Unmasking the Face on Mars

A 1976 Viking 1 photograph of the Face on Mars. Click here for a 2001 photo from Mars Global Surveyor that reveals the true appearance of the Face.

And so on April 5, 1998, when Mars Global Surveyor flew over Cydonia for the first time, Michael Malin and his Mars Orbiter Camera (MOC) team snapped a picture ten times sharper than the original Viking photos. Thousands of anxious web surfers were waiting when the image first appeared on a JPL web site, revealing ... a natural landform. There was no alien monument after all.

But not everyone was satisfied. The Face on Mars is located at 41 degrees north martian latitude where it was winter in April '98 - a cloudy time of year on the Red Planet. The camera on board MGS had to peer through wispy clouds to see the Face. Perhaps, said sceptics, alien markings were hidden by haze.

Mission controllers prepared to look again. "It's not easy to target Cydonia," says Garvin. "In fact, it's hard work." Mars Global Surveyor is a mapping spacecraft that normally looks straight down and scans the planet like a fax machine in narrow 2.5 km-wide strips. "We just don't pass over the Face very often," he noted.

Nevertheless, on April 8, 2001 - a cloudless summer day in Cydonia - Mars Global Surveyor drew close enough for a second look. "We had to roll the spacecraft 25 degrees to centre the Face in the field of view," said Garvin. "Malin's team captured an extraordinary photo using the camera's absolute maximum resolution." Each pixel in the 2001 image spans 1.56 meters, compared to 43 meters per pixel in the best 1976 Viking photo.

Side by side: a Viking 1 photo from 1976, a Mars Global Surveyor (MGS) image from 1998, and the latest MGS image from 2001.

"As a rule of thumb, you can discern things in a digital image 3 times bigger than the pixel size," he added. "So, if there were objects in this picture like airplanes on the ground or Egyptian-style pyramids or even small shacks, you could see what they were!"