Meet the Martians
Johannes Kepler (1571-1630)
The telescope was invented during Kepler's life, but no one knows whether he ever saw Mars through one. In any case, he left no record if he did. Yet this astronomer still earns first place among Earth's Martians. Why? Because of what he did with observations of the Red Planet made by Tycho Brahe (1546-1601).
Brahe measured very accurately the position of Mars as it moved among the stars. These gave Kepler the data he needed to work out the planet's orbit around the Sun. Kepler was a follower of Nicolaus Copernicus, who argued that the Sun, not the Earth, was at the center of the solar system. Kepler thought the orbit of Mars would make a good proof of Copernicus' theory.
Unfortunately, he could not make Mars' motions fit into a circular orbit centered on the Sun, as Copernican theory required. Knowing that Tycho's observations were correct, Kepler worried over the problem for months.
Desperate to find an answer, Kepler took a bold step. He kept the Sun-centered part of Copernicus' theory but he threw out circular orbits. Mars, he said, follows an elliptical (oval) orbit, and so do all the other planets. This was a key discovery that helped create modern astronomy.
Christiaan Huygens (1629-1695)
Huygens was the first astronomer to see surface markings on Mars. Working with his brother Constantine and philosopher Benedict Spinoza, Huygens found new ways to grind lenses and make better telescopes. These led to several discoveries.
Today, Huygens is best known for discovering Saturn's ring. Earlier astronomers had poor-quality telescopes, and thus they could not see it correctly and did not understand what they saw. Huygens also discovered Titan, Saturn's largest moon.
Among Huygens' observations of Mars was a sketch he made on October 13, 1659. The sketch is crude but it shows a dark triangular feature that looks like Syrtis Major. Using this marking, Huygens found that Mars rotates about once every 24 hours and thus has a day slightly longer than Earth's.
Huygens was also interested in the possibility of extraterrestrial life, particularly on Mars. He speculated about what life would need to survive on a planet other than Earth.
Giovanni Domenico Cassini (1625-1712)
Cassini's Martian studies built on those of Huygens. In 1665 and 1666 Cassini determined the planet's rotation period to be 24 hours 40 minutes, which is within a minute of its correct figure. He was also the first to see the Martian polar caps, in 1666.
In this same period, Cassini (with another astronomer's help) determined the actual distance to Mars, and used this to measure the distance from Earth to the Sun. (His figure was about seven percent too small.)
It was a neat piece of work. Astronomers had determined accurately the relative distances from the Sun to each of the planets using their orbital periods. But the physical distance was unknown. So when Cassini measured Mars' distance from Earth, the rest of the values fell into place. Thus the actual size of the solar system became known for the first time.
Giovanni Schiaparelli (1835-1910)
The modern era for Mars begins with Giovanni Schiaparelli (SKYA-pa-rel-li). His observations were thorough and detailed, especially during the close approach of Mars to Earth in 1877. As a result they gave Martian studies a new importance among astronomers.
Schiaparelli observed Mars for years, spending long hours at the telescope eyepiece. He patiently waited for passing moments of extra-sharp visibility. In his observations he recorded many features new to astronomers and located them accurately on the Martian globe. His charts from the 1877 and 1879 observing seasons are landmarks in planetary mapping.
Among the features he plotted were what he called canali. These were straight, dark lines that had been glimpsed earlier by others. But Schiaparelli plotted many more canali than before. He even said that some of them seemed to become double between 1877 and 1879. Eventually, Schiaparelli mapped nearly 100 canali, although other experienced astronomers had difficulty seeing all of them.
Schiaparelli made another lasting contribution in the names he gave to Martian features. In large part, we still use them. Drawing from ancient Greek and Roman geography, Schiaparelli placed poetic names all across Mars — Memnonia, Aeolia, Hellas, Argyre, Tharsis, Ophir, even Utopia.
Percival Lowell (1855-1916)
Schiaparelli's canali were translated into English as "canals," and Mars studies have never been the same since. This is due mostly to one astronomer, Percival Lowell.
A rich Bostonian, Lowell became excited about Mars after reading reports of Schiaparelli's work, especially the canali. In 1894, Lowell built a large private observatory in Flagstaff, Arizona, to make observations of Mars.
Lowell drew nearly a thousand sketches of the Red Planet at the eyepiece of a 24-inch (61-cm) telescope. He also plotted more than 400 canals. Lowell was convinced the canals were made by intelligent beings, and he promoted this idea widely in books and public lectures in the early 20th century.
Lowell's Mars was inhabited by a dying civilization, held together by water-carrying canals. Because this idea appealed to many, it lasted in the public mind for decades. As a side effect, Lowell's fantasies gave planetary science — and Mars in particular — a bad reputation among scientists. For many years after Lowell, very few scientists bothered to study Mars.
Eugene Michael Antoniadi (1870-1944)
One of the few who did study Mars was Eugene Michael Antoniadi. Born in Greece, he worked in France and published in French. Starting in 1909 and continuing for about 25 years, Antoniadi observed Mars with an 81-cm (33-inch) telescope at the Meudon Observatory near Paris. He was a highly skilled observer and artist, making thousands of sketches and many beautiful (and accurate) maps.
On nights with the clearest seeing, Antoniadi found that smooth areas showed irregular markings. But these were difficult or impossible to capture with pencil and paper. (Photography was no help either because exposures lasted several seconds, blurring details.) Under excellent visibility, Antoniadi saw that canals broke up into chains of individual small spots.
In the end, Antoniadi became convinced that the "canals" weren't real. They were simply optical illusions caused by the human eye and brain straining to see details at the limit of visibility.
Carl Sagan (1934-1996)
Carl Sagan made contributions to planetary science in many areas, and was best known to the general public for his popular television series Cosmos, first broadcast in 1980.
Mars interested Sagan from the point of view of finding life outside of Earth. In 1965, NASA's Mariner 4 spacecraft (the first ever to photograph Mars close up) had shown a picture of a cold, dry, lifeless Mars. All the same, Sagan repeatedly urged NASA to sterilize future Mars probes because they might carry Earth microbes to Mars and harm any Martian life. In addition, he said, Earth bugs brought to Mars might confuse the results from biology experiments on spacecraft.
In many public talks and popular books, Sagan promoted the idea of life in the solar system and in the universe. In scientific papers and conferences, however, he took a more skeptical approach. Still, he said, it's worth looking because if we ever do find life outside of Earth, it would be a stupendous discovery.
Sagan played a direct role in Mars research mainly in connection with the twin Viking spacecraft. Launched in 1975, Viking was a highly ambitious project that sent two orbiters plus two non-roving landers. The goal for the landers was to search for life on the Martian surface. To do this, each carried a biology instrument package.
Launched separately, Viking 1 and 2 arrived at Mars in June (Viking 1) and August 1976 (Viking 2). Viking 1's lander set down in Chryse on July 20, 1976, while Viking 2's lander touched down in Utopia September 3, 1976.
Only one Viking biology experiment showed unusual activity that might have been due to life. Scientists have studied those results for more than 30 years. But most today are convinced that the activity came from a non-biological chemical reaction.
The failure of Viking to detect clear signs of life on Mars was a major blow for Sagan and for Mars scientists in general. It also put NASA's Mars plans on hold for many years. After Viking, NASA's next mission to Mars wasn't launched until 1992.
