Spectroscopy Spies Extraterrestrial Minerals In 467-Million-Year-Old Limestone

The team included former FMNH postdocs Surya Rout and Xenia Ritter, Research Associate Birger Schmitz (Lund University, Lund, Sweden), and undergraduate interns Katarina Keating and Kevin Eisenstein. The researchers devised a Raman-spectroscopy method (using the Field Museum’s WITec alpha 300R Raman spectroscopy system) to identify extraterrestrial chrome-spinel minerals in limestone excavated from the Lynna River section near St. Petersburg, Russia, and distinguish them from terrestrial minerals. The goal of the study was to identify and analyze extraterrestrial chrome-spinel from sedimentary rock to determine the diversity of sources of these minerals, which include a variety of different asteroid parent bodies including S-type asteroids, Vesta and vestoids. The team found a fundamentally different meteorite flux ~467 million years ago compared to today and other time periods in Earth’s history. They also observed that the grain size range of the samples determines the mix of different sources, i.e., larger grains originate from more thermally altered parent bodies such as differentiated asteroids like Vesta, whereas smaller grains tend to originate from smaller and less altered asteroids. The methodological implications of the study for future research are significant. Application of this method will enable Raman to be used to identify extraterrestrial minerals in sediments of different ages, and together with EDS and oxygen isotopic analysis will enable scientists to determine how the sources of extraterrestrial material that arrives on Earth changes through time. The study was supported by the Field Museum’s Science and Scholarship Funding Committee.
February 9. 2024