New details obtained by Mars Express

Sep 22, 2006 09:40 GMT  ·  By

On 25 July 1976, NASA's Viking 1 orbiter took one of the most famous images from Mars: the so-called Face on Mars. The rocky formation resembling a human head is located in the Cydonia region in the Arabia Terra - a transition zone between the southern highlands and the northern plains of Mars (see the image of Mars below). This transition zone is characterized by wide, debris-filled valleys and isolated remnant mounds of various shapes and sizes.

Although NASA scientists had interpreted the "face" image as an optical illusion caused by the illumination angle of the Sun, the formation's surface morphology and the resulting shadows, the photo has triggered numerous speculations about its supposed artificial origin.

"The huge rock formation in the center, which resembles a human head, is formed by shadows giving the illusion of eyes, nose and mouth," said the original NASA press release. "The feature is 1.5 kilometers (one mile) across, with the sun angle at approximately 20 degrees. The speckled appearance of the image is due to bit errors, emphasized by enlargement of the photo. The picture was taken on July 25 from a range of 1873 kilometers (1162 miles)."

The popular speculations about the possible alien origin of the structure have been undermined in April 1998 when NASA's Mars Global Surveyor surveyed the region again. The much more detailed image showed that the structure's resemblance to a face is only remote. The satellite surveyed the region again in 2001 and further confirmed the same conclusion.

Now, the ESA's Mars Express has obtained even more detailed images of the Cydonia region. The High Resolution Stereo Camera (HRSC) photos include some of the most spectacular views of the Red Planet ever. The craft had tried to image the region from April 2004 to July 2006 but atmospheric dust and haze screened the rocky formations. But on 22 July, the atmospheric conditions finally allowed the craft to picture the "face" in unprecedented detail. The probe surveyed a wide area in Cydonia region at the best possible resolution and in 3D.

"These images of the Cydonia region on Mars are truly spectacular," said Dr Agustin Chicarro, ESA Mars Express Project Scientist. "They not only provide a completely fresh and detailed view of an area famous to fans of space myths worldwide, but also provide an impressive close-up over an area of great interest for planetary geologists, and show once more the high capability of the Mars Express camera."

Mars Express photographed the "face" structure from different directions. The views reveal an eroded structure probably covered by sand and displaying a massive western wall. Scientists think that this wall has formed via landslides, its entire mass moving downslope. The formation also has what geologists call "debris aprons", gently sloping areas surrounding hills or reliefs.

These debris aprons are frequently found in the Cydonia region at the foot of such remnant mounds but are often missing in smaller massifs. They probably consist of a mixture of rocky debris and ice and are the result of landslides. Sometimes the debris aprons have been covered by later lava flows.

Mars Express imaged many other structures in the region, including "pyramids" and a structure that looks, at least somewhat, like a skull. This naturally skull-shaped structure was never seen before.

The HRSC instrument and science team is led by Principal Investigator Prof. Dr Gerhard Neukum. The team consists of 45 co-investigators from 32 institutions and 10 nations.

Photo Credits: Original "Face on Mars": NASA/JPL. Mars Express photos: ESA/DLR/FU Berlin (G. Neukum), MOC (Malin Space Science Systems).

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