Early Observations of Mars
Much of what we know today about Mars would have never been possible if not for the work of early astronomers from the ancient civilizations of Babylonia, Egypt, and Greece, to the veritable contributions of Copernicus, Brahe, Kepler, and Lowell.
Babylonians
The Babylonians made careful astronomical observations and developed a sophisticated system of arithmetical computations for predicting astronomical phenomena such as eclipses. Their purposes were strictly calendrical and religious; however, they never attempted to explain the reasons for any of the movements they observed. Superstition was widespread, and many astronomical events were regarded as ominous---not just eclipses but even the risings of Venus were viewed as omens.
Eudoxus of Cnidus
Eudoxus of Cnidus was a brilliant mathematician that lived during the fourth century B.C. Eudoxus, who was a pupil at Plato's Academy, sought to reconcile Greek misconceptions concering planetary movement. The Ancient Greeks took for granted that the Earth was the center of the universe. They also assumed that the planets moved in a uniform circular motion. However, uniform motion around simple circles did not account for the complicated movements the Greeks actually observed; thus, they encountered the dilemma of showing how the observed movements could be reconciled with their principle of uniform circular motions. Eudoxus attacked this problem by developing an ingenious system of homocentric spheres, according to which the observed motion of a planet was produced by the independent motions of several internested spheres, each centered on the Earth. The significance of this system was that it was able to account for the retrogade movements; however, it did not explain if the spheres shared a common center and also why the planets varied in their brightness - in the case of Mars, some fiftyfold.
Aristarchus of Samos
Aristarchus of Samos, who is reknowned as the greatest of the ancient astronomers, had worked out a complete heliocentric system by 250 B.C., in which all the planets circled the Sun. Aristarchus received this inspiration of the heliocentric system by realizing that the most obvious explanation for the fluctuations in brightness was that the Earth was not the center of the all the motions. Aristarchus regarded the Earth as an ordinary planet: it rotated on its axis once every twenty-four hours, and it traveled in a circular path around the Sun with a period of one year. Thus, Aristarchus had solved the problem of the retrogade movements, which were now seen to be reflections of the Earth's orbital motion; they are displacements as the planets are viewed from different points as the Earth revolves around the Sun. The problem with Aristarchus's theory was that it assumed that the orbits of the planets were circular.
Cladius Ptolemy
Cladius Ptolemy, who lived in Alexandria during the second century A.D. continued upon the work that Aristarchus achieved and developed his infamous system of epicycles. The concept of epicycles, more commonly known as the Ptolemaic system, was detailed in his book The Almagest. According to the theory, each planet was taken to move around a small circle known as an epicycle, which in turn moved around a large circle centered on the earth. The combined motion of its epicycle and deferent caused each planet to swing in near the Earth at times; therefore, producing the retrogade movements. Ptolemy then made the large circles slightly eccentric to the earth; however, this did not account for the planets' movements. Thus, Ptolemy found a point from which the planet's motion around the large cirlce would appear uniform; it was located a short distance from the center in the opposite direction from the Earth. The significance of Ptolemy's contribution was that it abandoned the principle of circular motions completely.
Nicolaus Copernicus
Nicolaus Copernicus was a Polish canon at the Cathedral of Frauenberg who was able to correct both Aristarchus's and Ptolemy's theories by bringing back the heliocentric system and refining it. The Sun rather than the Earth was the center of the system, and the retrogade movements, especially in the case of Mars, were mere reflections of the Earth's own motion in its orbit. According to Copernicus, this occurred because of the earth changing its position in its large circle. However, Copernicus soon discovered through his observations that his hypothesis of circular orbits around the Sun did not agree with the observed movements of the planets; thus, he responded by by bringing up eccentric cycles and epicycles; however, he did reduce the number as compared to Ptolemy. Despite these inconsistencies, Copernicus, more importantly, was able to grasp the essential point.
