Archaeology from Space How the Future Shapes Our Past

What is better than archaeology? How about space archaeology. More properly known as remote sensing by satellite, the use of satellite imagery has set the field or archaeology alight. And professor of anthropology Sarah Parcak is one of its most enthusiastic torch-bearers. In a book that overflows with wonder, honesty, and hope, she takes the reader on a grand tour of remote sensing, showing how it is transforming this discipline.

I first touched on this topic in my review of Tropical Forests in Prehistory, History, and Modernity, which mentioned the use of LiDAR to reveal the scope of jungle ruins. You will have been hard-pressed to miss these findings making news headlines. The rationale behind remote sensing is simple, says Parcak: Where do you begin? Given that, at the surface, many archaeological sites are covered under either sand, jungle, or modern infrastructure, how do you know what lurks beneath? And how do you even begin to decide where to dig? You would be surprised what you can see from the air.

Ever since we had cameras, hot air balloons, and the first aeroplanes, aerial photography became a thing. More concerted efforts came in the 1950s with the development of infrared technology and the spy satellite programmes of the Cold War, and in the ’60s with NASA launching satellites. But space archaeology had to wait until technological developments allowed for high-resolution images. That moment arrived in the 2000s and everything has gone a bit crazy since then.

The central part of Archaeology from Space is a mind-blowing tour of archaeological digs where remote sensing was involved. Parcak is an Egyptologist by training but has also worked on sites in Iceland, The Shetland Islands, Italy, and Newfoundland. And she provides an overview of some of the most spectacular finds others have made.

It is hard to overstate the significance of this technology. Take Tanis, a well-known site in Egypt. Where two centuries of work on the ground have focused on temples, tombs, and pyramids, Parcak inspected satellite images that revealed the whole city! Work on Easter Island, meanwhile, is overturning the long-held assumption that the Polynesians caused their own demise by cutting down their forests. Instead, introduced diseases by European explorers are to blame (see also The Statues that Walked). And the use of LiDAR in the Maya Biosphere Reserve in Central America has to date mapped more than 60,000 buildings (a finding Parcak calls insane). Particularly memorable is the story of archaeologist Arlen Chase, who found more ancient Maya sites in one night of feverishly inspecting satellite imagery than he had in 30 years working in the jungle. Probably the most important topic she tackles is wide-scale looting. In an era where online platforms such as eBay feed through to many potential buyers, there is scope for a massive black market. But here, too, satellite imagery has a role to play.

Despite the potential of this technology, Parcak is quick to recognise its limitations. Every potentially interesting site you identify needs to be ground-truthed with fieldwork. Even for a trained eye, it is easy to make mistakes, dismissing sites that are worthwhile or chasing phantoms that turn out to be false positives. With disarming honesty, Parcak tells of some of her biggest howlers. In the process, she reveals just what is involved in overseeing an excavation.

Midway the book she takes an unexpected step back from remote sensing. She combines the fictionalised life story of a woman in ancient Egypt with what we know about the transition of its Old Kingdom to its Middle Kingdom about 2200-2000 BC. This is Parcak’s home turf and her knowledgeable account is interesting, but I could not help but feel it broke the flow of the book a bit. Her next piece of fiction – picturing how an archaeologist in 2119 might go about things, complete with swarms of nano-drones and other futuristic archaeotech – is a relevant exercise in imagination, however.

See, archaeology now faces the same problem as e.g. genomics and astronomy that routinely reel in data by the tera- and petabytes: big data. It has never been easier to acquire more information than you could hope to process in several lifetimes. For the first time, we actually have tools to get to grips with the scale of what remains to be discovered. The estimated guesses Parcak gives are mind-boggling, but she revels in impossible odds. She is a dreamer, and I mean that in the best possible sense of the word. Technology is developing at a break-neck pace, allowing things we could not have imagined a few decades ago. Does anyone else remember that article where X-ray imaging was used to read charred papyrus sheets that were too fragile to unroll? Exactly. Suddenly her speculations on hyperspectral imaging and machine learning do not sound that implausible anymore.

And there is one other avenue Parcak has already bravely explored: crowdsourcing. She tells how, having won the million-dollar TED prize in 2016, she founded GlobalXplorer. This online, citizen-science platform allows anyone with an internet connection to help out locating sites of archaeological interest on satellite imagery. The response to the opening campaign was overwhelming and revealed many new and genuinely interesting sites. But Parcak dreams big. This is the woman who would have us map the entire world in the next ten years using this approach. What a hero.

One reviewer faulted the book for not talking enough about the technical details. Given that Parcak has authored the textbook Satellite Remote Sensing for Archaeology that gives you all the technical details you could want, this book is not the place for that. Even so, she explains why and how underground structures show up in satellite imagery (plant growth can be affected by what is buried underground, leading to visible crop marks), goes into some detail about hyperspectral imaging, and explains how seasonality and weather can influence your results.

It is true that Parcak sometimes goes off-script to talk about things close to her heart. Next to her chapter about historical Egypt, one chapter discusses the underrepresentation of women in archaeology. Seems like a very understandable and important diversion to me. I admit that I found some of her jokes borderline silly (they probably work wonderfully as one-liners in a presentation), but I had a lot of fun reading this book.

Archaeology from Space is a remarkably inspiring book, full of wonder and hope, buoyed by Parcak’s boundless enthusiasm and love for her profession. Harrison Ford might be too old to inspire a new generation of archaeologists as Indiana Jones, but he can safely pass his fedora on to Sarah Parcak.