of some features already observed on Mars and, for more, he was convinced that there was life there, which led him to identify vegetation on its surface and to publish, two years later, his book La planète Mars et ses conditions d’habitabilité, in which he asserted that the canals should be a construction of some sort of “human species” at a higher development stage than terrestrial humans, even though he could observe just a few of those depicted by Schiaparelli.
It has been asserted often that a main factor in the spreading of the idea of intelligent creatures living on Mars was the mistranslation of the Italian word canali as canals, which refers to artificial structures, instead of as channels, which refers to landforms. Nevertheless, it must be noted that there was already a strong inclination to believe in martian intelligent life, as the previous work of Flammarion exemplify. At the age of nineteen, he had published the book La Pluralité del mondes habités (1862), in which he tried to proof the existence of life in other worlds from the astronomical information available at that moment. The book was a best seller, preparing the public to think of Mars as the most likely and close example of inhabited planet apart from Earth. As another clue of the intensity of the “Martian life fever” trending, it is worth mentioning that Clara Goguet Guzman offered a prize in 1891 to the person able to implement a system to engage in communication with some higher intelligence from other celestial bodies.
On the other hand, as had been said already, Schiaparelli did not considered at first the possibility that their canali were the work of intelligent beings, and in their earlier articles the canals were always treated as natural features, so the inappropriate translation could have been an irrelevant detail. What probably did result transcendent was the graphic description of the canals, that was very favourable to the artificial interpretation.
Nevertheless, there were astronomers casting doubt on the existence of the canals, as was the case of Charles August Young (1834-1908) and, notably, Asaph Hall (1829-1907), who performed his observations from the US naval Observatory at Foggy Bottom, Washington, an unappropriated location due to the bad atmospheric conditions there, a circumstance which diminished the value of his assertions.

Figure 5. In 1890, after two oppositions using his new Repsold-Merz telescope, Schiaparelli described a whole network of canals as can be seen in this map. Note that the number of geminations increased, and the network extended over the entire northern hemisphere.

From the actual time and state of knowledge, maybe it is striking the timid response to Schiaparelli’s claims regarding the canals, but the observations were highly subjective at that moment, and much was unknown about the optical “interferences” that should be taken into account (physical, physiological etcetera). Telescopes used to be installed in the cities, and it was just starting to be considered the convenience of placing them on top of mounts from where the effects of the atmosphere are lesser. As for the colours described, the variations was wide depending on the optical behaviour of the different lenses and the personal sight of their respective users, being far more narrow in the case of observations performed with reflector telescopes, which are free of the chromatic aberration of the refractor ones. Therefore, there were no many objective criteria to assess the validity of a certain observation, being the prestige of the astronomer an important reference to assume or discard his results.
In any case, the number of those who saw the canals became overwhelming, and their descriptions of Mars surface became more and more distorted.

Mars Opositions of 1892-1894

William Henry Pickering (1858-1935), who observed Mars from the Harvard Observatory at Arequipa in 1892 with a refractor telescope 33 cm in aperture, used magnification factors at the eyepiece of 475 and even 1,140 for his observations, though it had been stablished that such a magnification was not adequate to see details. Even though, he described small lakes, snow fallings over some mountains, pointed out the possibility that the surface was partially covered by green vegetation and, of course, confirmed the existence of Schiaparelli’s canals. His own brother, Edward C. Pickering, who was the director of the Harvard College Observatory, disagreed with these “sensationalistic” results, which were published for the general enthusiasm in the New York Herald. Actually the rest of the observations by others astronomers during this opposition did not yield any remarkable outcome, maybe partially due to the fact that Mars was hardly observable from the northern hemisphere that time (while Arequipa is in the southern hemisphere, and the results of Pickering observations counted at first with a higher value).
Then Percival Lowell, the first son of a wealthy family from Boston, entered into the scenario. He had obtained a degree in mathematics at Harvard, and was an amateur astronomer looking for an occupation. After reading La Planete Mars by Flammarion, he was determined to devote his time to the telescopic observation of Mars before being contacted by Pickering, who was searching for funds to organise an observation campaign of the planet from Arizona during the opposition of 1894. Lowell provided the funds and, proving himself to be a kind of egocentric man, he imposed the name of Lowell Observatory on the facilities that were finally settled at Flagstaff, and assumed the absolute leadership of it ahead of Pickering.
He carried a 30 cm refractor telescope borrowed from Harvard, a brand new 46 cm refractor made by John Brashear, and a previous and deep seeded conviction that the main goal of the campaign should be the study of life on other worlds. From the very first moment Lowell considered the Schiaparelli’s canals a “self-evident” work of intelligent beings and, therefore, his subsequent observations seemed to be pointed to confirm the idea he had in mind, which led him to identify deserts, rivers, forests, oceans and so on, as well as to develop a whole theory to explain the existence of the canals and their evolution: they were engineering constructions to save the civilization in a desiccating planet by transporting water from the reservoirs in the polar caps to the rest of the populated areas.

Figure 6. Comparison between an actual map made from real images of Mars
(NASA-JPL) and those drawn respectively, from top to bottom, by Green and
Schiaparelli. Some real features can be recognised, and the higher fidelity in
Green’s one is appreciated.

