Status and Science Results D. S Burnett and Genesis Science Team GPMC, Feb 2009

1. Status and Science Results D. S Burnett and Genesis Science Team GPMC, Feb 2009

2. Slides Background/Review Material 3-10 Ne Assessment of Concentrator Performance 11-14 O isotopes 15-18 N isotopes 19-30 Noble Gas elements and isotopes 31-37 Elemental Abundances 38-54 Solar vs solar wind abundances 55-57 Contamination Issues 58-67 Status/Summary 68-72 Contents

3. What: Mission in a Nutshell • Placed a spacecraft outside the terrestrial magnetosphere • Exposed Materials • Solar wind ions (keV/amu) implant and stick • Exposed for 27 months • Fluences low, so materials must be ultrapure. • Returned materials to Earth for analysis in terrestrial laboratories.

4. Why: Genesis Science Objectives • Provide solar isotopic abundances to level of precision required for planetary science purposes. • Provide greatly improved knowledge of solar elemental abundances. • Provide a reservoir of solar matter to meet the needs of 21st century planetary science. • Provide elemental and isotopic data for the 3 different types (“regimes”) of solar wind.

5. Solar Wind Regimes • Three different kinds (“regimes”) of solar wind: • High speed (coronal hole) • Low speed (“interstream”) • Coronal Mass Ejections • Genesis separately sampled each of 3 solar wind regimes as well as bulk solar wind: • Allows correction for differences in composition between sun and solar wind • Agreement in derived solar composition from different regimes validates correction procedures

6. BMG Regime Arrays Al kidney Au kidney Concentrator Canister Cover & Array

7. Canister and Collector Materials pre launch target grids regimes Collector arrays Al kidney (PAC) Thermal closeout

8. Analysis Overview • Genesis sample analysis/testing is proceeding on a broad front in 28 laboratories worldwide. • Rates vary, but progress is being made. • The goal of Genesis is quantitative data; great emphasis on getting numbers right. • A major advantage of sample return missions is that important data can be verified, and in most cases, replicated with different techniques. • A major effort has been to make accurate, replicated measurements of the fluences of Mg and Ne. Most techniques can analyze one of these elements, which will then constitute primary quantitative reference fluences for other elements.

9. Analysis Overview, con’t Two distinct requirements: • Extract implanted solar wind from collector materials. • Analyzed extracted solar wind. Can mix and match approaches for extraction and analysis. Mass spectrometry is the most widely-used analysis technique.

10. Science Team Analysis Methods Secondary IonMass Spectrometry (SIMS) Solar wind extracted by ion beam sputtering Gas SourceMass Spectrometry Extraction by laser ablation or chemical etching (HNO3, Hg) Resonance Ionization Mass Spectrometry (RIMS) Extraction by ion beam sputtering Total Reflection X-ray Fluorescence in-situ analysis; unique in not requiring extraction. essentially non-destructive. Inductively-coupled Plasma Mass Spectrometry Extraction by differential chemical etching Accelerator Mass Spectrometry Extraction by differential chemical etching. Radiochemical Neutron Activation Analysis Extraction by differential chemical etching.

11. In-flight Concentrator Performance from analysis of Au cross. (V. Heber et al; LPSC 2009 abstract) Recovered Targets and Holder Au cross held targets in place Ne can be measured on 100 micron size spots by laser ablation. Data for all 4 arms agree. Very important: no azimuthal SW inhomogeneities in targets.

12. Ne analyses of SiC Concentrator Target • The Ne analyses of the Concentrator Au cross have been very important, but to enable a correction for Concentrator isotopic fractionation of O and N, the lack of complete agreement between the theoretical and measured Ne profiles must be understood. • The disagreement may not be due to uncertainties in the modeling because of the limitations of the Au cross as a target material. • Significant backscattering corrections are required and these must allow for the effect of non-normal incidence of the ions. • Heber et al (LPSC 2008) found that the TRIM backscattering model overcorrected the independently-known Ne fluence for collector array AuoS samples. • The Au cross surface is rough. An mplant experiment was carried out to test the TRIM calculations for non-normal incidence and to measure the surface roughness effects (next page) • Ne implants with 20Ne/22Ne = 10 were made into Au cross flight spare material (AuSS), AuoS (smooth Au on sapphire), and diamond-like C (DOS)at 0, 45, and 55 degrees angle of incidence. • The DOS is a control in that Ne backscattering from C is negligible

