Photograph by Louise Bray, BBC
With countless ancient cities and pyramids still buried below Egypt's endless sand, where do you point your shovel? Ask a satellite floating 400 miles overhead. Powerful space cameras and infrared imagery can now pinpoint and record structures less than two feet wide and completely invisible to the naked eye.
Sarah Parcak, an Egyptologist, is pioneering the young field of satellite archaeology, using futuristic tools to unlock secrets from the past and transform the way discoveries are made. "We're using satellites to help map and model cultural features that could never be seen on the ground because they're obscured by modernization, forests, or soil," she explains.
Parcak blends expertise with advanced computer programs, satellite imagery analysis, and old-fashioned digging to reveal thousands of new sites, including lost pyramids, temples, monasteries, tombs, homes, and even entire towns.
"The time and cost savings to the field of archaeology are enormous," Parcak reports. "Before doing fieldwork in Middle Egypt, I analyzed satellite imagery to determine exactly where I wanted to go. Within three weeks I found about 70 sites. If I had approached this as a traditional foot survey, it would have taken me three and a half years. Could I have covered an area as large? How would I have known where to look? Less than 1 percent of ancient Egypt has been discovered and excavated. With population pressures, urbanization, and modernization encroaching, we're in a race against time. Why not use the most advanced tools we have to map, quantify, and protect our past?"
The human eye can see only part of the light spectrum. With help from infrared satellite imagery, reflected light from different parts of the spectrum becomes visible. Ancient Egyptians typically built with mud bricks, which retain water and are denser than surrounding soil. Satellites detect those differences in density, and when viewed from hundreds of miles up, they can help archaeologists reveal outlines of buried settlements, temples, tombs, and roads.
"Imagery from space shows us very subtle changes at a pixel level," says Parcak. "We accentuate those differences on satellite maps by adding distinctly different colors to farmland, urban structures, archaeological sites, vegetation, and water. Then sophisticated computer algorithms tease out differences in a constant process of refinement. These extra eyes in the sky expose an entirely invisible world of lost cities."
One such city, Tanis, lies below Egypt's eastern delta. Almost none of the massive settlement has been excavated. Parcak used satellite imagery to collaborate with a French team working there.
"From space you can see the whole settlement's detailed network of streets and houses. Our map is incredibly clear; it literally looks like something you'd pull out to help you navigate a town you might visit today," she says. The team found an 80 percent correlation between the houses they unearthed and what the imagery showed. "It's not quite high resolution enough yet, but in the near future we'll see even more. For me the ‘aha' moment was realizing how accurate these maps can be. We've created a completely new plan of an ancient city no one has seen for 3,000 years."
Parcak stresses that these exciting moments happen only after plenty of painstaking preliminary research and analysis in the lab. "We don't just grab an image, flip it into the computer, and press a button. I've spent more than 10,000 hours of my life staring at satellite imagery to understand what I'm seeing."
In fact, she feels her most important contribution isn't discovering ancient sites, but writing the first methodology book on satellite archaeology, which will allow the next generation of students to learn and advance the new field. She points out that a big part of that methodology happens before ever viewing an image from space. "You need deep knowledge of historical events, the geology of how materials degrade over time, topography of landscapes, seasonal weather conditions, and the culture as a whole," she says.
Parcak looks forward to using data gleaned from the new technology to answer some of archaeology's biggest questions. For instance, why did Egypt's great pyramid age end? By revealing thousands of new sites, satellite maps show trends and population shifts scientists can relate to other important facts such as global climate events. Synthesizing the information leads Parcak to credit the sudden halt in pyramid construction to a well-documented global drought that forced migration to big cities where the Nile's flow still flourished.
"To me, these are the fascinating questions technology can help answer," she says. "I hope my work contributes to understanding long-term patterns of human behavior and how we survive, thrive, or fail during times of environmental, social, and economic crisis. How did we shape the landscape, and how did the landscape shape us?"
She stands amazed at the exponential rate technology is improving. "It's getting much better, much faster. High-resolution satellite images will soon portray objects less than one foot in size. There's even an aircraft sensor system that sends down hundreds of thousands of pulses of light measured at different return rates. It allows you to literally strip away vegetation and see entire cities beneath the rain forest canopy. This is the unbelievable future of archaeology."
As a child she remembers peering through a stereoscope, then state-of-the-art technology used by her grandfather, a renowned pioneer of aerial photography in forestry. That experience inspired her, on a whim, to enroll in a space archaeology course during her last university semester. "One course can change your life," she tells her own students today.
"This isn't just another ‘gee whiz' toy," she says. "It's a genuine scientific tool with proven, published results from Egypt to Syria to Italy to Easter Island. It has so much potential and possibility. It transforms every aspect about how we see and understand our past."
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