Gretchen Benedix is the lead on initial Mineralogy/Petrology of the meteorites found by the Desert Fireball Network. This includes classification and description of the samples. She has nearly 20 years of experience studying, analysing, and interpreting the history of many different classes of meteorites. She will also be involved with retrieval of the samples. She is currently a senior lecturer in the Department of Applied Geology at Curtin University as well as a Research Associate at the Western Australia Museum (Department of Earth and Planetary Sciences).
Gretchen is enthusiastic to be a part of the Australian Desert Fireball Network because it represents a unique opportunity to determine the sources of meteorites. This adds a level of context common in earth-based geology that is not usually available when studying meteorites. This project also allows her to combine her favorite things to do, such as looking for meteorites and camping!
Meteorite-asteroid relationships – working with the Desert Fireball Network, I initially classify and then thoroughly study the meteorites that are found after their fireball is witnessed with the DFN cameras. The study of meteorites with orbits offers more evidence about the relationship between asteroids and meteorites. The combination of knowing the orbit along with the anomalous nature has lead to new thinking about differentiation in the asteroid belt.
Surface geology and mineralogy of Mars – Mars has always peaked the curiosity of Earthlings from ancient civilizations to the present. This is in part because we’ve been able to see its surface throughout history and various observations led to the belief that life might thrive there. Over the past 30 years, numerous missions have focused on the Red Planet using a variety of remote sensing techniques to study the surface and “follow the water”. A possible plan of both the European Space Agency and NASA is to bring a sample back from, as well as to send astronauts to, Mars. Thus, the study of the surface geology of Mars is timely and vital in order to help provide a basis of knowledge to underpin these future missions. I measure the spectral features of individual minerals found in Martian meteorites and use these to interpret remotely sensed spectra from a variety of current space missions to better constrain the surface geology and, thus, the geologic processes (interaction with water, giant impacts, igneous activity) that have shaped the surface of Mars.
Relationship of metal and silicate during core formation on asteroids and other planetary bodies – Current thinking about planetary differentiation is that precursors to planetesimals and planets are chondritic (meaning primitive in both the textural and chemical sense) meteorites. The heterogeneously distributed metal in these types of meteorites is thought to pool and form diapirs, which then sink through a solid, but ductile, silicate mantle to form a core. Am important aspect that has not been tackled adequately is the connection between silicate and metal during this process. This is in part due to the fact that it is difficult to sample the cores of planets and most iron meteorites do not have any associated silicates. To better understand the process of differentiation (and planet formation), I study the trace element chemistry of meteorites for which there is both silicate and metallic material available (primarily primitive achondrites).
Mineral microstructure in meteorites – What does mineral microstructure tell us about different geologic processes? The crystal structure of the minerals that make up meteorites can be used to constrain the environment in which the rocks formed and evolved. Electron-back-scattered diffraction (EBSD) techniques have fairly recently been applied to silicate materials in rocks, however the initial use of EBSD was on terrestrial metallic alloys, where iron meteorites were used as controls on the slow cooling that forms perfect alloys. One aspect of iron meteorite studies has been determining cooling rates of the parent bodies. These cooling rates have been used to place constraints on parent body size (Benedix et al., 2013). An important area that has not been addressed is the fact that traditional cooling rates of iron meteorites are applicable to when the parent body was in a very specific temperature range. Combining the microstructure of iron meteorites and radioisotope dating (ages which represent specific temperatures) will produce a robust method to understand the cooling rate of a particular meteorite over the course of it’s entire temperature regime.
Oxidation state of the solar system – Along with pressure and temperature, oxidation state is fundamental to defining how a geological system evolves. The conditions of the solar nebula played a role in the formation of the materials that condensed from it (Benedix et al., 2005). How did oxygen fugacity affect the condensing material? What affect does it have on the evolution of this material? And finally, how did it vary within the solar nebula? These questions are essential to understanding the evolution of the Solar System as oxidation state controls the dominant mineralogy from which the asteroids and planets were built. One avenue is to study chromite in meteorites, which record the original oxidation state of a planetary body (Ford et al., 2008).