But the team used imaging software and scanning electron microscopy to analyse these lustrous chunks, about the height of a quarter and several times as wide. They found something far more interesting than the remains of a cookout: homogenised cells and a pitted pattern that proved these fossils started their lives as ancient plants. Using the charcoal, “it is possible to understand a little bit better the scenario of the fire, 75 million years ago,” Dr. Jasper said. With increasingly sophisticated techniques, scientists can reconstruct ancient ecosystems and fire patterns with mounting precision, said Elisabeth Dietze, vice president of the International Paleofire Network, who was not affiliated with the study. She said that molecular markers in charcoal could tell scientists what kind of vegetation burned: For example, rounder, plated molecular shapes indicate woody biomass. In 2010, researchers on King George Island first gathered evidence that ancient wildfires didn’t spare Antarctica. But the samples from that expedition were poorly preserved and researchers could only speculate that the charcoal stemmed from a coniferous tree. Researchers made a more accurate assessment of these new charred remains: They suspect they came from an Araucariaceae, an ancient family of conifers.