As they travel through space or enter Earth’s atmosphere, meteorites can experience very strong forces and impacts. Those impacts can produce incredible amounts of stress and deformation within meteorites, which can manifest itself as Neumann bands (grey and white image; the Neumann band is running from the top left to the bottom right of the image). Neumann bands appear as thin and straight streaks, and are typically remnants of impacts that occurred in space. When a meteorite that already has Neumann bands is heated up (this occurs only at special temperatures depending on the composition; in this case it was probably around 650 degrees Celsius), annealed Neumann bands can form. So, when you see annealed Neumann bands (blue and yellow image), you know that the meteorite experienced great stress—from an interstellar impact, perhaps—and was also heated up afterward. The Gibeon meteorite samples are not known to have been reheated, while the Karasburg meteorite is known to have been reheated. This helped Brehm realize he had Karasburg meteorite, and not a Gibeon meteorite.
During the annual International Metallographic Society meeting in September 2019, materials science and engineering senior Johnathon Brehm earned the George L. Kehl Award and a $1,000 prize in the International Metallographic Contest for his entry, “Gibeon and Karasburg: A Meteorite Mishap.”
Founded by metallographers George L. Kehl and C.K.H. Du Bose as a way for metallographers from around the world to showcase their skills, the competition today includes five classes. The contest’s goal is to advance the science of microstructural analysis by providing an opportunity for people interested in material properties and characterization to display their work and communicate scientific information.
Brehm submitted a poster unveiling the mystery of his own mislabeled meteorite.
“I purchased a meteorite online labeled as a Gibeon meteorite. After doing metallography and compositional analysis, I realized that none of the features of my sample were matching with the textbook Gibeon meteorite characteristics,” he says. “I knew that the meteorite that I had was recovered near the Gibeon impact, but that there were two other impacts within range. After researching these two impacts, I found that my meteorite matched very well with the characteristics of the Karasburg meteorite.”
The Gibeon meteor fell in Namibia, Africa, in prehistoric times. The Karasburg meteor also fell in Namibia, not that far away—and, notes Brehm on his poster, only a handful of its pieces have been found. Because of their proximity, researchers initially assumed that Karasburg meteorite pieces were just far-flung Gibeon meteorite pieces. More careful analysis, however, revealed their distinct dissimilarities.
And with the analysis of his meteorite, Brehm realized he owned a much more unique piece of history and had a good story to tell. “I had a really interesting project with my meteorite being initially mislabeled, and I thought that I had a great chance at winning first place in my class,” says Brehm. “I also wanted to increase my visibility in the International Metallographic Society and be able to network with current professionals.”
When he graduates in December 2020, Brehm hopes to work in metal forging, casting or a failure analysis consulting company and plans to pursue his professional engineer license. Currently, he represents UW-Madison as the world’s only student representative to the International Metallographic Society, where his goal is to increase student involvement in materials science and engineering and in metallography.
He has been a co-operative education student and an intern at Scot Forge Company of Spring Grove, Illinois, and in summer 2020 will be an intern with MetalTek International of Waukesha, Wisconsin, where he will be gaining experience in centrifugal metal casting. He also is an editor for the Wisconsin Engineer magazine and is vice president of corporate relations for the Wisconsin Engineering Student Council.