The Space Archaeologists

While still in graduate school, Parcak loaded an image of the Egyptian Nile River Delta taken by NASA’s Landsat Earth-observing satellite into a program called Erdas Imagine, a cross between Google Earth and Photoshop that geologists and climate scientists use to analyze satellite images. All natural features—trees, water, sand—reflect and absorb light differently, and the program can tease out any unique signature the researcher is looking for. Using data from known archaeological sites, Parcak had already figured out how to sort for the high organic matter and phosphorus content that marked Egyptian “tells,” or ancient house mounds. She processed the new images so that any tells would show up pink.

When she analyzed the images, her computer screen filled with pink splotches. “I thought, ‘Wait a minute, those can’t all be archaeological sites,’ ” Parcak recalls. But then she went into the field with a GPS receiver. At the pink points on the Landsat image, the delta’s flat green fields gave way to silty brown mounds: remnants of tells. Parcak has since used satellite data to uncover hundreds of sites in Egypt, none of them exposed to the naked eye.

NASA’s Archaeologists
Yet Parcak’s technique is not universally applicable; what works in the Egyptian delta won’t necessarily work in the Brazilian rainforest. Archaeologists have to tailor remote sensing to their sites. Satellite imagery is valuable for wet agricultural regions like the delta or heavily forested areas, while treeless plains or deserts call for radar.

In northern Angkor, which isn’t as heavily forested as Lingapura, Damian Evans uses synthetic aperture radar (SAR), a type of all-weather radar beamed from the belly of an aircraft that can gather far more information than ordinary radar alone. The time it takes for the radar waves to reach the ground and bounce back up to the aircraft records changes in elevation, and variations in soil humidity and other factors produce signals of differing “brightness,” thus allowing archaeologists to pick out ancient canals and man-made mounds.

The excitement around remote sensing means that archaeologists now work closely with NASA. Saturno and his partner at Marshall Space Flight Center, archaeologist Tom Sever, fly around the world to examine projects that might benefit from the space agency’s technology. In Pasadena, California, radar scientists at the Jet Propulsion Laboratory (JPL) are turning out increasingly sophisticated versions of SAR and working with archaeologists to apply them to their sites. And last year, NASA went official, creating a space-archaeology division under its Research Opportunities in Space and Earth Science program [see “The Past from 200 Miles Up,”]. The initial batch of grants allots $2 million to seven projects around the globe. Although that’s not a lot for the space agency, archaeologists, who are used to working with low budgets, consider it a vital infusion of resources and expertise. “This is just the beginning,” Sever says.

The Ground War
Archaeologists, like skilled workers in other professions, have not uniformly embraced the introduction of new technologies. The dynamic is in many ways embodied at Angkor. Once home to an illustrious civilization spanning 600 years and now containing the world’s largest temple, Angkor Wat (wat is the word for temple in Khmer), along with hundreds of subsidiary temples, the ancient city has long attracted aspiring Indiana Joneses. But in the past decade, those adventurers have had to bunk with unlikely company: indoor archaeologists more at home in a computer lab than a field camp.

Angkor’s early archaeologists were foot soldiers in a European battle to showcase colonial finds. At the turn of the 20th century, the British had fixed up India’s Taj Mahal, and the French, who controlled much of Southeast Asia, hurried to show off Angkor Wat. In 1907, the École Française d’Extrême-Orient (EFEO), a French research organization with 17 centers throughout Asia, opened an outpost in Siem Reap, near the temple, on the banks of an Angkorian canal.