CAB：走向星际介质中的RNA世界--尿素的探测，2-氨基恶唑和单糖的研究
CAB: Towards the RNA-world in the interstellar medium -- detection of urea, and search of 2-amino-oxazole and simple sugars
摘要：
在过去的十年中，天体化学已经见证了复杂有机分子探测数量的惊人增长。其中一些物种是益生元的兴趣，如乙醇醛，最简单的糖，或氨基乙腈，甘氨酸的可能前体。最近，我们已经报道了两个新的含氮复杂的有机物，乙醇腈和Z-氰基甲亚胺，已知的是在形成过程中的核糖核苷酸的原始核糖核酸（RNA）的理论-世界的生命起源的中间物种的检测。在本文中，我们提出了深入和高灵敏度的观测对两个最丰富的化学源在银河系：一个巨大的分子云在银河系中心（G+0.693-0.027）和原太阳（IRAS 16293 -2422 B）。我们的目标是探索被认为是驱动原始RNA世界化学的关键前体是否也在太空中发现。我们的高灵敏度观测结果表明，尿素存在于G+0.693-0.027中，丰度约为5x 10 -11。这是第一次在恒星形成区域之外发现这种前生命物种。尿素在原太阳IRAS 16293 -2422 B附近仍然未被检测到（其丰度上限小于2x 10 -11）。RNA世界化学方案的其他前体，如乙醇醛或氰胺，在太空中很丰富，但关键的益生元物种，如2-氨基恶唑，甘油醛或二羟基丙酮，在这两种来源中都没有检测到。未来将需要针对这些物种的最亮过渡进行更灵敏的观测，以解开这些大型前生物有机物是否确实存在于太空中。
英文摘要：
In the past decade, Astrochemistry has witnessed an impressive increase in the number of detections of complex organic molecules. Some of these species are of prebiotic interest such as glycolaldehyde, the simplest sugar, or amino acetonitrile, a possible precursor of glycine. Recently, we have reported the detection of two new nitrogen-bearing complex organics, glycolonitrile and Z-cyanomethanimine, known to be intermediate species in the formation process of ribonucleotides within theories of a primordial ribonucleic acid (RNA)-world for the origin of life. In this paper, we present deep and high-sensitivity observations toward two of the most chemically rich sources in the Galaxy: a Giant Molecular Cloud in the center of the Milky Way (G+0.693-0.027) and a proto-Sun (IRAS16293-2422 B). Our aim is to explore whether the key precursors considered to drive the primordial RNA-world chemistry, are also found in space. Our high-sensitivity observations reveal that urea is present in G+0.693-0.027 with an abundance of about 5x10-11. This is the first detection of this prebiotic species outside a star-forming region. Urea remains undetected toward the proto-Sun IRAS16293-2422 B (upper limit to its abundance of less than 2x10-11). Other precursors of the RNA-world chemical scheme such as glycolaldehyde or cyanamide are abundant in space, but key prebiotic species such as 2- amino-oxazole, glyceraldehyde or dihydroxyacetone are not detected in either source. Future more sensitive observations targeting the brightest transitions of these species will be needed to disentangle whether these large prebiotic organics are certainly present in space.
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