A spooky sounding technology is finding old, unmarked graves. Using hyperspectral imaging, scientists from McGill University have found unmarked animal graves with special cameras that measure changes in the light coming from soil and plants.
Hyperspectral imaging collects and processes light from across the electromagnetic spectrum, including visible light as well as ultraviolet and infrared light. The research could help police solve missing persons cases or reveal new mass graves from hundreds, if not thousands, of years ago.
"As soon as there is some decay you can see a difference," said Andre Costopoulos, a professor at McGill University developing new techniques to find old graves.
"We suspect that some of these graves are over 40 years old, and are excited to try to find much older grave sites," some of which could be hundreds of years old, said Costopoulos.
The McGill project began in an unlikely place: an African animal safari park in Quebec called Parc Safari. Parc Safari officials wanted to exhume a buried elephant and reassemble the bones for an park exhibit. But the park official didn't know where the dead elephant was buried.
Costopoulos was enlisted to find the missing elephant. Over three seasons Costopoulos' team found seven animal graves at depths of two to three feet deep (including the elephant). They knew more animal graves existed at the site.
Meanwhile, Margaret Kalacska, another professor at McGill University, was studying the effects of soil on plant growth by measuring the amount of chlorophyll in plant leaves using hyperspectral imaging. Kalacska and Costopoulos decided to combine their expertise to find the remaining animals at the pet cemetery.
The McGill scientists borrowed a plane from the Canadian National Research Council and equipped it with two cameras. One camera recorded light in the visible spectrum and into the infrared range. The other camera recorded light in the infrared and longer light ranges.
When the hyperspectral camera-equipped aircraft flew over the animal graveyard, the scientists found all seven known graves, plus 25 new graves, some of which were buried up up to eight feet deep.
"One flyby of the aircraft gave us four to fives times more information than we gathered in three seasons of digging," said Costopoulos.
For the first five years or so a decaying body inhibits plant growth. "Initially it's a pretty toxic environment," for plants, said Kalacska, who, along with Pablo Arroyo and Tim Moore, manages the technological side of the research. Plants that grow over such recent graves don't reflect as much light in the visible and near infrared region, which scientists can detect using their cameras.
After five years, however, the plants growing over buried body suddenly reflect light instead of absorbing light. In fact, on-grave plants reflect more than twice the green light of off-grave plants. For a human eye detecting such tiny changes would be "very hard," said Kalacska, but the difference is obvious to the hyperspectral camera.
The increase in reflected light comes from an increase in chlorophyll, the pigment that plants use to convert light from the sun. After five years a decomposing body becomes fertilizer, supplying the growing plants with much needed nutrients like nitrogen and phosphorus. Bigger plants with bigger, healthier leaves reflect more light.