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2008 Annual Science Report

University of Hawaii, Manoa Reporting  |  JUL 2007 – JUN 2008

Acquisition and Installation of a New Cameca Ims 1280 Ion Microprobe

Project Summary

The University of Hawaii has acquired a state-of-the-art Cameca ims 1280 ion microprobe. It is housed in the W. M. Keck Cosmochemistry Laboratory (Gary R. Huss, Director), which concentrates on NASA sponsored research. In addition to working on astrobiology projects, scientists in the W. M. Keck Cosmochemistry laboratory work on samples returned by the Stardust and Genesis Missions, meteorites, interplanetary dust particles, lunar samples, and other samples of interest to people trying to understand the origin and history of the solar system. The ion microprobe has already shown itself to be a very useful analytical tool and is facilitating and catalyzing interdisciplinary research

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Project Progress

This report covers the second full year of operation of the ims 1280. During this year, we have carried out several projects to measure oxygen isotopes in primitive solar system bodies (Krot et al., 2007; Connolly et al., 2008; Krot et al., 2008a; Makide et al., 2008). Examples of this work are shown in Figures 1 and 2. We also carried out several studies of the distribution of short-lived radionuclides such as 26Al and 60Fe to investigate the chronology of the early solar system (Huss et al., 2007; Krot et al., 2008a; Nagashima et al., 2008; Makide et al., 2008). Deter mining precise isochrons, such as that shown in Figure 3, help to delineate the chronology of the early solar system. We have begun a study of the H abundance in the solar wind collectors returned by the Genesis Mission. And we have been working on understanding the nature and origin of carbon-rich lithic clasts in the Ischeyevo meteorite (see report on Raman microscope). This latter study is the first one in which we used the ability of the ims 1280 to produce isotope ratio maps (Figure 4). With maps like Figure 4, we can investigate the individual phases that contain anomalous material and ascertain their origin.

The first peer reviewed paper containing data from the new ion probe appeared during the last 12 months (Krot et al., 2008b).We also continue to make progress on installing our new solid-state imaging detector called SCAPS. With this new detector, images like Figure 4 can become truly quantitative. Figure 5 shows the housing of the new detector on the text bench. The electronics are nearing completion and we look forward to installing the new detector on the ion probe this fall.

Oxygen isotopic data for some rare FUN inclusion from CV chondrites. We are now able to collect data with sufficient precision to see the details of the isotopic evolution of these inclusions. All started out with compositions at about -50â°, -50â°. While molten, evaporation resulted in mass-dependent fractionation of the oxygen isotopes, moving the composition to the right along the FUN FL line. Later there was isotopic exchange with a reservoir near the terrestrial fractionation (TF) line resulting in a second array for some inclusions and final compositions near 0â°. 10â°. (From Krot et al., 2008)
Oxygen isotopic compositions of CAIs from CR2 chondrites. The compositions are uniformly 16O-rich, which indicates little processing of exchange with external oxygen reservoirs. (From Makide et al., 2008).

Al-Mg isochron from a CAI from the Kaba CV3 chondrite. The new Cameca ims 1280 permits determination of precise isochrons even for objects that do not have particularly high Al/Mg ratios.
This image shows the 15N/15N ratio in delta notation over a 50x50 micron area of a lithic clast in Isheyevo. The big bright spot near the center and four smaller spots of similar brightness are areas of very high 15N/15N ratio (>1.5 x terrestrial), probably produced in interstellar space. We are now working on characterizing these spots mineralogically.

Vacuum housing for the new SCAPS detector on the test bench. The housing will attach to the ion microprobe with a flange at the back right housing. The liquid-nitrogen-cooled detector can be inserted into the beam line via a linear drive with a bellows that can be seen, compressed, in the middle of the housing below and to the right of the liquid nitrogen dewar.