Archaeology from Space Page 7

  These larger buildings are a bit easier to see archaeologically, while smaller outbuildings can be more ambiguous. Doug and his team had developed intensive survey techniques to map larger farmsteads, for example, by following ancient trash deposits or middens23 close to more noticeable central farm buildings, but they had trouble locating the smaller buildings. It was not economically feasible for them to dig test pits every 5 meters, and the chances of missing the outbuildings would still be high.

  Putting the Imagery to the Test

  My team and I had already searched Iceland using Google Earth, attempting to get a sense of what Icelandic structures looked like from space—we needed to see the full Viking-to-modern range of farm and building types. Ancient field boundaries still in use today are easy to spot, though most of what’s visible on the surface is not Viking, but post-Norwegian rule (1262–1380 AD). Many of the sites we “discovered” were already known,24 but at least we got a good sense of the types of features to look for, their sizes, and their possible spatial relationships to the main farmsteads.

  But here’s the big problem: typically, in the United Kingdom, you find a ditch buried in a field, or, in Egypt, a stone tomb in the desert. Material X is very different from soil/sand/vegetation Y, and enough of the building material has degraded on the surface to be detectable from space using parts of the light spectrum we cannot see. It is invisible, or barely visible, on the ground. But here in Iceland, my team and I needed to find the foundations of small, degraded ancient turf structures, hidden in massive turf fields. That’s a needle in a haystack made of needles.

  The BBC thought it would be fun to go needle hunting during a live recording. After we analyzed the satellite imagery, several intriguing spots appeared in the Skagafjörður survey area. Doug selected some of them to search for using a simple auger—a small, handheld drill about two inches across. He explained that it was a million-to-one chance of hitting Viking archaeology with the core.

  He and his team had the coordinates of the structure we had seen from space, and they did their best to flag its location by measuring out from the field edges. Satellite imagery can be off by a few meters, which is not a big deal when you have other nearby structures to calibrate distance, but these walls measured less than 1 meter across. Even a small error would mean that we would miss them entirely.

  We approached one of Doug’s flagged areas. He asked me to stamp down on the core and give it a twist, so I did. It was like my first time on a pogo stick. I got rejected live on camera by the hard ground, which did wonders for my confidence and earned numerous snickers from the team.

  “Once more! With feeling,” Doug said. Somehow I got the thing in the ground and then twisted. We went down about 20 centimeters.

  Doug pulled it up, flipped it open, and cut the turf tube in half. He had a huge smile on his face.

  “Do you have any idea what you are looking at?”

  “It’d be strange if I did,” I replied. He pointed out cool grayish-white lines crisscrossing the turf and explained that each one represented a volcanic eruption.25 Iceland’s volcanoes are consistently lively. Datable by corroboration with ice-core and tree-ring dating, eruptions occurred before, during, and after the main period of Viking occupation, so Icelandic archaeologists can use their evidence in the soil to estimate the date of occupation layers. Doug then pointed to the bottom part of the core.

  “What you have here is a piece from a turf wall! Probably medieval.”

  Talk about reassured. We then dug a quick test trench to expose part of the wall.

  While I was disappointed to learn the wall was not Viking, Doug and his team assured me that it was a big step for them. Still, I had hoped it would be easier to spot potential Norse remains, versus medieval, from the satellite imagery. Not helping were all the modern people living on top of ancient Viking farms. Things would obviously be much harder than I had anticipated.

  Meanwhile, Back at the Dig House

  That night after dinner—though “night” in Iceland during August is a relative term—we gathered in the dig house. Red-and-white survey poles leaned against the walls, surrounded by muddy shoes and coats. It wasn’t Egypt, but I felt at home. Doug was hunched over his computer with a team member looking at 3-D reconstructions of the day’s excavation work created from aerial photos.26

  After geeking out at beautiful photographs of excavated burials, I joined Doug’s motley crew at a long table, where everyone was at work processing the data they had collected that day. I started reexamining the satellite imagery of the area and noticed the strange image angle—it looked as if a giant had twisted a massive checkerboard.

