Research

The planetary materials research group  is focused on understanding the chemical and physical origins of our solar system and ancient stars. Clues to such origins are stored in the atoms contained within meteorites and related planetary materials (e.g., interplanetary dust particles, as well as cometary, asteroidal, and lunar samples returned from space missions) which are the condensed matter leftover from the time that our solar system formed. We use high-resolution ion-, X-ray-, and electron-beam analytical techniques to extract detailed information on the chemical composition and structure of such samples to decipher the chemical and physical processes that occurred during and prior to the evolution of our solar system. We investigate naturally occuring components in meteorites (and related planetary samples) as well as synthetic analogs. Below are selected representative images from some recent work. Detailed information on this research can be found in the publications.


Investigating the atomic-scale structure of a spinel (MgAl2O4) grain formed in the circumstellar shell around an Asymptotic Giant Branch (AGB) star that existed before the formation of our solar system. The grain (shown in cross section in panel 'a') formed by condensing in a gaseous environment around its host star more than 4.6 billion years ago. The images in panels 'b' through 'f' tell us about the atomic-scale order of the grain and can provide information on the conditions under which it formed. From Zega et al. (2014), Geochimica et Cosmochima Acta 124, 152-169.


 

Analysis of the atomic-scale structure of nanometer-sized iron grains that occur in lunar soils. This is a high-angle annular dark-field image acquired from a transmission electron microscope (TEM). The white dots are columns of Fe atoms in projection. Using TEM and electron energy-loss spectroscopy (EELS), this study analyzed the Fe and showed that some of it occurs as an oxide, rather than as a pure metal. The chemical state of the Fe tells us about how such particles form in lunar soil (a phenomenon known as space weathering) and how it effects the spectral properties. From Thompson et al. (2016), Meteoritics & Planetary Science 51, 1082-1095.


Investigating the chemistry of C-based compounds in primitive meteorites. Panels 'a' and 'b' are TEM images of a small region (scale bars measure 1000 nm) from a carbonaceous-type chondritic meteorite (QUE 97416). Its surface was previously measured using secondary ion mass spectrometry (SIMS), which indicated that the local area of interest shown here contains anomalies in the isotopes of C and H. Using TEM, we located the sub-surface distribution of carbon using X-ray mapping (compare panel 'c' with 'a' and 'b') as well as other elements (panels 'd' through 'i'). Combining these kinds of measurements with X-ray absorption spectroscopy provided information on the molecular chemistry of the C-based material. From Bose, Zega, and Williams (2014) Earth and Planetary Science Letters 399, 128-138.