Overview of the rocky component of Wild 2 comet samples: Insight into the early solar system, relationship with meteoritic materials and the differences between comets and asteroids
Overview of the rocky component of Wild 2 comet samples: Insight into the early solar system, relationship with meteoritic materials and the differences between comets and asteroids
复制标题
DOI：
10.1111/j.1945-5100.2012.01339.x
复制
发表时间：
2012-04-01
影响因子：
2.2
通讯作者：
Matrajt, Graciela
中科院分区：
文献类型：
--
作者：
Brownlee, Don;Joswiak, Dave;Matrajt, Graciela
怀尔德2号彗星210亩的固体样本提供了一个有限但直接的太阳星云固体的视图，这些固体是通过吸积形成木星家族彗星的。星尘号收集的样本主要由高温材料组成，与陨石成分非常相似。这些物质包括球粒和cai样碎片。已经发现了五个前太阳系颗粒，但很明显，同位素异常的前太阳系颗粒只是彗星的一小部分。虽然不确定，但太阳系前的颗粒含量可能比球粒陨石和大多数行星际尘埃颗粒中发现的要高。经分析的怀尔德2号彗星的大部分固体似乎都是在高温的岩石形成环境中产生的，然后它们被运送到海王星的轨道上，在那里它们与冰和有机成分一起聚集，形成了怀尔德2号彗星。我们假设Wild 2的岩石成分是由包括行星和陨石母体在内的所有天体吸积的无处不在的星云固体流的样本。小行星和彗星岩石成分的主要区别在于，彗星主要由这种广泛分布的成分组成。小行星含有这种成分，但主要是由当地制造的物质组成，这些物质赋予球粒陨石群独特的性质。由于这种情况下的大量径向混合，似乎大多数彗星都含有类似的岩石物质混合。如果这一假设是正确的，那么橄榄石中的氧同位素和微量元素丰度等特性应该比任何球粒陨石群的弥散范围更广，这可能是由广泛运输的成分组成的原始太阳系外天体的特征。
The solid 210 mu m samples of comet Wild 2 provide a limited but direct view of the solar nebula solids that accreted to form Jupiter family comets. The samples collected by the Stardust mission are dominated by high-temperature materials that are closely analogous to meteoritic components. These materials include chondrule and CAI-like fragments. Five presolar grains have been discovered, but it is clear that isotopically anomalous presolar grains are only a minor fraction of the comet. Although uncertain, the presolar grain content is perhaps higher than found in chondrites and most interplanetary dust particles. It appears that the majority of the analyzed Wild 2 solids were produced in high-temperature rock forming environments, and they were then transported past the orbit of Neptune, where they accreted along with ice and organic components to form comet Wild 2. We hypothesize that Wild 2 rocky components are a sample of a ubiquitously distributed flow of nebular solids that was accreted by all bodies including planets and meteorite parent bodies. A primary difference between asteroids and the rocky content of comets is that comets are dominated by this widely distributed component. Asteroids contain this component, but are dominated by locally made materials that give chondrite groups their distinctive properties. Because of the large radial mixing in this scenario, it seems likely that most comets contain a similar mix of rocky materials. If this hypothesis is correct, then properties such as oxygen isotopes and minor element abundances in olivine, should have a wider dispersion than in any chondrite group, and this may be a characteristic property of primitive outer solar system bodies made from widely transported components.