Geosciences:

The IGPP Geosciences Research Center, headed by Lars Borg, serves the aims of the IGPP-LLNL in the area of geosciences. This includes managing the geosciences part of the Minigrants program facilitating contacts between UC faculty and students and their LLNL counterparts. The Geosciences Research Center also participates in activities at LLNL by organizing the colloquia, by hosting visitors and collaborators, and organizing workshops. The staff and post- doctoral researchers of the Geosciences Research Center carry out a significant program of research in earth and planetary science as well as analytical astromaterials research on meteorites, micrometeorites, interplanetary dust particles (IDPs), and Stardust samples.

Astromaterials:

Stardust sample analysis: In January, 2006 the Stardust mission successfully returned the first sample of a small body (Comet P81P/Wild 2, ~5 km in diameter) from beyond the giant planets to Earth. The sample was expected to be a “mother lode” of well preserved, ~4.6 Gyr-old materials indigenous to the outer solar nebula environment. The types of materials we had hoped to find were grains formed in the (pre-solar) interstellar medium (ISM) as well as “stardust” grains that originally formed around other stars, survived for up to ~108 years in the ISM and were eventually incorporated into Comet Wild-2 where they have remained frozen for the past ~4.6 Gyr. During the Stardust preliminary examination, we (the community) found that (a) capture damage was worse than expected, (b) the important scientific information is to be found at the nano-scale, and (c) the sample is not what we expected to find in a comet. We recently reported in Science that the Comet Wild-2 sample appears to contain inner solar system materials similar to those found in meteorites (Ishii et al., 2008). (Most meteorites are from the asteroid belt in the inner solar system between the Martian and Jovian systems). LLNL's totally unexpected finding after ~2 years of careful examination of the returned sample essentially redefines the direction of comet science.  

Interplanetary dust research: IDPs are collected in the stratosphere using high-altitude aircraft. They are probably the most cosmically primitive and potentially astrophysically informative extraterrestrial materials available for laboratory investigations. We have a robust program of research on IDPs using state-of-the-art analytical instruments including nanoSIMS, Focused Ion beam (FIB), nuclear microprobe and a newly installed 300 keV SuperSTEM (Matzel et al., 2008). Some IDPs are likely indigeneous outer solar system (in contrast to meteorites that are mostly from the asteroid belt) and a major goal is to identify interstellar material in IDPs and compare its properties with those of dust in the ISM and dust around young stars observed by astronomers.  

Meteorite research: Primitive meteorites offer insights into the earliest processes occurring in the molecular cloud and early nascent solar system. The study of these materials has constrained the timing and conditions under which the first materials solidified, as well as the nature of secondary process by which these materials were modified. Recent work, however, has demonstrated that the chronology based on short-lived radionuclides is far from straight forward, and that fundamental questions of parent isotope homogeneity still exist. Studies to address this issue, as well as related issues of how geochemical and isotopic systematics of these materials respond to alteration processes occurring in the nebula and on parent bodies are of fundamental importance. Using state-of-the-art electron and ion beam methods we are examining some of the earliest solar system solids including CAIs, amoeboid olivine aggregates (AOAs) and refractory metal nuggets (RMNs) opaque assemblages (OAs).

Lunar samples: One of the pillars of lunar research has involved the analysis of samples returned by American and Soviet spacecraft missions in the 1960's and 1970's. This effort has recently expanded through the analysis of lunar meteorites that appear to sample terrain that is not represented in the Apollo and Luna collections. These studies indicate that lunar geologic evolution is even more complex than is suggested from samples collected on the lunar nearside. Two approaches of modern lunar sample science has been to analyze new (meteorite) samples or to employ new generation instrumentation that either allows new types measurements to be completed or facilitates analysis of small, unusual samples that could not be analyzed in the past. Major objectives of this research is to better understand the history of lunar differentiation, the geologic variability of the surface and interior, the role of volatiles in lunar magmatic evolution, and the role of impact processes in shaping the lunar surface.

2008-05-20 | LLNL-MI-404000-REV-1