Satellite archaeology uses changes in soil moisture to detect ruins

ScienceNews reports on a research team lead by Sarah Parcak of the University of Alabama, Birmingham that has used high-resolution satellite imagery covering all of Egypt to identify the potential sites of 17 lost pyramids, nearly 3000 ancient settlements, and 1000 tombs. They write:

Parcak began her study 11 years ago, searching for traces of ancient village walls buried under Egypt’s fields and desert sands. Obtaining images from both NASA and QuickBird satellites, she combined and analyzed data from the visible imagery as well as the infrared and thermal parts of the light spectrum. Through trial and error, she discovered that the most informative images were taken during the relatively wet weeks of late winter. During this period, buried mud-brick walls absorbed more moisture than usual, producing a subtle chemical signature in the overlying soil that showed up in high-resolution, infrared satellite images. These places became “our hot spots, the places that we could end up exploring on foot,” Parcak says.The team found 17 buried pyramid-shaped structures, including one at Saqqara, famed for its numerous pyramids. That sighting was confirmed by a team of Egyptian archaeologists who excavated part of what is now thought to be a late Middle Kingdom pyramid at the site. The other 16 structures look like pyramids from space but could be elite tombs, Parcak says. “Let’s be honest, we won’t know if those pyramids are pyramids until we excavate,” she says.

To further test some of the most recent satellite finds, Parcak enlisted the help of a French archaeological team already digging at a 3000-year-old site known as Tanis. The satellite data revealed a warren of mud-brick walls, mazelike streets, and large residences that may have housed the wealthy. So the French team chose a structure from the images and excavated there. Beneath about 30 centimeters of sediments, they discovered mud-brick walls. “They found an almost 100% correlation between what we see on the imagery and what we see on the ground,” Parcak says. “So this gives a significant amount of credence to what we see in the whole image.”

An article on BBC news about this work also features a video on their work, which is from a new BBC documentary.

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