13. Heber et al., LPSC(2009) Grey =measured; red = SRIM-corrected. amounts of Ne slightly overcorrected by up to 4%. Isotope fractionation with angle relatively small and SRIM corrections OK. c,d) Losses and isotope fractionation larger from Auss due to rough surface. SRIM does not treat rough surfaces. Pattern of losses does not vary smoothly with angle. Accurate correction of O isotopes based on Ne data from flight Au cross will not be accurate.

14. Ne analyses of SiC Concentrator Target A measurement of the Ne fluence on a Concentrator target is required. • Only sub mm areas are required. • The Allocation Committee has approved the transfer of the 60001 SiC quadrant used for O analysis at UCLA to ETH Zurich for Ne analysis. • A single Ar isotopic measurment may be made to verify results from Nancy which show that the Concentrator quantitatively collected Ar ions. • This would be very important in demonstrating that Si and S isotopes can be measured on the Concentrator target.

15. Solar Wind O profile in target SiC. UCLA MegaSIMS. (McKeegan, et al. LPSC 09 abstract) The MegaSIMS is a Genesis-dedicated instrument. The front end is a standard SIMS instrument in which 15 keV O- ions are produced by sputtering of the SiC sample. However, instead of just measuring the low E secolndary ions, they are instead accelerated to 0.5 MeV. The acceleration destroys all interfering molecular ions, in particular the 16OH interference at mass 17. After acceleration, the ions are mass-analyzed and counted with standard accelerator mass spectrometry techniques. Xylene cleaning produced 150 micron areas free of particulate contamination. Residual molecular surface contamination was removed by sputter cleaning with low energy (5 keV) Cs. This produces an acceptable loss of about 21 nm, but results in the clean SW profile shown. Instrumental background was reduced to an acceptable level by a cryo-pumped vacuum of about 3e-11 torr.

16. McKeegan et al LPSC 2009

17. Implications from MegaSIMS preliminary result We have a clear solar wind signal, background corrections are tolerable. Additional data by time of LPSC. The Sun appears to be enriched in 16O by ~60 ‰ relative to Earth and bulk meteorites • Potentially large systematic errors have yet to be properly evaluated, however all should be mass-dependent. • Genesis data well resolved from terrestrial mass fractionation line. • Sun is different from Earth • Sources of mass fractionation: • MegaSIMS (next page) • concentrator optics • see section on Ne in Au cross. • backscatter from target • small; calculated by SRIM • solar wind acceleration • see section on SW isotopic fractionation. • gravitational settling in photosphere • not easy to address, but no evidence that this is important.

18. MegaSIMS mass fractionation • Present instrumental mass fractionation corrections based on terrestrial magnetite of know isotopic composition. This is not exactly correct, but uncertainties hard to estimate. • The ideal mass fractionation standard is an O implant into SiC with an independent, accurately-known 18O/16O. • An implant of the 16O18O (mass 34) molecule has been carried out. • The nominal ratio is 1 set by the mass number. • Small contributions from the tails of 16O16O from mass 32 in the ion implanter will be monitored by measuring the shape of the mass 32 peak and calculating the contribution at mass 34. • An alternative approach is to use a SiC implant with the 18O/16O ratio measured by laser fluorination at UCSD.

19. The isotopic composition of N shows wide variations in solar system materials. Focus here on Earth-Jupiter difference. Mars atm.

20. N isotope analysis status • This is our #2 measurement objective. • Samples of Au-on-sapphire (AuoS) have been allocated to two laboratories: • U. Minn (release and analysis of N2 by room temperature amalgamation) • CRPG Nancy, France (laser depth profiling with analysis of N2) • more details on following slides. • Nancy also allocated “Au cross” frame from Concentrator target holder. • Distinctly different analysis techniques are being used, so if consistent results can be obtained, great confidence can be attached to the results.

