Computer Science
Scientific paper
Aug 2006
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006iaujd..10e...1b&link_type=abstract
Progress in Planetary Exploration Missions, 26th meeting of the IAU, Joint Discussion 10, 21-22 August 2006, Prague, Czech Repub
Computer Science
Scientific paper
Genesis returned samples of high purity materials exposed to the solar wind for 27 months, including separate samples of 3 solar wind regimes. Science objectives are to measure solar isotopic and elemental abundances to a precision sufficient for planetary science problems. A crash upon Earth return resulted in massive breakage of collector materials, serious losses of the amounts of materials, and particulate surface contamination. However, atoms are not destroyed by impact. We have over 15,000 pieces of collector materials greater than 3 mm in size. We can show that the implanted solar wind resides safely beneath the surface of the collector materials, while the contamination is on the surface. We have only 100 A of depth margin, but, because we are a sample return mission, we can use all of 21^st century technology to exploit this margin. We were fortunate in that 3/5 materials for dedicated experiments survived in relatively good shape. A major issue is the extent to which the acceleration of the solar wind has modified elemental and isotopic abundances from the photospheric values. Spacecraft studies show that elements with first ionization potential (FIP) greater than 9 eV are depleted in the solar wind relative to lower FIP elements, but the lower FIP elements, which make up most of terrestrial planet material, appear unfractionated. Our preliminary Genesis Fe/Mg is 0.78 and in good agreement with both spacecraft data and the photospheric absorption line ratio. Little is known about isotopic fractionation in the solar wind, but our regime samples represent materials formed by different solar processes. The isotopic compositions of Ne and Ar in the different regime samples agree with permil level precision. There is no evidence for isotope fractionation in the solar wind relative to the photosphere. A sample of bulk metallic glass (BMG) which etches uniformly with nitric acid vapor was recovered intact. This sample provides a check on the presence of higher energy (SEP) solar ions with different isotopic compositons. Extensive lunar sample analyses indicated an SEP 20Ne/22Ne ratio of 11.4 compared to 13.7 for the solar wind. BMG etching produced a continuously dropping 20/22 ratio down to at least 10.8. The trend matches exactly what is seen in lunar samples; however, the trend can be quantitatively reproduced by allowing for the differential implantation of 22Ne and 20 Ne, and differential implantation appears to explain the lunar results as well.
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