Five myths about Mars

Earth's neighbor Mars is perhaps the most-studied planet beside our own in the solar system, with two robot rovers, Spiritand Opportunity, exploring the surface since 2004.

With Spirit no longer sending communications back to Earth but Opportunity still chugging along, NASA plans to land a third rover on the Martian surface; on Sunday, Aug. 5 at 10:30 p.m. PDT (1:30 a.m. EDT, 0530 GMT), Curiosity will carry 10 times the mass of scientific instruments as the earlier rovers to Mars, offering an opportunity to learn more than ever about the Red Planet.

Before Mars exploration began, though, limited information led to major misconceptions about the planet. Here are some of the myths that have persisted, and in some cases still persist, about Mars. [Full Mission Coverage of Mars Curiosity]

Myth #1: There's a face on Mars

In 1976, NASA's Viking 1 spacecraft snapped a photo of a Martian mesa that turned out rather eerie. Staring back from the surface of Mars was what appeared to be a human face.

Scientists shrugged the images of the "Face on Mars" off as a trick of light and shadow, but the public went mad. Conspiracy theorists figured the face was evidence of life on Mars. Supermarket tabloids loved it. It even showed up in a 1993 episode of television show "The X-Files" (episode: "Space").

In 1998, NASA's Mars Global Surveyor flew over the face and snapped the first sharp images of the landform since the Viking missions. This time, the mesa looked decidedly less human. The face got one more blow in 2001, when the same spacecraft snapped yet more photographs. In high resolution, the Face on Mars turns out to be an ordinary butte. [See Things on Mars: A History of Martian Illusions]

Myth #2: Martians built complex canals

Long before the Face on Mars mystified the public, planet-gazers were convinced that strange features dotted the surface of the Red Planet. In 1877, Italian astronomer Giovanni Schiaparelli observed what he called "canali," or canals, on the Martian surface. Could these features be evidence of irrigation and civilized life?

American businessman Percival Lowell certainly thought so. His drawings of the canals and his three books on the planet published between 1895 and 1908 spread the idea that intelligent life had built the canals in a desperate attempt to draw water from Mars' polar ice caps.

The first close-up pictures of Mars in 1965, taken by the spacecraft Mariner 4, put the canal theories to bed. It turns out no such features exist, and the canals are now known to be nothing but an optical illusion.

Myth #3: Mars has oceans

Less fanciful than the idea of canals on Mars, but still ultimately proven untrue, was the idea that Mars boasts oceans. In 1784, astronomer Sir William Herschel published a paper on his telescope observations of Mars. He got some things right, or at least close, including an axial tilt of 30 degrees (the actual number is 25.19).

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