期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2015
卷号：112
期号：23
页码：7129-7134
DOI：10.1073/pnas.1502796112
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：SignificanceRefractory organics are the main hosts of carbon, nitrogen, and other biogenic elements in primitive solar system material. We have synthesized refractory organics by ionizing a gas mixture reminiscent of the composition of the protosolar nebula, at temperatures up to 1,000 K in a plasma. Synthesized compounds share chemical and structural features with chondritic organics, and trapped noble gases reproduce well the elemental and isotopic characteristics of meteoritic noble gases. Our study suggests that organosynthesis took place in the solar system, including in its warm regions, and was ubiquitous anywhere the nebular gas was subject to ionization. In the nascent solar system, primitive organic matter was a major contributor of volatile elements to planetary bodies, and could have played a key role in the development of the biosphere. However, the origin of primitive organics is poorly understood. Most scenarios advocate cold synthesis in the interstellar medium or in the outer solar system. Here, we report the synthesis of solid organics under ionizing conditions in a plasma setup from gas mixtures (H2(O)-CO-N2-noble gases) reminiscent of the protosolar nebula composition. Ionization of the gas phase was achieved at temperatures up to 1,000 K. Synthesized solid compounds share chemical and structural features with chondritic organics, and noble gases trapped during the experiments reproduce the elemental and isotopic fractionations observed in primitive organics. These results strongly suggest that both the formation of chondritic refractory organics and the trapping of noble gases took place simultaneously in the ionized areas of the protoplanetary disk, via photon- and/or electron-driven reactions and processing. Thus, synthesis of primitive organics might not have required a cold environment and could have occurred anywhere the disk is ionized, including in its warm regions. This scenario also supports N2 photodissociation as the cause of the large nitrogen isotopic range in the solar system.
