Space Archaeology - exploring ancient history from space

This false color space radar image shows the area surrounding the ancient city of Ubar on the Arabian peninsula. The red streaks are tracks leading to the site created by the city’s inhabitants thousands of years ago. Credit: Nasa/JPL-Caltech

This false color space radar image shows the area surrounding the ancient city of Ubar on the Arabian peninsula. The red streaks are tracks leading to the site created by the city’s inhabitants thousands of years ago. Credit: Nasa/JPL-Caltech

Space isn’t just about the future. Archaeologists - professional and amateur - are using satellite images to uncover evidence of human history. Searching for sites of ancient civilizations is the most expensive and time-consuming part of archaeologists’ job. The cost of flying aircraft over terrain and travelling to potential sites, combined with the time evaluating sites that turn up empty, comes at the expense of the real field work. As early as the 1960s archaeologists speculated that observations from space could make their jobs much easier, but technical limitations and Cold War security concerns kept archaeologists from using satellite data as a standard tool.

This space radar image of Cambodia's temples in Angkor helped uncover ancient canals and previously unknown structures hidden beneath the forest canopy. Credit: Nasa/JPL-Caltech

This space radar image of Cambodia's temples in Angkor helped uncover ancient canals and previously unknown structures hidden beneath the forest canopy. Credit: Nasa/JPL-Caltech

Things began to change as the 20th Century came to a close. Throughout the 1980s and 1990s, Nasa sent synthetic aperture radar experiments into orbit on the Space Shuttle. Images from these missions let scientists discover ancient riverbeds and roads beneath the sands of the Sahara and jungles of Cambodia. At the same time the internet and digital technologies made images from the USGS Landsat system more accessible. 

Then, after the fall of the Berlin Wall, the US government declassified high resolution images from the Corona spy satellite program. Even though the images were 20-30 years old, they were much higher resolution than anything the public had seen before.

Egyptology from Space

Among those taking advantage of the new data was University of Alabama egyptologist Sarah Parcak. (Her website autoplays ancient-egypty music, so mute your speakers if you're at work) Parcak used Corona and Landsat images in the Armana Project to search for evidence of Late Roman civilization along the Nile River. The last detailed archaeological survey of the area was conducted over 200 years ago. At 450 square kilometers, the area was much too large for conventional ground or aerial surveys - but not for satellites in space. 98% of the sites Parcak’s team identified held the remains of ancient Egyptian civilizations. 

Parcak has done much to establish satellite remote sensing as a standard part of the archaeological toolbox. She even wrote the book on space archaeology: Satellite Remote Sensing for Archaeology (affiliate link) was the first undergraduate-level introduction to the history and techniques of space archaeology. Parcak also popularizes space archaeology through TED Talks and documentaries with the BBC and the Discovery Channel. (sorry about all the autoplays)

Surfing for Ancient Rome

You don’t need to be a professional archaeologist to find ancient ruins in satellite imagery. Luca Mori decided to kill some time in 2005 by exploring the area around his hometown of Sorbolo in northern Italy. Rather than hike around, Mori did what any good programmer would do: he used Google Earth. At one point he saw the large, regular shape of something buried under a nearby field.“"At first I thought it was a stain on the photograph," he later explained to the BBC. "But when I zoomed in, I saw that there was something under the earth." A phone call to a local university brought in a team of  archaeologists who determined that the site had been a Roman villa built more than 2000 years ago.

The brighter area in this field was once the channel of a nearby river. Mori found the Roman villa after processing the image.

Amateurs like Mori don’t have the expertise to use the full range of space data the professionals have at their disposal. But they do have one advantage over the pros: time.

Thousands Search for Genghis Khan

Crowdsourcing combines the strengths of professionals and amateurs. The pros use their skills and experience to set priorities and develop easy-to-use interfaces. The amateurs donate their free time, ability to recognize patterns, and numbers. Together, they achieve results the professionals could never get on their own.

University of California San Diego scientist Albert Yu-Min Lin decided to combine satellite images, crowdsourcing, and archaeology when he created the Valley of the Khans Project. The challenge his team faced was finding a way to search for archaeological sites in Mongolia without disturbing the sites or revealing their locations. Ultimately, Lin and his team hoped to find the long-lost tomb of Genghis Khan. 

Lin created Field Expedition: Mongolia, a National Geographic Society site that let amateurs from around the world explore satellite images of the Mongolian steppe for ancient structures and buried roads. By the project’s end they classified over 2,300,000 features, contributing the equivalent of 18 years of effort.  

During field expeditions to Mongolia, Lin and his fellow archaeologists visited the 55 sites found by these amateur explorers. Combining satellite data and the crowdsourced map with on-site aerial images and ground-penetrating radar, the scientists mapped the ancient sites without disturbing them. None were Genghis Kahn’s tomb, but the discoveries couldn’t have been made as quickly and on such a large scale without widespread public participation.

The Golden Age of Space Archaeology

Lin went on to co-found Tomnod, a company that creates satellite-based crowdsourcing projects with a social purpose, using the technology created for the Valley of the Khans project. Tomnod. Projects have enlisted the public to map damage from natural disasters, the spread of invasive species, and even helped search for the missing Malaysian Airlines Flight 370. DigitalGlobe, the company whose satellites provide the high-resolution images we see in Google Maps, bought Tomnod in 2013 to expand its own socially-driven space program. 

We are only in the early days of space archaeology’s Golden Age. As new commercial satellites like DigitalGlobe’s WorldView-3 provide higher resolution images across more of the electromagnetic spectrum, professional archaeologists like Sarah Parcak will have even more data at their fingertips. “We found what we think are 3,000 previously unknown sites… I think I’ve only found a fraction of the sites that are there,” Parcak told DigitalGlobe in this video promoting its next-generation satellite.

The data tsunami that swept professional astronomy over the past 3 decades is about to sweep professional archaeology as companies like DigitalGlobe, Planet Labs, and UrtheCast deploy hundreds of cameras in orbit. Combined with the power of crowdsourcing, that means more opportunities for amateurs to help pros use space to uncover our ancient origins.