Migration of D-type asteroids from the outer Solar System inferred from carbonate in meteorites
Migration of D-type asteroids from the outer Solar System inferred from carbonate in meteorites
复制标题
DOI：
10.1038/s41550-019-0801-4
复制
发表时间：
2019-10-01
期刊：
影响因子：
14.1
通讯作者：
Sano, Y.
中科院分区：
文献类型：
--
作者：
Fujiya, W.;Hoppe, P.;Sano, Y.
最近的太阳系演化动力学模型和陨石中岩石形成元素的同位素研究表明，富含挥发物的小行星形成于木星轨道以外的外太阳系，尽管它们目前位于主小行星带（1-4）。小行星形成时的环境温度是确定小行星原始位置的一个关键诊断因素，可能由它们所含挥发物的丰度决定。特别是，陨石中碳酸盐的丰度和C-13/C-12比率记录了其母小行星中含碳挥发性物质的丰度。然而，这些碳酸盐的碳源仍然知之甚少（5-8）。在这里，我们表明，塔吉什湖陨石含有丰富的碳酸盐与一贯高C-13/C-12的比例。塔吉什湖富含C-13的碳酸盐的高丰度排除了有机物作为其主要碳源（5，9）。因此，塔吉什湖的母体，可能是一颗D型小行星（10），一定是吸积了大量富含C-13的CO2冰。塔吉什湖冰的C-13/C-12和CO2/H2O比值估计值与彗星冰相似（11，12）。因此，我们推断至少有一些D-型小行星形成于寒冷的外太阳系，随后由于巨行星的轨道不稳定性而被运送到内太阳系（1，3）。
Recent dynamical models of Solar System evolution and isotope studies of rock-forming elements in meteorites have suggested that volatile-rich asteroids formed in the outer Solar System beyond Jupiter's orbit, despite being currently located in the main asteroid belt(1-4). The ambient temperature under which asteroids formed is a crucial diagnostic to pinpoint the original location of asteroids and is potentially determined by the abundance of volatiles they contain. In particular, abundances and C-13/C-12 ratios of carbonates in meteorites record the abundances of carbon-bearing volatile species in their parent asteroids. However, the sources of carbon for these carbonates remain poorly understood(5-8). Here we show that the Tagish Lake meteorite contains abundant carbonates with consistently high C-13/C-12 ratios. The high abundance of C-13-rich carbonates in Tagish Lake excludes organic matter as their main carbon source(5,9). Therefore, the Tagish Lake parent body, presumably a D-type asteroid(10), must have accreted a large amount of C-13-rich CO2 ice. The estimated C-13/C-12 and CO2/H2O ratios of ice in Tagish Lake are similar to those of cometary ice(11,12). Thus, we infer that at least some D-type asteroids formed in the cold outer Solar System and were subsequently transported into the inner Solar System owing to an orbital instability of the giant planets(1,3).