21. Nancy (B. Marty) measurement of 15N/14N • Approach is laser ablation of AuoS or Au cross from concentrator target holder. • Implants show release of N as N2 with 100% yield. • Ne measured as control element in flight samples; allows partitioning of measured N in terms of terrestrial contamination and solar wind. • Multi step extraction: laser ablation depth profiling. • 1st steps should remove any N from particulate contamination. • Depth profiling is carried out varying the number of laser pulsesin a controlled manner. • Maxmize SW recovery relative to background contamination by following release of solar wind 20Ne. • Ablation stopped prior to reaching Au-sapphire interface avoiding this source of contamination N. • Brown stain removed by uv ozone in collaboration with Open U (S. Sestak). • Procedural blanks at 10% solar wind levels, which is good. • Impurity level of N in both materials is a serious problem. • Au cross has more solar wind N but also more impurity N, • net improvement in precision, though. • Details in following slides.

22. Marty et al LPSC 2009 abstract Concentrator has gradient of Ne (see slide 11) which causes observed variations.

23. Au cross data have highest proportion of solar/background N With new data, and especially a revised Ne/N SW ratio, results consistent with Sun = Jupiter, rather than Sun = Earth. Calculated mixing line for samples with mixture of terrestrial and Jupiter N x-axis is calculated fraction of solar wind N relative to impurities in sample. Impurity levels are high in Au cross material, so SW fraction is low

24. Minnesota (Pepin, Schlutter, Becker) LPSC 09 abstract • Analysis based on room temperature amalgamation of Au on sappphire (AuoS) collectors with release of N2 gas for mass spec analysis. Ar measured as control elements. • Technique is inherently low blank and insensitive to particulate contamination. • Brown stain interferes, but removed by O plasma cleaning. • Low blanks from cleanup line.

25. Pepin et al LPSC 09 Amalgamation of flight spare control AuoS gives blank levels that are much less than the predicted solar wind fluence and much less than observed either by pyrolysis or laser ablation. Difference is that amalgamation doesn’t release organic N as N2.

26. Minnesota (Pepin, Schlutter, Becker) LPSC 09 abstract • Problem has been incomplete N recovery from flight samples relative to 36Ar. • Based on expected solar wind N fluence, 10/13 samples give essentially 0 solar wind N yield. • Data for 3 samples with N yields > 10% shown in figure. • 36Ar recovery typically 60-70%; 40870 is an exception. • plasma cleaning may leave SiO2 residue, but removal of residue with HF etching doesn’t improve yield.

27. Minnesota (Pepin, Schlutter, Becker) LPSC 09 abstract Measured 36Ar fluences can be converted to 20Ne using independently-measured 20Ne/36Ar. Derived 20Ne/14N agrees within errors to ratio derived from spacecraft instrument data. Data indicate an enhancement in 15N compared to Earth. This is opposite sense of Nancy data discussed earlier. Differences yet to be resolved.

28. Resolution of Low Amalgamation Yield Issue Two Sources of Low Yield: I. Diffusion loss of solar wind N II Release as species other than N2 Mass spec analysis requires molecular N2. Yields of 15N implants good; something special about flight samples. I. The amount of 15N released as a function of temperature in a stepwise heating experiment can be inverted to give a diffusion coefficient. • New custom-designed implants are planned. II Mass spectrometer searches for other N-bearing species negative, but binding in non-volatile N compound can’t be ruled out.

29. Plan B for N • Analyses at both Nancy and, to a lesser extent, Minnesota have been limited by high amounts of N impurities in Au collector materials. • This possibility was anticipated in mission planning, and 1/4 quadrants in Concentrator target contained a Sandia diamond-like-C (DOS) sample from which N should be analyzable by stepwise combustion or possibly by SIMS. • This quadrant was broken in the crash, but most pieces have been recovered (see Alton et al LPSC 09 abstract). • Stepwise combustion efforts are underway at Open U (England) and U. Minnesota. • Prelaunch tests at Minnesota had shown ≈ 50% recovery on 15N implants , but 2008 OU experiments did not recover 15N until the Si substrate of the DOS was dissolved away. This discrepancy remains unresolved.

