Nitrogen is one of the many chemicals bodies release as they decompose. It’s also an essential mineral for plant growth. The change in soil chemistry from extra nitrogen could alter the chemical signature of the plants growing over the grave. As a result, thought Mundorff, those plants might reflect red and infrared light differently enough to be picked up by satellites measuring Earth’s vegetation. Although the satellite sensors themselves provide only a few points of data per square meter and might not pick up small graves containing a single body on their own, the data they collected might be useful when combined with additional information from LIDAR.
A year and a half after the burial, the grave was covered with grass. The nitrogen levels in the leaves over the graves skyrocketed to five times greater than those in the leaves over the undisturbed soil. The preliminary data supported Mundorff’s hypothesis that buried bodies affected the vegetation growing over them.
Back in Knoxville, with the fence in place by the closing days of 2012, Mundorff finally got the green light to start her original LIDAR-based research idea. Around Valentine’s Day in 2013, Mundorff and a handful of students broke ground at the new site, a wooded bluff on the Tennessee River, opposite downtown Knoxville. Among the students was Katie Corcoran, who recently joined Mundorff’s project after working with the Seminole tribe in Florida, using LIDAR and historical aerial photos to find archaeological sites.
The team dug into the earth, dark and streaked with tawny-colored clay, with shovels and pickaxes. They carved out four graves for 10 donated bodies. One grave holds the remains of six people; another contains three; and another fits a single body. The fourth grave, dug to the same dimensions as the six-person grave and refilled, would be the control.
For the next several months, Mundorff and Corcoran’s team scrutinized the site in almost every way. A photographer documented the graves as they settled. A botanist surveyed the vegetation and mapped its regrowth. A scientist from the nearby Oak Ridge National Laboratory (ORNL) set up thermal cameras to record the temperature of the graves over 24-hour periods while the bodies decomposed. As the seasons shifted, grasses and shrubs reappeared. Mundorff and Corcoran snipped leaves and tucked them into envelopes so they could analyze their chemical composition.
On a crisp November day in 2014, I joined Mundorff and Corcoran at the burial site. Two fences hemmed in the allotment. Mundorff first unlocked an 8-foot-tall chain-link fence topped with razor wire, then an equally high wooden privacy fence, and swung open the gates. Leaf litter from oak and maple trees covered the ground and crunched beneath our boots. Days of rain had left the clay-rich soil soft.
Metal disks stamped with letters and numbers, and nailed to stakes in the ground, identified the graves. Without the markers, they would have been easy to miss.
Remote Sensing Symphony
The next day, the three of us met in Mundorff’s office for a sneak peek of the next phase of the research. The space is a cinder-block box with high ceilings and fresh blue paint on the walls, buried beneath the university stadium. Bones and other artifacts sat atop bookshelves and tables, and a poster of Van Gogh’s painting of a skeleton smoking a cigarette hung on a wall.
Corcoran loaded onto her laptop LIDAR images collected before the burial. Eight million points populated the screen in a dense 3-D image called a point cloud, showing streets, buildings and hills. With a few clicks, she zoomed in to the site and stripped away vegetation to reveal the contours of the bare earth.
Corcoran switched to a satellite image also taken before the burial. It looked like a photograph, but it was a composite of several spectral bands, each measuring the reflectance of the surface at different wavelengths of light. She highlighted the vegetation by selecting the infrared band. Knoxville’s wooded areas and fields glowed red.
These “before” images provide an important baseline that Corcoran and Mundorff can use to compare against the data they’re collecting through spring 2016. They’ve enlisted the help of Devin White, a remote sensing expert at ORNL who has used airborne and satellite imagery to identify ancient footpaths threading through the Sonoran desert between Arizona and Mexico. White will merge the data streams taken from the ground, air and space, and use it to spot locations of interest. “If each layer is an instrument, how do you get them to all play together and do something more than the sum of their parts?” asks White. “You have to turn it into a symphony.”
The week is marked by the arrival of a $200,000 ground-based LIDAR scanner, on loan from the Remote Sensing Center at the Naval Postgraduate School in Monterey, Calif. Although Mundorff’s goal is for investigators in the field to use aerial LIDAR, the ground-based unit’s data — along with existing aerial and satellite imagery — will help White’s computers at ORNL learn what a hidden grave looks like.
Mundorff has faced several challenges during the project and admits there is still a lot of work to do, but she remains hopeful that she can develop techniques that will help find the missing, and potentially bring their killers to justice. She may have stopped doing forensic casework, but she remains devoted to developing tools for those who continue to do the difficult work. “I’m a practitioner at heart,” she says. “All my research is about the practice of forensic anthropology.”
[This article originally appeared in print as "Body of Evidence."]