Tycho Brahe
Tycho Brahe, who was born in 1546, three years after Copernicus's death, was a fervent scientist who worked at compiling a star catalog and an extensive archive of intricate observations of the planets for the better part of his life. In 1583, Brahe observed that Mars moved retrograde at a rate of nearly half a degree a day; thus, this proved that Mars could approach much closer to the earth than the Sun, which was true in the Copernican system but not the Ptolemaic. Brahe responded by developing a system in which the Earth remaind at the center, while the planets went around the Sun, and the Sun circled the Earth. This system was known as the Tychonic system.
Johannes Kepler
Johannes Kepler, a contemporary of Tycho Brahe, believed the Coperican system had some truth in it; thus; he began his quest in correcting it. Kepler at once corrected it by making the plane of Earth's orbit pass through the true Sun, as opposed to Copernicus's theory of the Earth revolving around the mean Sun. Kepler further succeeded with his consistency by discovering that the orbit of Mars was inclined to the Earth's by a constant angle of I' 50". Kepler's next task was trying to trace the shape of the planets' orbit without any preconception as to what it might be. To accomplish this, Kepler first set out by examining the Earth's motion around the Sun. By considering two of Brahe's observations of Mars in which the planet had been at the same place, but regarding them from the perspective of an observer on Mars as opposed to Earth, Kepler was able to show that Earth's orbit was as eccentric as those of the other planets. With this information at his hand, Kepler was able to calculate the distance from Mars to the Sun. Since Kepler calculated the angle that Mars makes relative to the Sun at two points, he could define the Sun-Mars distance in terms of the Sun-Earth distance. After struggling to determine that the Earth's orbit was an oval of some kind, Kepler went back to his Mar's "problem". In 1604, Kepler realized that the orbit of Mars was an elliptical path; however, what he also realized was that each planet follows this same elliptical path.
Christiaan Huygens
A great Dutch astronomer, Christiaan Huygens was the leading astronomer of his time in discovering patches on Mars. Beginning in 1655, at the age of twenty-six, Huygens began experimenting with new ways of figuring lenses for telescopes. During these experiments, he devised the first compound eyepiece, known as the Huygenian. By March of 1655, Huygenian has created a fully functional telescope that was able to detect Saturn's largest moon, Titan. In addition, he was able to solve the enigma introduced by Galileo by showing that Saturn was surrounded by a ring. Huygens also observed Mars. On November 28, 1659, Huygen found a V-shaped marking, which was the Syrtis Major; the most conspicuous of all the dark areas on Mars.
Giovanni Domenico Cassini
Born in 1625 at Perinaldo, France, Cassini was bound for telescopic glory. In 1664, Cassini made out dark blots and various temporary spots on Jupiter. In 1666, he recorded spots on Venus and began his work on Mars. He detected several patches on the Red Planet; however, his observations were hampered by the difficult atmospheric conditions and the quality of the telescopes at the time. In 1671, with a seventeen foot telescope, Cassini discovered a satellite of Saturn, Iapetus. A year later, with a thirty four foot telescope he found another, Rhea. In 1684, with a the aid of a one-hundred and thirty six foot telescope, he discovered two more satellites of Saturn, Dione and Tethys. Cassini's emphasis was never fully at Mars at all; however, he was key in working out the distance to Mars and, more importantly, he is noted as a pioneer of Mars exploration with modern day equipment.
Percival Lowell
American
astronomer, who made significant observations of the planets. He is best known for
his belief that there are canals on the surface of Mars and that these canals provide
evidence for the existence of intelligent life there. Born in Boston, Massachusetts,
and educated at Harvard University, Lowell traveled in Japan and Korea from 1877 until
1893 and later wrote books about East Asia. In 1894 he founded and became director
of the Lowell Observatory at Flagstaff, Arizona. From 1902 until his death, he was
nonresident professor of astronomy at the Massachusetts Institute of Technology. He
predicted the discovery of Pluto, which astronomers first observed in 1930 at the Lowell
Observatory. Lowell's writings include Mars and Its Canals, and Memoir on
a Trans-Nept.Planet (1915),
and The Genesis of the Planets (1916).