This is a continuation of our previous and ongoing efforts to accurately determine abundances and isotopic composition of noble gases in solar wind delivered by genesis mission and spallogenic neon…

This is a grant awarded by the National Aeronautics and Space Administration (NASA) to The Washington University in St. Louis, Missouri for continued research related to analyzing the composition and isotopic signatures of solar wind and cometary dust samples returned by the Genesis and Stardust space missions. The $1,109,974.22 grant supports the development and optimization of specialized mass spectrometry instrumentation and techniques to improve the precision of measurements for rare noble gas isotopes. Specifically, the research aims to resolve uncertainties around the origin of the enigmatic "Phase-Q" component in primitive meteorites, which may have implications for understanding the chemical evolution of the solar system. This grant represents a continuation of the university's longstanding involvement in analyzing samples from NASA's sample return missions through the Laboratory Analysis of Returned Samples (LARS) program. No set-aside designation is indicated for this award.

This is a continuation of our previous and ongoing efforts to accurately determine abundances and isotopic composition of noble gases in solar wind delivered by genesis mission and spallogenic neon and helium in sub-micron cometary grains in the outermost layer of the aerogel collector flown on NASA's stardust mission. Over previous years we developed a customized 8-multiplier mass spectrometer (in collaboration with NU instruments) and refined a laser technique for extraction of solar wind noble gases from CM-size genesis collectors with depth profiling capabilities. The most abundant isotopes 36-38AR, 82-86KR and 129-136XE are now measured with permil precision, but the precision of low-abundance 78-80KR and 124-128XE is not yet sufficient to solve isotope cosmo-chemistry problems. One of these problems is the origin of the enigmatic phase-q, a minor fraction of primitive meteorites containing most of the planetary heavy noble gases. The isotopic composition of XE in phase-q can be approximated by linearly fractionated solar XE with the addition of either XE-HL (presumably from presolar nanodiamonds) or from 244PU fission modified by isotope-specific chemical fractionation. In the latter case the origin of phase q is seemingly local rather than presolar . With the present precision of 124-128XE, both hypothesis have statistically indistinguishable likelihoods. But triple or even double the analytical precision for light solar wind XE isotopes will allow US to determine which one of the two hypotheses is likely to be correct. We already have been allocated the solar wind collectors required to improve XE counting statistics by factor of 2. We made all necessary preparations to estimate BR abundance in the solar wind using the 79BR(n, gamma)80KR reaction. According our examination of various neutron irradiated genesis solar wind collectors, only pure uncoated sapphire (SAP) has an acceptable level of terrestrial BR contamination. We already have in our possession ~ 5 SQ. CM of SAP, acquired reliable BR standards and discussed all details of time-split neutron irradiation with the missouri research reactor, our neighbor and long-term collaborator. The multicollector mass-spectrometer noblesse will be optimized for measurements of small excesses of BR-derived 80KR on top of solar wind KR in neutron-irradiated SAP. The first in the US, our new helix-MC+ mass-spectrometer is the only instrument in our lab capable of resolving doubly charged 40AR ++ from 20NE+. After certain required modifications and assessing the reproducibility, pressure dependence and actual systematical and statistical errors, we will use our helix-MC+ for independent verification of (1) light solar wind noble gases to resolve the existing controversy in SW-NE composition measured in zurich, minnesota, and our lab; and (2) our earlier finding of spallation 21NE in track-free aerogel flown on the stardust mission. The latter will be complimented with the study of major target elements (MG, AL, SI) in track-free aerogel at ALS facility at lawrence berkeley national laboratory carried out by our collaborators ryan ogliore and andrew westphall. The 21NE irradiation record may lead to an estimation of the comet erosion rate before IT is perturbed into the inner solar system. We have 10+ years experience in analyzing solar wind noble gases delivered by genesis, dedicated mass spectrometers, and customized laser extraction facilities to fulfill the goals of the proposed study which is in line with the goal of the lars program to maximize the science derived from planetary sample-return missions through the development of laboratory instrumentation and/or advanced techniques required for the analysis of returned samples and direct analysis of samples already returned to earth .