5:15 PM - 6:45 PM
[PPS08-P18] In situ analysis of soluble organic matter for Hayabusa category 3 particles
Keywords:Hayabusa category 3 patricles, Soluble organic matter, In situ analysis
[Introduction] The carbonaceous materials recovered from the sample catcher of Hayabusa spacecraft were assigned as category 3 particles by the ESCuC/JAXA [1]. The carbonaceous particles associated with silicate particles were investigated during the initial analysis, however, no evidence of their extraterrestrial origin was found [2]. The category 3 particles were investigated by Hayabusa Sample Preliminary Examination Team dedicated to the category 3 particles (HASPET-C3) using several techniques, such as NanoSIMS, STXM-XANES, micro-Raman, and TOF-SIMS [3-6], furthermore, in situ coordinated microanalysis were also conducted [7]. So far, contaminations before/after the operation of the Hayabusa spacecraft were suggested as possible origins but still in debate. In this study, we conducted in situ analyses of soluble organic matter (SOM) on category 3 particles using the desorption electrospray ionization (DESI) technique coupled with high-mass-resolution mass spectrometry (HRMS) [8] to further characterization of the category 3 particles and investigate their origin.
[Samples and Analytical Methods] Two category 3 carbonaceous particles (RB-CV-0008 and RB-CV-0031) with 56 µm and 61 µm, respectively, were analyzed in this study. Each particle was mounted onto a gold plate (t = 0.3 mm) fixed with an Al-stub holder by pressing with sapphire glass for DESI-HRMS analysis. DESI–HRMS imaging was performed using a 2D DESI ion source (Omni Spray Source 2D, Prosolia Inc.) equipped with a Orbitrap mass spectrometer (Q-Exactive Plus, Thermo Fisher Scientific). Methanol 100% of LC–MS grade was used as the spray solvent with flow rate of 2.5 µL/min. After DESI-HRMS imaging, the samples were investigated by SEM-EDS. We also analyzed a piece of VECTRAN and VITON from fluoro rubber gloves, and several commercial polymer samples, such as acryl, poly carbonate, polyethyl benzene-1,4-dicarboxylate (PET), and Nylon-6 for comparison.
[Results and Discussion] Total 178 positive ions were successfully identified from the surface of RB-CV-0008 among m/z 70–1000. RB-CV-0031 was unfortunately lost during the analysis. The chemical compositions of these ions were assigned using their exact mass, and CHNO, and CHO compounds were abundant in both number and total ion intensity. Several different families containing units of ±(C3H6O)n (m/z 58.0418) were identified among these ions. The results of DESI–HRMS imaging and EDS spectral features of RB-CV-0008 were similar to those of Nylon-6. The presence of homologues with units of m/z 58.0418 ±(C3H6O)n in the positive ion detected by DESI–HRMS imaging suggested that RB-CV-0008 had a structure similar to that of polyethylene glycol (PPG). Based on these results, RB-CV-0008 is most likely a carbonaceous particle corresponding to polyamide, a degradation product of polyimide resin from the sample container of the Hayabusa spacecraft, or a mixture of PPG and polyamide derived from plasticizers. Our results are consistent with previous analytical results for Category 3 particles [e.g., 7] and suggest that the RB-CV-0008 particles are terrestrial materials from the sample chamber or laboratory.
[References] [1] Yada et al. (2014) Meteorit. Planet. Sci. 49, 135. [2] Naraoka et al. (2012) Geochem J. 46, 61. [3] Ito et al. (2014) Earth Planets Space. 66, 91. [4] Uesugi et al., (2014) Earth Planets Space. 66, 102. [5] Yabuta et al. (2014) Earth Planets Space. 66, 156. [6] Kitajima et al. (2015) Earth Planets Space. 67, 20. [6] Naraoka et al. (2015) Earth Planets Space. 67, 67. [7] Uesugi et al. (2019) Meteorit. Planet. Sci.54, 638. [8] Hashiguchi and Naraoka (2019) Meteorit. Planet. Sci. 54, 452.
[Samples and Analytical Methods] Two category 3 carbonaceous particles (RB-CV-0008 and RB-CV-0031) with 56 µm and 61 µm, respectively, were analyzed in this study. Each particle was mounted onto a gold plate (t = 0.3 mm) fixed with an Al-stub holder by pressing with sapphire glass for DESI-HRMS analysis. DESI–HRMS imaging was performed using a 2D DESI ion source (Omni Spray Source 2D, Prosolia Inc.) equipped with a Orbitrap mass spectrometer (Q-Exactive Plus, Thermo Fisher Scientific). Methanol 100% of LC–MS grade was used as the spray solvent with flow rate of 2.5 µL/min. After DESI-HRMS imaging, the samples were investigated by SEM-EDS. We also analyzed a piece of VECTRAN and VITON from fluoro rubber gloves, and several commercial polymer samples, such as acryl, poly carbonate, polyethyl benzene-1,4-dicarboxylate (PET), and Nylon-6 for comparison.
[Results and Discussion] Total 178 positive ions were successfully identified from the surface of RB-CV-0008 among m/z 70–1000. RB-CV-0031 was unfortunately lost during the analysis. The chemical compositions of these ions were assigned using their exact mass, and CHNO, and CHO compounds were abundant in both number and total ion intensity. Several different families containing units of ±(C3H6O)n (m/z 58.0418) were identified among these ions. The results of DESI–HRMS imaging and EDS spectral features of RB-CV-0008 were similar to those of Nylon-6. The presence of homologues with units of m/z 58.0418 ±(C3H6O)n in the positive ion detected by DESI–HRMS imaging suggested that RB-CV-0008 had a structure similar to that of polyethylene glycol (PPG). Based on these results, RB-CV-0008 is most likely a carbonaceous particle corresponding to polyamide, a degradation product of polyimide resin from the sample container of the Hayabusa spacecraft, or a mixture of PPG and polyamide derived from plasticizers. Our results are consistent with previous analytical results for Category 3 particles [e.g., 7] and suggest that the RB-CV-0008 particles are terrestrial materials from the sample chamber or laboratory.
[References] [1] Yada et al. (2014) Meteorit. Planet. Sci. 49, 135. [2] Naraoka et al. (2012) Geochem J. 46, 61. [3] Ito et al. (2014) Earth Planets Space. 66, 91. [4] Uesugi et al., (2014) Earth Planets Space. 66, 102. [5] Yabuta et al. (2014) Earth Planets Space. 66, 156. [6] Kitajima et al. (2015) Earth Planets Space. 67, 20. [6] Naraoka et al. (2015) Earth Planets Space. 67, 67. [7] Uesugi et al. (2019) Meteorit. Planet. Sci.54, 638. [8] Hashiguchi and Naraoka (2019) Meteorit. Planet. Sci. 54, 452.