  It made no sense at first. But now, having visited the landscape, I saw how the foot of the mountain sloped gently down to the water. This can cause distortion on satellite imagery. If you didn’t know you were looking at it, that would be easy to miss.27

  Armed with new, on-the-ground knowledge—landscape, vegetation type, and what buried turf actually looked like underfoot—I began to reprocess the satellite data and adapt the processing techniques. The time crept on, but my internal clock barely registered a second. The sand in the hourglass just floated.

  As curious shapes started to emerge, I asked the Viking specialists what they thought. Getting instantaneous feedback and encouragement from the experts of a site as I processed the data must have been the most satisfying scientific evening of my career.

  Eventually, I had about a half dozen features—walls maybe?—that the team agreed would be well worth exploring. I left at about 2:30 a.m., walking on the thin air of the early morning up the hill to my tiny hotel room. I took a final look at the gray-brown mountains exploding out of the ground, and the absolute stillness froze me in place. It was a land purpose-built for legends, and it seemed appropriate to thank Odin and Freya for their blessings.

  Several of those buried features did indeed end up dating to the Viking period.

  Finding outbuildings may not seem like much, nor do they make headlines, but they set archaeologists’ minds alight. Tiny details matter to us. Outbuildings, collectively, tell us how the larger structures and farms could function. When a central farmhouse has associated buildings like a dairy for storing milk and a smithy for smelting iron tools, chances are good the farm was doing well. A lack of outbuildings adds other details to the bigger picture, and suggests the farmers were poor, perhaps struggling. And if the larger farms had shrunk over time, that shrinkage might be connected to declining resources caused by war, famine, or climate change. Now we don’t just have a small building. We have a story.

  Map showing location of Papa Stour [MAP COURTESY CHASE CHILDS]

  Small walls represent a tiny piece of what satellite imagery can discover. Sometimes an accidental find or something you dismiss as modern can turn out to be so much more.

  From Iceland to Scotland

  On the northwestern tip of the United Kingdom, the Shetland Isles are a craggy mass of hills, sheep, and fields. Some 1,300 years ago, the Vikings made their way 300 kilometers west from Norway and conquered the area.28 By the ninth century AD, they had established a stone-built stronghold at Jarlshof, the largest visible Viking site in the United Kingdom, which was occupied for nearly 500 years.29

  Here, in Scotland, again, my team and I were tasked with locating probable Norse sites. In each case, we’d study the region, poring over excavation and survey reports for what we might discover. Once we determined that a site had potential, we examined satellite databases for local imagery. No imagery, no go.

  And it had to be the right imagery. We needed data from the summer or early fall for maximum differences in vegetation health.30 We chose eight sites for ground investigation. On some, we could see Viking construction clearly. A longhouse is a longhouse is a longhouse.

  Except when it isn’t. At one promising site in Scotland, we saw a clear curving wall in turf and got excited. When a team went out to examine the location, they found the farmers had cut a longho
use-shaped building out of the modern turf, just to trick us.

  A Rune with a View

  And then there was the case of North House in Papa Stour. About 50 years ago, Andy Holt and Sabina Holt-Brook moved to a tiny island on the western side of the Shetlands to raise their family. A visionary young couple, they wanted to create a sustainable, organic farm, 40 years before such homesteads came into vogue. Naturally, when people dig their garden, they remove old bricks and debris. At North House, the couple kept finding odd carved stones, which they kept in a basket by the door. One day they discovered a larger angled disk with etched markings.

  When they showed the find to local experts, they were excited to learn they had a loom stone, used by Vikings in weaving wool.31 This one was special: it was marked with runes, Norse writing, showing that whoever had used it was literate. Literacy was rare and elite. Somewhere on their property was a rich Viking settlement or structure.

