09:30 〜 09:45
[PPS07-03] Sugars in Antarctic CM chondrites
キーワード：CM2コンドライト、糖、水質変質、GC-MS
Carbonaceous chondrites contain various organic compounds, including all three biologically essential molecules: amino acids, nucleobases, and sugars. Abundances and compositions of amino acids and nucleobases have been investigated for many chondrites. These analyses allowed us to discuss the effects of parent body processing, source materials, and formation mechanisms. However, biologically important sugars have only been reported in two meteorites. Ribose, the sole RNA sugar, was found in the Murchison meteorite (CM 2.5) and NWA 801 meteorite (CR 3.0–2.8) along with its isomers (lyxose, arabinose, and xylose). These meteorites have different chemical groups and petrologic types, and thus, their effects are unclear. CM chondrites are one of the most abundant groups of carbonaceous chondrites with a high organics content. We investigated compositions and abundances of sugars in three Antarctic CM chondrites of different petrologic types: Asuka 12236 (CM 2.9), Lonewolf Nunataks (LON) 94101 (CM 2.2–2.3), and Meteorite Hills (MET) 01070 (CM 2.0) through gas chromatography/mass spectrometry (GC-MS).
Ribose and arabinose, two of the four aldopentoses, were detected in the Asuka 12236 at 9.4 ppb in total. All four aldopentoses (ribose, lyxose, arabinose, xylose) were identified in LON 94101 with total concentrations of 71 ppb. These sugars were below the detection limit in MET 01070. Aldohexoses (mannose, glucose, galactose) were identified in Asuka 12236 and LON 94101 with higher abundances than aldopentoses. Deoxyribose and tetroses were below the detection limit in all of the samples.
The finding of aldopentoses and aldohexoses in Antarctic chondrites that experienced minimal terrestrial contamination further supports the delivery of bio-important sugars from space. The abundance of aldopentoses in the most primitive Asuka 12236 was lower than that in the Murchison CM 2.5 (331.7 ppb) and LON 94101 CM 2.2–2.3 (71 ppb). This indicates that the abundance of sugars increased in incipient aqueous processing and decreased in a significant alteration in CM parent body asteroids. This further suggests that asteroidal processing was responsible for forming sugars supplied to the Earth as most CM chondrites experienced certain levels of asteroidal aqueous processing.
Ribose and arabinose, two of the four aldopentoses, were detected in the Asuka 12236 at 9.4 ppb in total. All four aldopentoses (ribose, lyxose, arabinose, xylose) were identified in LON 94101 with total concentrations of 71 ppb. These sugars were below the detection limit in MET 01070. Aldohexoses (mannose, glucose, galactose) were identified in Asuka 12236 and LON 94101 with higher abundances than aldopentoses. Deoxyribose and tetroses were below the detection limit in all of the samples.
The finding of aldopentoses and aldohexoses in Antarctic chondrites that experienced minimal terrestrial contamination further supports the delivery of bio-important sugars from space. The abundance of aldopentoses in the most primitive Asuka 12236 was lower than that in the Murchison CM 2.5 (331.7 ppb) and LON 94101 CM 2.2–2.3 (71 ppb). This indicates that the abundance of sugars increased in incipient aqueous processing and decreased in a significant alteration in CM parent body asteroids. This further suggests that asteroidal processing was responsible for forming sugars supplied to the Earth as most CM chondrites experienced certain levels of asteroidal aqueous processing.