30. Plan B for N, con’t SIMS isotopic analyses in collector array Si and DOS samples have failed. • With the indication of Jupiter-like N in the revised Nancy data, it was important to try. SIMS sensitivity is adequate. • Impact mixing effects prevent SIMS solar wind N analysis in the first 500 A; instrumental background dominates at depths beyond 1500A, but for 500-1500 A solar wind dominates under good vacuum conditions of CalTech 7f instrument. • Distinguishing between terrestrial and Jupiter-like N potentially feasible. • With Si, 15N measured as 28Si15N+ at mass 43, but much larger amounts of 29Si14N cannot be mass-resolved. • Measurement from DOS should be feasible, as 12C15N- is resolvable from all known interferences, but a surface-correlated interference of unknown origin is present, even on control samples. • Problems encountered with the 7f should be much less using the UCLA MegaSIMS and using concentrator SiC.

31. Heavy noble gas analyses on the Polished Al Kidney (PAC) Wash U This large piece of polished Al was added to the part of the canister surface exposed to the solar wind once the collector arrays were deployed. (See slides 6 and 7). The anticipated use was to provide large area samples for heavy noble gas (Ar, Kr, Xe) analysis. Prelaunch blanks of bulk samples indicated that if a thickness of less than 0.5 micron were analyzed, the levels of ArKrXe contamination were not significant compared to the solar wind. Cube is 1 cm in size.

32. Ar Kr Xe analyses (Wash U) Meshik et al LPSC 09 abstract Simultaneous measurement of the two Ar isotopes gives high precision isotopic ratios.The instrument can measure up to 8 isotopes simultaneously.The power level of a uv ablation laser was adjusted to remove only a small amount from the surface, and the solar wind Ar isotopic composition measured with each step in the release. The decreasing 36Ar/38Ar ratio results from isotopic fractionation during implantation and is expected.The average is different from the Earth, as reported previously.The successful SW Ar depth profiling points the way for similar experiments on Kr and Xe which will minimize the effects of surface contamination.

33. Meshik et al LPSC 09 abstract: Kr depth profile Individual points represent steps in laser ablation depth profile, as shown in previous slide. Constant 36Ar/84Kr ratio not expected as Kr depth profile deeper. Earliest steps with low 36Ar/84Kr represent air surface contamination.

34. Meshik et al LPSC 09 abstract: Xe depth profile Individual points represent steps in laser ablation depth profile. The 84Kr and 132Xe depth profiles are sufficiently simukar As was previously known from meteorite studies, the solar wind Kr/Xe ratio is much less than that in the terrestrial atmosphere. Blank corrections on the data are still required, but a firm constraint is that: 84Kr/132Xe ≤9.71 There are no true photospheric abundances for noble gases. The Anders & Grevesse abundance compilation gives 84Kr/132Xe = 20.7. The difference would be consistent with FIP fractionation, but this would be larger than expected.

35. Vogel et al (ETH Zurich) LPSC 09 Abstract Single step laser ablation analyses of bulk solar wind ArKrXe from CZ Si. Results are compared with closed system etching data of lunar ilmenite (YLR) from a lunar sample of low cosmic ray exposure age, with the terrestrial atmosphere (TA), and with estimates from “solar” abundance compilations. (There are no photospheric abundance data for noble gases). These Genesis data agree with those from Wash U on previous page. Terrestrial atmospheric noble gas data have long been recognized as not representative. Except for 36Ar/84Kr, the Genesis and lunar regolith data agree, but alternative interpretations of the ilmenite etch data (dotted line) are possible. If the 84Kr/132Xe Genesis- “solar” differences were a FIP effect, then a similar difference in 36Ar/84Kr would be expected. We may be into “physics beyond FIP”

36. Light noble gas diffusion loss in Al collectors.Mabry et al LPSC 2009 abstract. Flight samples of polished Al (PAC) and Al on sapphire (AloS) were heated at 6 different temperatures for 322 days. Ne and Ar isotopic ratios were unaffected by heating, but large 3He/4He decreases were observed (figure). A badly scratched AloS sample (063) shows a 9% decrease in 3He/4He and a 25% decrease in 4He/20Ne relative to the much less scratched 070 sample. This is somewhat surprising as scratching should remove all solar wind and not affect elemental or isotopic ratios. Plotted points are sum of all pyrolysis steps.

