Probing hydrous phases on Mars using martian meteorites

点击翻译按钮获取中文摘要

Mars has long been the primary target in the search for possible life beyond our planet, mainly due to widespread evidence that water once flowed on its surface. Water is an essential ingredient for life on Earth, but the identification of water alone is not enough to determine if the ingredients necessary for life were once present. Without a habitable climate, and bioavailability of phosphorous (as an essential component in the building blocks of life such as DNA and RNA) it is unlikely that life on Mars could have had the chance to evolve. Our specific aims are: 1) To study hydrous Martian phosphate minerals in melt inclusions using correlative structural and chemical observations of D/H, H2O, and OH on the nanoscale using Scanning Transmission Electron Microscopy (STEM), and Atom Probe Tomography (APT). 2) To determine how sulfur isotopes (used as tracers of atmospheric processes on Mars) have been disturbed within Martian sulfide minerals during shock metamorphism using nano Secondary Ion Mass Spectrometry (NanoSIMS). 3) To determine if Martian atmosphere was incorporated into shock-melted sulfide minerals during ejection from the Martian surface. If successful, this project will greatly strengthen efforts to constrain when and how the ingredients for life on Mars. Two such mineral groups - phosphates as one of the only OH-bearing minerals in Martian meteorites, and sulfides are the focus of this study. The analysis of Martian meteorites is complicated since all Martian meteorites are inherently `shocked', undergoing intense deformation during ejection from the Martian surface before landing on Earth. These shock events can cause deformation, mineral transformations, and chemical reactions including the incorporation of Martian atmosphere into certain minerals and glasses through shock compression. The effects of shock metamorphism are so extensive that isotopic heterogeneities are often induced at the nanoscale, complicating efforts to accurately characterize Martian materials with conventional techniques. Resolving these nano-scale heterogeneities is central to our goals. The correlative STEM and APT approach is only accessible to us through EMSL, and has proved invaluable for target selection for APT analysis. Additionally, NanoSIMS will be used to help resolve isotopic heterogeneities within sulfides. If successful, this project will greatly strengthen efforts to constrain when and how the ingredients for life on Mars, and potentially throughout the Solar System, may have existed and evolved. Answering these questions will allow for a more accurate prediction of phosphorous and water availability for life on Mars, the origin of Martian water, and the evolution of the Martian atmosphere which are especially important when interpreting analyses of Martian minerals that contain isotopic signatures of atmospheric and water interactions.