  When our team processed satellite data from Papa Stour, a series of clear straight lines appeared next to North House. My recommendation was to dismiss the site. It seemed suspiciously modern. Given the way we had processed the data, the feature showed up as a lurid pink stripe. It was probably a gas or water line.

  We sent all the processed data to various experts for assessment. When I learned the BBC had chosen Papa Stour as their site to film, I was shocked. I emailed them.

  On-the-ground photo of the excavated wall near North House [PHOTO BY THE AUTHOR]

  “Hey, that place ranked last for us, eighth out of the eight sites for which we had data. Do you want to film digging up a 19th-century water line?”

  I was told the decision was out of my hands and to get ready to fly to Scotland.

  Once again an Egyptologist in a strange land, I met the BBC producer in one of the tiniest airports ever. My son’s Playmobil airport serves more people. From there, we drove quickly to make the ferry. Beyond the stinging spray of the water, an otherworldly landscape rolled by. Sheep dotted the rugged green outcrops around us, moving like mist-shrouded cotton balls.

  “So, have you found anything interesting yet?” I asked the director, Nathan. He gave me a cryptic smile.

  “You’ll see.”

  Something I do not understand about the television world is their yen for a big reveal with the presenter, to catch the “Oh my God!” moment of discovery. It frustrated the crap out of me. The team from the local archaeology unit had worked at Papa Stour for two days, but I was in the dark.

  We arrived at North House, now a beautiful bed-and-breakfast after its earlier life as a commune in the 1970s, overlooking the gray-blue Norwegian Sea. Normally, B&Bs do not have bowls of Norse artifacts that greet you as you walk inside. The production team kept me away from the excavations in the back garden until I was miked up. By then, the director had a wicked glint in his eye.

  The Anomalous Anomaly

  Given the mood and joking atmosphere, I anticipated good news, but nothing prepared me for when I walked through the gate and saw the exposed “anomaly” in a 20-by-10-meter garden, with the sea cliffs to the left and the fairy-tale house on the right.

  It was a stone structure, some 15 meters long, as if a slate garden wall had sunk a meter into the ground, with additional stone offshoots. I realized, in that moment, that my caution had nearly cost us the chance to see something ancient. The “whoa” from me captured on camera is genuine.

  The Regional Archaeologist for Shetland, Val Turner, met me for a tour. Prior to excavating, the team used a simple probe, proving low tech can work just as well as high tech, and had started to dig in two trenches: one near the central part of the wall, and another to the south, where it seemed to disappear. The wall was strongly built, with well-laid slate flooring, while the southern trench had something even more exciting: fragments of soapstone vessels that hinted at the site’s Viking date.32

  Over the next two days, I got to play in the 1,200-year-old sandbox. Digging deeper in the northern trench, we found layers of floor after floor, suggesting that there had been at least 400 years of occupation at the site. During a tea break at the North House kitchen table, Tom Horne, an archaeologist and friend with boundless energy, came bouncing up to me with an impish grin. He whispered to the director, who said, “Outside, now!”

  When archaeologists uncover an extraordinary object, the energy of a site changes. Everyone looks like children on Christmas who have gotten exactly what they want. There was an electricity in the garden.

  Carnelian jewel excavated at the dig site near North House [PHOTO BY THE AUTHOR]

  “Hold out your hand,” said Tom and placed a lustrous orange-brown gemstone into my palm.

  “What!” I exclaimed. “How did you see this?”

  “I have magic eyes. Just like your satellites.”

  I held the dime-sized stone between my thumb and forefinger. Faceted and polished, it would not have been out of place in any modern ring. At first it looked like amber, but holding it up to the light, I saw a fiery orange glow.

  Carnelian! Even better. It reminded me of my archaeological home some 2,500 miles away, where the ancient Egyptians loved carnelian for their jewelry.33 For the Vikings, carnelian was an elite item, only found on sites like Birka, in Sweden, a major trading center.34 It likely was mined somewhere in the region of the Black Sea. Whoever owned that piece, whether set into a brooch or a ring, had been a very important person.

