A contrast-enhancing algorithm first applied to satellite imagery at NASA's Jet Propulsion Laboratory in Southern California is now widely used to study faded ancient images, NASA reported on Sept. 8, 2026. The method, decorrelation stretch, heightens contrasts in digital imagery so faint features become easier to see.

Around 2005, rock art enthusiast and medical imaging worker Jon Harman saw NASA Mars images made with and without the technique. He found a 1996 paper by JPL's Ronald Alley explaining how to do the algorithm, then built a plug-in called Dstretch for ImageJ, an open-source program developed by the National Institutes of Health. A test on an image from the Cave of San Borjitas in Baja California, Mexico, readily showed a yellow figure, NASA reported.

According to NASA, Harman, now retired in Pacifica, California, said he fulfills about 200 requests for Dstretch per year. He also created smartphone apps around 2010 that mimic decorrelation stretch; NASA said they have been downloaded thousands of times. The article says the tool has been used at sites in Norway, an Egyptian tomb and a Canadian park, and helped find buried remains of ancient Greek buildings and examine tattoos on mummified remains.