And while that discovery is novel enough to please any scientist, it's the implication that those perfectly preserved plants may suggest that really excites him.
Thompson, a professor of geological sciences at Ohio State University and a world-class glaciologist, has made nearly annual pilgrimages to Peru's Quelccaya ice cap to monitor its slow demise, a probably victim of recent global climate change. The glacier is retreating 40 times faster now than it was when the first aerial photographs were taken in 1963.
He told this story today as part of his Emiliani Lecture presentation at the annual meeting of the American Geophysical Union in San Francisco.
In 2002, he and his colleagues from the Byrd Polar Research Center had found a small bed of plants that had, until then, been buried by the ice cap. Carbon dating on those plants suggested that they had been buried nearly 5,000 years ago.
"We were surprised by those dates and had the plant tissue dated four times by two separate institutions," Thompson said, "but the dates remained the same."
This time, Thompson decided to look up a different valley, some 1.8 miles (3 kilometers) from the initial plant find. "But about a quarter-mile from there, I found yet another area of uncovered plants."
When Thompson returned to his campus lab, he packaged the three new samples and sent them off for carbon-dating as well. The first two yielded dates similar to the 2002 plant find -- about 5,200 years ago.
But the date for the third plant sample seemed radically skewed.
"We had the samples dated at the National AMS Facility at Woods Hole Oceanographic Institute (NOSAMS) and later sent other samples to the Lawrence Livermore National Laboratory (LLNL)
Contact: Lonnie Thompson
Ohio State University