10:45 〜 12:15
[MIS03-P04] 隕石母天体での水熱過程によるホルモース型単糖類生成におけるアンモニアとカンラン石の影響
キーワード：隕石母天体、単糖類、水熱過程
1. Introduction
Monosaccharides and their derivatives are used in various parts of living organisms, and they are important as building blocks of life.
One of the possible environments for prebiotic formation of monosaccharides, we focus on the theory that monosaccharides were synthesized in meteorite parent bodies and then brought to the earth. The parent bodies of carbonaceous chondrites may have contained starting materials for sugar synthesis. Monosaccharides could have synthesized by various reactions during aqueous alteration, including formose-type reaction[1].
In this study, we assumed the simplest hydrothermal system of water, ammonia, formaldehyde, and methanol (hereafter referred to as the FAMW), using the heat generated by the radioactive decay of 26Al in the meteorite parent body. We conducted laboratory experiments to evaluate monosaccharide formation in the meteorite parent body during aqueous alteration and its dependances of the composition of the starting solutions, the heating temperatures, and the heating durations.
2. Methods
We conducted three sets of experiments. In Experiment 1, the heating temperature was fixed at 150 ℃, and the FAMW solutions with several different ratios of formaldehyde and ammonia were prepared, in order to examine the effects of compositional differences. The heating temperature 150 ℃ was selected based on the maximum temperature in the CI and CM carbonaceous chondrite parent bodies[2].
In Experiment 2, the composition ratios of the starting solutions were fixed based on the results of Experiment 1, and experiments were conducted at 50 ℃ and 150 ℃ in order to evaluate the effects of temperatures to the formation of monosaccharides.
In Experiment 3, in order to investigate the possibility that minerals in the meteorite parent body may have played a catalytic role in the formation of monosaccharides, olivine was mixed into the starting solutions, and experiments were conducted at 50 ℃ and 150 ℃.
3. Results
Experiment 1 suggested that the presence of large amounts of ammonia, which is necessary as a base catalyst for the formose reaction, may inhibit monosaccharide formation.
From Experiment 2, it was found that the amount of monosaccharides formed at 50 ℃ was negligible compared to that at 150 ℃ and that the amount of monosaccharides measured at both temperatures tended to increase and then decrease a short time after the start of heating.
From Experiment 3, it was observed that when olivine was added to the starting solutions, the amount of monosaccharides produced tended to increase at 150 ℃.
4. Discussion
In this study, a certain amount of monosaccharides were produced at 150 ℃ heating. This is the maximum temperature in the CI and CM chondrite parent bodies, indicating that monosaccharide production is possible in the meteorite parent body. On the other hand, more than four-carbon monosaccharides didn’t produce at 50 ℃ heating, suggesting that there may be a threshold temperature between these temperatures. The increase or decrease in the amount of monosaccharide production with the change in heating time is assumed to be a result of competition between monosaccharide production by the formose reaction and monosaccharide consumption by the reaction of monosaccharides with each other or with other substances. The results of Experiment 3 suggest that olivine may have promoted monosaccharide formation. Further investigation is needed, such as microscopic observation of the olivine surface after heating experiments.
It is necessary to investigate the temperatures of monosaccharide formation in more detail, considering the differences in the maximum temperatures of various chondrite parent bodies and the possibility that gamma rays generated during 26Al radioactive decay may have been involved in the reaction[3].
5. References
[1] G. D. Cody et al., PNAS, 108, 19171-19176, 2011
[2] A. J. Brearley, in Meteorites and the Early Solar System II, 587-624, 2006
[3] S. Abe et al., in this meeting
Monosaccharides and their derivatives are used in various parts of living organisms, and they are important as building blocks of life.
One of the possible environments for prebiotic formation of monosaccharides, we focus on the theory that monosaccharides were synthesized in meteorite parent bodies and then brought to the earth. The parent bodies of carbonaceous chondrites may have contained starting materials for sugar synthesis. Monosaccharides could have synthesized by various reactions during aqueous alteration, including formose-type reaction[1].
In this study, we assumed the simplest hydrothermal system of water, ammonia, formaldehyde, and methanol (hereafter referred to as the FAMW), using the heat generated by the radioactive decay of 26Al in the meteorite parent body. We conducted laboratory experiments to evaluate monosaccharide formation in the meteorite parent body during aqueous alteration and its dependances of the composition of the starting solutions, the heating temperatures, and the heating durations.
2. Methods
We conducted three sets of experiments. In Experiment 1, the heating temperature was fixed at 150 ℃, and the FAMW solutions with several different ratios of formaldehyde and ammonia were prepared, in order to examine the effects of compositional differences. The heating temperature 150 ℃ was selected based on the maximum temperature in the CI and CM carbonaceous chondrite parent bodies[2].
In Experiment 2, the composition ratios of the starting solutions were fixed based on the results of Experiment 1, and experiments were conducted at 50 ℃ and 150 ℃ in order to evaluate the effects of temperatures to the formation of monosaccharides.
In Experiment 3, in order to investigate the possibility that minerals in the meteorite parent body may have played a catalytic role in the formation of monosaccharides, olivine was mixed into the starting solutions, and experiments were conducted at 50 ℃ and 150 ℃.
3. Results
Experiment 1 suggested that the presence of large amounts of ammonia, which is necessary as a base catalyst for the formose reaction, may inhibit monosaccharide formation.
From Experiment 2, it was found that the amount of monosaccharides formed at 50 ℃ was negligible compared to that at 150 ℃ and that the amount of monosaccharides measured at both temperatures tended to increase and then decrease a short time after the start of heating.
From Experiment 3, it was observed that when olivine was added to the starting solutions, the amount of monosaccharides produced tended to increase at 150 ℃.
4. Discussion
In this study, a certain amount of monosaccharides were produced at 150 ℃ heating. This is the maximum temperature in the CI and CM chondrite parent bodies, indicating that monosaccharide production is possible in the meteorite parent body. On the other hand, more than four-carbon monosaccharides didn’t produce at 50 ℃ heating, suggesting that there may be a threshold temperature between these temperatures. The increase or decrease in the amount of monosaccharide production with the change in heating time is assumed to be a result of competition between monosaccharide production by the formose reaction and monosaccharide consumption by the reaction of monosaccharides with each other or with other substances. The results of Experiment 3 suggest that olivine may have promoted monosaccharide formation. Further investigation is needed, such as microscopic observation of the olivine surface after heating experiments.
It is necessary to investigate the temperatures of monosaccharide formation in more detail, considering the differences in the maximum temperatures of various chondrite parent bodies and the possibility that gamma rays generated during 26Al radioactive decay may have been involved in the reaction[3].
5. References
[1] G. D. Cody et al., PNAS, 108, 19171-19176, 2011
[2] A. J. Brearley, in Meteorites and the Early Solar System II, 587-624, 2006
[3] S. Abe et al., in this meeting