The Universe in the Classroom

No. 25 - Fall 1993

© 1993, Astronomical Society of the Pacific, 390 Ashton Avenue, San Francisco, CA 94112.

The Face on Mars

The face on Mars
The "Face" on Mars (Courtesy NASA_

by Sally Stephens, Astronomical Society of the Pacific

The planet Mars has intrigued humans since we first began to study the sky. It is the only planet that looks red to the naked eye, which may explain why the ancient Greeks and Romans associated it with the bloody god of war. Spacecraft that visited Mars in the 1960s and 1970s found a freezing, arid, dead world. Nevertheless, the idea of life on Mars, and, in particular, intelligent life on Mars, fed by years of science fiction stories, persists in the public mind, despite the weight of scientific evidence against it.

This myth has surfaced again in the so-called "Face on Mars,'' a rock outcropping that looks like a human face when lit from the side. Astronomers see it as a mere optical illusion, proof of the power of human imagination. But a few, very vocal individuals see it as proof of an ancient Martian civilization. Some of them even go so far as to accuse NASA of deliberately destroying the billion-dollar Mars Observer spacecraft at the end of August to keep from having to admit that the Face is "real.'' Such extraordinary claims require extraordinary proof, which is sorely lacking in this case. But the Face on Mars is not the first time humans have been misled about evidence for life on our neighboring planet.

The Martian Canals
The Face on Mars
Is the Face Real?
Extraordinary Claims Require Extraordinary Proof
Activity #1 - Looking for patterns: The Man on the Moon
Activity #2 - Faces, Faces Everywhere
Bibliography: The Face on Mars
What Happened to Mars Observer
Viking's Search for Life

The Martian Canals

When early astronomers trained their crude telescopes on Mars, they could see few details of its surface beyond some dark patches and white polar caps. In some ways, the mysterious planet seemed tantalizingly like Earth. A Martian day is only 37 minutes longer than one on Earth. Mars' equator is tilted relative to the plane of its orbit around the Sun by almost the same amount as the Earth's, which gives Mars, like Earth, seasons. And the ice caps on its north and south poles wax and wane with the seasons. By the 1800s, Mars seemed enough like Earth that astronomers and science fiction writers began to dream of a Mars populated with intelligent, alien beings.

In 1877, Mars came within 56 million kilometers (35 million miles) of Earth, about as close as it ever gets (because its orbit is somewhat elongated, its distance at closest approach to Earth varies from year to year). Taking advantage of the close range, American astronomer Asaph Hall discovered two moons circling Mars. Other astronomers strained to learn as much as they could about the red planet. Using the 8-and-3/4-inch refracting telescope at the Brera Observatory in Milan, Italian astronomer Giovanni Schiaparelli reported seeing a network of very fine, regular lines crisscrossing the reddish deserts of Mars. He called them canali, which means "channels'' or "grooves,'' but the word was translated into English as "canals.'' Given the limited understanding of the Martian atmosphere and climate at the time, and the known similarities to Earth, many people jumped to the conclusion that Schiaparelli's canals had been constructed by intelligent beings.
Left: Drawing of Mars, done on October 11, 1916, showing "canals'' seen by an astronomer looking through a telescope. Right: Photograph of the Red Planet taken the next evening. (Courtesy Lowell Observatory)

Percival Lowell, a successful Boston businessman, was so captivated by this idea, that, in 1893, he built a major observatory in the clear skies of Flagstaff, Arizona to study the Martian canals (a great deal of other research has since been done at the Lowell Observatory, including the discovery of Pluto). Lowell was convinced that intelligent Martians had built a network of canals to pump water from the melting ice caps to dying cities in the desert.

Not all astronomers believed in the canals. In fact, many famous astronomers never saw them, including Asaph Hall. Those who did see canals rarely agreed on their locations and intensities; some said they were broad, diffuse stripes, while others maintained they had a thin, spider-web appearance. As time went on and more was learned about the red planet, astronomers realized that Mars was too cold and its atmosphere too thin for liquid water to exist on its surface. In 1971, the Mariner 9 spacecraft sent back to Earth the first really good, high-resolution maps of the planet. Absolutely no canals were seen, and the volcanoes, valleys and craters that were mapped didn't correspond to any feature seen by Lowell.

It turned out there never were any canals on Mars. When straining to look at things that are barely visible, the human eye tends to join faint but distinct markings together. That's what happened to the astronomers struggling to learn more about the surface of Mars. The Martian canals say more about human perception and imagination than anything else. As Carl Sagan said in Cosmos, "Lowell always said the regularity of the canals was an unmistakable sign that they were of intelligent origin. This is certainly true. The only unresolved question was which side of the telescope the intelligence was on."

The Face on Mars

A similar statement can be made about the Face on Mars. In 1976 two unmanned Viking spacecraft went into orbit around Mars. Each sent a lander down to the surface, while the orbiters radioed back over 60,000 photographs of the Martian surface. Not long after the orbiters began their mission, Viking scientists noticed a picture of a squarish, mile-long low hill or mesa in the Cydonia region of Mars that looked sort of like a face. They released the image to the press as a sort of joke, an example of our tendency to see apparently familiar shapes in complex landscapes. The researchers and the press recognized the Face as an unusual rock formation created by weathering. The dramatic low angle of late-afternoon lighting in the photo made the outcropping look like a face.

Three years later, two computer scientists with no particular expertise in Martian geology working for a contractor at NASA came across the image while going through the Viking photo archives. They experimented with some image-enhancement programs and concluded that the Face did not occur naturally. They also noticed several "pyramids'' near the Face, and published a book calling attention to the structures.

In the 1980s, Richard Hoagland, a science journalist, took up the cause of the Face on Mars in several books and numerous radio and TV appearances. In the scattered hills of Cydonia, Hoagland sees evidence of a ruined "city'' and "fort.'' He claims the city and the Face are aligned in a way that may have, in the manner of Stonehenge, pointed to the place where the sun rose on the Martian solstice half a million years ago (which Hoagland takes to be when the Face was made), although the orientation has no meaning today. Clearly, to Hoagland, this region of Mars is the result of a gigantic construction project by intelligent beings.

But who were they? And why does the Face look human? Hoagland has several theories. Perhaps evolution worked the same way on Mars as it did on Earth and so the Martians looked human. Or maybe a previously unknown, technologically advanced civilization from Earth's distant past traveled to Mars (or, alternatively, an advanced Martian civilization came to Earth long ago, and we look like them). Or perhaps the Face was built by some sophisticated extraterrestrials from beyond the solar system as a signal (or test) for us when we had reached a certain stage of technological evolution (rather like the black monolith in the movie 2001: A Space Odyssey).

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