A complex and colourful mural 45 metres wide and 4 metres high painted on canyon walls some 4,000 years ago, is being scanned with lasers to produce a high-resolution 3-D image, in efforts to gauge the mural's deterioration, detect images long ago weathered away, and protect it from the unintended consequences of a nearby reservoir.
     Panther Cave - so-named from the 4 metre long figure of a leaping red panther guarding its entrance - overlooks the Rio Grande about 80 kilometres west of Del Rio, and is among the best known of several hundred prehistoric pictograph sites that dot the steep, rugged canyons along the USA-Mexico border
     "They are ancient texts, not just drawing on walls," says Carolyn Boyd, head of the Shumla School, an archeological research centre working with state and federal agencies on the project.
     The two-week scanning process, extending into early June, will eventually give researchers a precise baseline to track what appears to be accelerated deterioration due to increased moisture from the Amistad Reservoir, and insects building nests or burrowing into the porous limestone walls.
     A camera about the size of a microwave oven passes over a 15 to 25 centimetre square on each scan, collecting images accurate to 1mm. Colour photographs are then overlaid on the images to give researchers a clear picture of how the site has changed over the centuries. Other images taken with colour-sensitive photo equipment reveal parts of the paintings no longer visible to the naked eye.

Edited from Associated Press, Beaumont Enterprise (29 May 2011)