STXM search for carbonate in samples of Comet 81P/Wild 2

We employed a Scanning Transmission X-ray Microscope (STXM) to search for carbonate in samples of dust from Comet 81P/Wild 2 collected by NASA's Stardust spacecraft. Although carbonate was not expected in Wild 2 because it generally forms by aqueous processing, which is not thought to occur on comets, we identified two sub-micron carbonate grains in Wild 2 samples. The results demonstrate the effectiveness of the STXM as a search and identification tool for rare minerals that exhibit distinctive X-ray Absorption Near-Edge Structure (XANES) spectra.