Geologists first assembled these clues in the 1990s, announcing discovery of the crater in 1997. .
"We eventually found a pattern in the rocks that showed us when we were right where the edge of the crater was," said Leif Tapanila, a paleontology professor at Idaho State University and co-author of the new study. "You could effectively put your foot on that margin."
"It's a detective story," said Tapanila. "We're using our tools to read the rocks and piece the crater back together.