  Putting the evidence together, we recognized that we had a potential Norse stronghold on our hands.

  In a document written in 1299, a corruption case was brought against a local ruler, Lord Thorvald Thoresson,35 who had been accused of embezzling rent collections. He wanted to show his innocence, so he invited witnesses to testify. One of these witness meetings may have happened in the living room of the future ruler of Norway, Duke Haakon, somewhere on Papa Stour. Prior to our work there, archaeologists had pinpointed the duke’s farm as the Biggings, an excavated 12th- and 13th-century AD structure.36

  But this new Viking structure, located in a strategic position next to a beach, could actually represent his home. After a few days’ excavation, we had barely scraped the surface, literally, and had already uncovered numerous rooms. Walking on the beach below, I could see obvious stone walls exposed along the cliff edge, showing that the site was once far bigger. Sadly, I had to leave, and the excavation was backfilled to protect it. More discoveries await us there in future.

  Amped for Amphitheaters

  I admit when I am wrong, and now that I am the mother of a very loud and opinionated five-year-old, I am reminded often when I am. The Papa Stour case kept me on my toes and has since made me question all my ambiguous results.

  However, the most embarrassing moment of my career took place six years earlier, when I was expecting that five-year-old. On a previous BBC program, I had the chance to collaborate with a team in Italy that turned my own perception of new technologies, both space and ground based, on its head.

  Flying into Rome’s Fiumicino airport, you can look down and see a strange hexagon amid the urbanized landscape and fields.

  Just a stone’s throw from the runway lies one of Italy’s most fascinating archaeological sites, Portus, where some of mapping’s hottest technological developments are being applied. Portus was Rome’s great trading center about 1,900 years ago. Located along the Mediterranean coastline in antiquity, it was founded under Emperor Claudius in 42 AD and expanded by Emperor Trajan during his reign between 98 and 117 AD, serving as a key redistribution center connected to the major port of Ostia nearby.37 Today, the ancient coastline is 4 kilometers inland, as silt deposited over time by the River Tiber has gradually filled in the large, protected harbor.38

  The ancient site had a great deal in common with an Amazon warehouse of today. Goods flowed into Portus from across the Roman Empire, from Egyptian wines to Arabian perfumes. Sailing into the harbor, ships were guided by a lighthouse designed after the famous lighthouse of Alexandria. The vessels then e
ased into the hexagonal basin to dock at warehouses and off-load. Boat repair sheds also dotted the basin, one-stop shopping for captains and warehouse managers. Goods were loaded onto smaller boats, which sailed northeast toward Rome along the Tiber. Because of its bustling shipping business, Portus was a thriving community, with housing, warehouses, roads, a cemetery, and a marble quarry.39 And probably a dozen brothels, speaking of delivery.

  Map showing location of Portus [MAP COURTESY CHASE CHILDS]

  There is a rich history of archaeological exploration at Portus. Today, Simon Keay, an affable professor based at the University of Southampton, leads the excavations there. For over 30 years, Simon and his team have used a wide range of ground-based remote sensing tools to map large areas of the site. In many ways, they have rewritten the book on approaches to landscape archaeology for ancient Rome, while their discoveries, such as the function of the boat repair sheds, have cast light on international trade.

  Modern land use has created unusual challenges for them. Today, Portus is a complex place amid a mishmash of modern buildings and mixed-use fields. The central part sits within an archaeological park, but the rest lies outside it, and the amount of planning and detailed work required to map this disconnected landscape is enormous.

  The excavators had been working with ground-penetrating radar (GPR), aerial photographs, and magnetometry so far,40 but not high-resolution satellite imagery. Simon asked if I would like to collaborate. I was apprehensive. Simon is an absolute legend and a lovely human being to boot, and I don’t like to wave imagery at site directors in areas about which I know little or nothing. But he told me he had been searching for a major amphitheater at Portus for years, and to date, had not found it.