37. Mabry et al LPSC 2009 abstract. Laser depth profiling data on heated and unheated flight AloS samples. Fractionation during implant causes the 3He/4He to decrease with depth as shown by the theoretical curve (TRIM). Preferential thermal loss of 3He causes the profile to flatten as shown by the blue curve. Because loss is preferential from shallow depths, the results from the deepest depths (650oC) are unaffected by heating. The difference between the laboratory unheated 070 sample and the TRIM profile can be interpreted as reflecting the incomplete SW He retention in AloS. But it also appears that the TRIM curve is dropping too fast at larger depths.

38. Science Issue: Do Sun and solar wind have same elemental composition? Slides 39-42 are background, unchanged from earlier GPMC. • Spacecraft data have shown that high first ionization potential (FIP) elements are depleted in solar wind compared to solar surface (photosphere). • e.g. Fe/He is higher in SW than in photosphere. • Data for most easily-ionized elements (FIP < 9eV) appear unfractionated. • Most of elements in terrestrial planets have FIP<9eV • Genesis will provide a better test, but never will escape need to know a few photospheric elemental ratios accurately. • If fractionations due only to first ionization potentials, solar wind and photosphere isotope ratios expected to be same.

39. Fractionation Factor F = (X/Mg)SW / (X/Mg)photosphere

40. FIP Plot from spacecraft data

41. FIT (first ionization time) plot from spacecraft data FIT is an estimate of the time required to ionize a neutral atom upon transport from the lower temperature photosphere into the solar corona, from where the ion will be accelerated and incorporated into the solar wind. FIT is more physical than FIP, but is model-dependent. Data plots using FIT are cleaner than those with FIP with the 9eV fractionation cutoff (translated to about 20 sec ionization time) showing clear depletions of high FIP/FIT elements.

42. Fe/Mg analyses by SIMS (Jurewicz et al., ASU) • Details of analyses in Nov. 2007 GPMC; not repeated here. • Major discrepancy in Mg fluence between Si and DOS (Sandia) when “external” implant standard used. • Discrepancy eliminated by implanting known fluence of 25Mg as internal standard into flight samples. • Unlike Mg, good agreement for Fe fluence obtained between two materials.

43. Comparison with photosphere and spacecraft Fe/Mg(next two slides unchanged from Aug 2008 GPMC) All data sets agree within errors of other data. No evidence for FIP (FIT) fractionations. Both Fe and Mg have FIP < 9 eV.

44. Compare with CI chondrites Most compilations of “solar” elemental abundances based on CI chondritic meteorites. Justification for this is agreement with photospheric abundances. Genesis Fe/Mg, at present, distinct from CI ratio, but systematic errors in implant fluences must be assessed before final conclusions drawn. Goal will be to maintain precision as on figure, but Fe/Mg value could change.

45. Plan to check Mg/Fe implant fluences • One set of Fe implants are available (Kroko 2005). • 3 separate implants: 56Fe at 5e15/cm2, 56Fe at 4e13/cm2, 54Fe at 2e13/cm2. • SW fluence data on Sandia (diamond-like-C), SoS, and Si. • Fluence can be independently analyzed accurately on the 5e15/cm2 Si implant by isotopic dilution using ICPMS (FSU). • Accurate measurement of high fluence implant in one material applies to all materials in same implant. • Sandia data based on 4e13/cm2 implant but accurate measurement of relative fluence measurement by SIMS of 5e15 and 4e13 Sandia implants is possible (ASU, CIW). • High fluence implant also calibrated by RBS (ASU). • RBS data agree well with ion implanter fluence. • Also show that fluence uniformity to better than 1%.

