Abstract
Three category 3 (organic) particles (RB-QD04-0001, RB-QD04-0047-02, and RA-QD02-0120) and so-called ‘white object’ found in the sample container have been examined by micro-Raman and infrared (IR) spectroscopy. In addition, several artificial substances that could occur as possible contaminants and chondritic insoluble organic matter (IOM) prepared from the Murchison CM2 chondrite were analyzed. The Raman spectra of the particles show broad G-band and weak D-band. The G-band parameters plot in the disordered region and close to the artifact produced from a Viton glove after laser exposure rather than chondritic IOM. The particles were therefore originally at low maturity level, suggesting that they have not experienced strong heating and are therefore not related to the LL4-6 parent body. The IR spectra are not similar to that of chondritic IOM. Furthermore, the particles cannot be identified as some artificial carbonaceous substances, including the white object, which are the possible contaminants, examined in this investigation. Although it cannot be determined exactly whether the three category 3 particles are extraterrestrial, the limited IR and Raman results in this investigation strongly suggest their terrestrial origin. Although they could not be directly related to the artificial contaminants examined in this investigation, they may yet be reaction products from similar substances that flew on the mission. In particular, RB-QD04-0047-02 shows several infrared spectral absorption bands in common with the ‘white object.’ This may relate to the degradation of a polyimide/polyamide resin.
Highlights
The Hayabusa space craft returned to the Earth on 13 June 2010 from the Muses-C region on the asteroid Itokawa with more than 1,500 tiny particles (e.g., Nakamura et al 2011)
Particles belonging to categories 1 and 2 have been confirmed as Itokawa regolith (e.g., Ebihara et al 2011; Nagao et al 2011; Nakamura et al 2011; Noguchi et al 2011; Tsuchiyama et al 2011; Yurimoto et al 2011)
As a part of the sequential analysis of category 3 particles, we examined three category 3 particles (RB-QD04-0001, RBQD04-0047-02, and RA-QD02-0120) by micro-Raman and Fourier transform infrared (FTIR) spectroscopies, together with several artificial carbonaceous substances including the ‘white object’ found in the sample container
Summary
The Hayabusa space craft returned to the Earth on 13 June 2010 from the Muses-C region on the asteroid Itokawa with more than 1,500 tiny particles (e.g., Nakamura et al 2011). More than 450 particles have been picked up from the sample catcher (Uesugi et al 2014). The recovered particles have been classified into four categories (Yada et al 2014). Category 4 particles are artificial materials such as aluminum flakes (Yada et al 2014), and the so-called ‘white object’ found in the sample container (http://hayabusaao.isas.jaxa.jp/catalog/contaminations.pdf ) may be included in this category. Particles belonging to categories 1 and 2 have been confirmed as Itokawa regolith (e.g., Ebihara et al 2011; Nagao et al 2011; Nakamura et al 2011; Noguchi et al 2011; Tsuchiyama et al 2011; Yurimoto et al 2011)
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