These conclusions were reflected in the 1895 book Mars that gave place, together with a profusion of talks, conferences and articles, to a gigantic wave of public interest centred on the fantasies about Mars’ inhabitants. It is noteworthy that Lowell figured out his whole theory about the canals after just one month of observations from Flagstaff during this opposition, but it was enough to detonate the explosive spreading of the Mars tall tale among the astonished public. Meanwhile, in the academic sphere the controversy about the supposed martian environment and the existence of the canals themselves increased, and new clues of the incorrectness of Schiaparelli’s interpretations were cast on different aspects. William Wallace Campbell (1862–1938) performed spectroscopic measurements of Mars by means of the great telescope at Lick Observatory, to which he attached the convenient spectroscope. This observatory was built on top of Mount Hamilton, California, and counted with the largest refractor telescope in the world at the moment, a Clark 91 cm in aperture. With this powerful tool, Campbell stablished conclusively that there was no trace of water vapour in Mars’ atmosphere. Even Pickering had confirm from Flagstaff that the light from Mars was not polarized as should be expected of that reflected on the thought martian oceans, what supposed a setback for Schiaparelli’s maritime conception of the planet surface.
Edward Emerson Barnard, (1857–1923), also considered as a well-sighted astronomer, announced that in their observations from the Lick Observatory he couldn’t identify any of the canals, but rather a huge amount of tiny and indescribable details along the zones in which they were supposed to be. From then on, the mirage of the canals started to vanish within the scientific community under the flood of all kind of evidences that refuted their real existence. Many other astronomers invested time to verify it, observing invariably more and more confusing details instead of defined features, and concluding at last that they were most likely an artefact of the perception. Among then they could be mentioned Percy Braybrooke Molesworth (1867-1908) or, notably, Vincenzo Cerulli (1859-1927), who despite the fact that he had seen canals before, when using a Cooke refractor 39 cm in aperture, observed that the canal called Lethes disappeared in an intricate ensemble of patches.
The matter of the perception was started to be inquired as well, yielding interesting results. Edward W. Maunder (1851-1928), an astronomer working since 1873 at the Royal Observatory at Greenwich, had been observing Mars during the opposition in 1879, concluding that, though he could appreciate somehow something similar to Schiaparelli’s canals, they were at all a well-defined and sharp lines such as those drawn by him. Rather, he showed himself closer to the depiction by Nathaniel Green. Suspecting that some feature of the perception process could be playing a role, he designed an experiment together with J. E. Evans, Experiments as to the actuality of the canals of Mars, performed with children at the Royal Greenwich Hospital School. In it, the children were asked to observe a disk with figures composed of dots, which were drawn as lines when observed from a certain distance.
On the contrary, among the general public the idea of inhabited Mars kept on inflating thanks to the tenacity of Lowell who, on the other hand, began to lose credit as an astronomer. He claimed to have identify distinct points of reference in Venus, where nobody else had got such an achievement, and even dared to disregard the whole profession, within which he started to be considered as a notorious amateurish latecomer. The martian frenzy reached his peak in 1906, when Lowell published his book Mars and its canals, triggering the last and more intense wave of public interest on the martian fake.
The novel The war of the worlds (1898) by H. G. Wells, or the John Carter saga by Edgar Rice Burroughs started in 1912, illustrate how far-reaching the phenomenon was.
Apart from being a clear manifestation of the severe and well-known decoupling between science and society, the case of the Schiaparelli’s canals allows to set out the question about how a quite competent astronomer who was able to perform avant-garde studies that pushed the limits of knowledge in his field, could have embraced the crazy misinterpretation that his own observations gave rise to. At the end of his life, he admitted that his vision of the canals could have been a spurious consequence of the optics development at that moment that would be overcome along its further improvement. Yet, he never refused the existence of its canals as real martian features. Moreover, his speculations about the nature of them and the martian environment were sustained by him without paying attention to the increasing and solid evidences against them, in an attitude that doesn’t match anyway with what could be expected from a “scientific mind”. Maybe “the kind of mind” is precisely the aspect in which the essential matter lies. Let’s make some notes about the idea.
Science and technology are different subjects that act together in an intricate relationship, making almost impossible to distinguish one from another many times. In this same way, it could be said that there are scientists and technicians, put together in the professional group of “scientists”, but whose work is different as well. According to a conventional definition, science is the systematic process to build and organise knowledge in order to figure out testable explanations about nature, and technology is the collection of tools, services and techniques for the achievement of, in this case, scientific goals. In this sense, it can be pointed that was a prominent technician since he was extraordinarily skilled for the use of the telescope and the correspondent techniques, but he was not able to make science out of it, that is to say, he could not build nor organise knowledge to extract testable explanations from his observations. As an example of the opposite character, the scientist, it could be mentioned the figure of the famous naturalist Alfred Russel Wallace, who was somehow co-author of the evolution theory. He was concerned about the issue, though he was not directly involved in astronomy. Indeed, he never doubted that the Schiaparelli’s were real landforms, but he could see clearly and distinctly that everything else about Mars conception as a planet was a delirious nonsense. He devoted two books to the matter: Man’s place in the universe, published in 1904, in which he analysed the possibilities that other worlds could be inhabited from the knowledge gathered so far, and Is Mars habitable?, a demolishing response to Lowell’s Mars and its canals published in 1907. In it he stated that, due to the known conditions of temperature and atmospheric pressure, it was absurd to think that water, if present there, could be in the liquid state.
As for the canals, as was confirmed with the sending of the first probes to Mars already in the space era, they are not there, and they never were.
In summary, this is a brief story that illustrates how a scientific nonsense, under the confluence of certain circumstances, can swell out of control till, finally, pops without leaving any trace. It was born from a misinterpretation of a clever scientist, whose work was otherwise solvent and even brilliant, which corrupted a particular line of his work and gave place to a sort of exacerbated frenzy, fed with sensationalism. However, and despite its wide spread, it was in the end just an anecdotic event led by only two men who were followed by a little group of latecomers and astronomers not guided by a genuine scientific ambition. Behind that maelstrom, real scientists kept on working silently at their unhurried pace and, at last, their work was the one that allowed the astronomy to proceed along the right way.


[1]Areography was the word used to name the new discipline devoted to describe the topography of Mars (Ares), as an analogy to Geography for Earth.