46. Plan to check Mg/Fe implant fluences, con’t • Three sets of 25Mg implants are available • HRL 2002, Kroko 2006, Kroko 2007 (K7).. • SW data based on Si and Sandia using K7A internal standard implants into flight sample. • Control pieces of Si included in flight sample implants (K7A). • 2007 implant has high fluence 25Mg implant (K7C) which can be analyzed accurately by isotopic dilution. • Independent calibrations by TIMS (JPL) and ICPMS (FSU) in progress. • relative K7C and K7A fluences for other implants can be measured precisely by SIMS • Replicate measurements at ASU and CIW have been carried out • Complications with dead time in high fluence samples, transient sputtering effects presumably under control. • Precision of profilometry pit depths has been an issue, but apparently resolved (following slides)

47. Precision of sputter pit depth measurements. • SIMS solar wind fluences based on concentration depth integral. • Depth scale requires post-analysis measurement of depth of sputter pit. • Discrepancy on some of the CIW K7C implant (previous page) pit depths: • Two different instruments have been used. Interferometer (UCLA, CIT) and stylus profilometers (ASU, NIST). • Two separate intercomparisons of ASU and UCLA on other samples have given good agreement. • A subset of the CIW K7C pits show a systematic 10% difference between the interferometer and stylus profilometer depths. • Two different instruments of each kind agree with each other, but the inter-instrument difference remains! • Nevertheless, when the K7C/K7A fluence ratio calculated using only interferometer or only stylus pits, good agreement is obtained. • saved by internal consistency ! K7A/K7C fluence ratio (x10-4) CIW profiles Stylus (NIST) 3.51 Interferometer (UCLA) 3.47

48. ASU-CIW comparison of K7A/K7C relative fluence • Comparison on previous page involved only different depth scale calibrations for SIMS profiles of implants measured at CIW. • Comparison of relative fluences from ASU and CIW: K7A/K7C relative 25Mg fluence (x10-4) CIW 3.49 ± 0.07 ASU 3.06 ± 0.21 It would be nice to have better agreement than this. Part of the problem is trying to accurately measure fluences that differ by a factor of 3000. Plan: Isotopic dilution calibrations of K7C have no blank issues. Isotopic dilution measurement of K7A directly assumed to be difficult but if blanks good, may be possible to measure K7A directly. This will be assessed once isotopic dilution measurements of K7C are made.

49. Resonance Ionization Mass Spectrometry (RIMS) essentials. • RIMS analysis begins with sputtering with a primary ion beam, like SIMS. • Analyses on 100x200 micron spots. • However, only roughly 1/1000 of the atoms sputtered are the ions utilized by SIMS. • RIMS ionizes the sputtered neutral species by timing ionizing laser pulses with an ion beam pulse with mass analysis by time-of-flight mass spectrometry. • Laser duty cycle limits acquisition time, but improvements have doubled this from 1 to 2 kHz • A very large fraction (>10%) of the neutrals can be ionized and counted, producing very high sensitivity. • About 20% has been demonstrated for Mg. • The photoionization takes place in two steps. • One laser frequency is highly tuned to excite the selected atom into an excited state. This provides high selectivity of the element being analyzed from any molecular ions of the same mass. • A second laser ionizes the excited atom which is detected by the time of flight mass spectrometer. • A RIMS instrument designed specifically for Genesis samples is operating at ANL. • Optical imaging system allows particles down to micron size to be avoided. • At present, both SIMS and RIMS are useful for Genesis samples, but eventually only RIMS will be able to analyze elements of low abundance. • Present detection limit is below 50 ppt.

50. RIMS Mg Analysis (ANL; Veryovkin et al LPSC 2009 abstract) Laser schemes for simultaneous Ca and Cr analysis have been worked out. Figure shows both SW Cr and Ca depth profiles. The solar wind has a distribution of energies. The superb RIMS depth resolution is illustrated with the use of a logarithmic depth scale. Surface contamination (below about 1020 primary ions/cm2) and solar wind are only partially resolved.. The Ca fluence derived for Si (1.3 e11 atoms/cm2) is close to a very preliminary SIMS value. The RIMS Cr fluence is about x10 higher, probably due to inadequate separation of surface contmaination. An acid-cleaned sample is scheduled for analysis.