Dark primitive asteroids account for a large share of K/Pg-scale impacts on the Earth
Dark primitive asteroids account for a large share of K/Pg-scale impacts on the Earth
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DOI：
10.1016/j.icarus.2021.114621
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发表时间：
2021-07-17
期刊：
影响因子：
3.2
通讯作者：
Marchi, Simone
中科院分区：
文献类型：
--
作者：
Nesvorny, David;Bottke, William F.;Marchi, Simone
本文建立了一个大型近地小行星（NEAs）的动力学模型，以了解K/Pg尺度撞击地球的发生率和性质。我们发现，在1 Gyr内，预计将有16-32（2-4）个直径D > 5公里（D > 10公里）的近地小行星撞击地球，其中大约一半的撞击物是黑暗的原始小行星（其中大多数的半长轴D > 2.5 Au）。这些结果解释了为什么希克苏鲁布陨石坑，地球上发现的第三大撞击结构（直径。180公里），是由碳质球粒陨石的影响。这些结果表明，在结合以前公布的小型（D小于或接近1公里）近地小行星的结果时，可以对主带进行取决于大小的取样。我们的结论是，触发类似或等于6600万年前的K/Pg大灭绝的撞击物是一个主带小行星，很可能（类似或等于60%的概率）起源于2.5 Au以上。
A dynamical model for large near-Earth asteroids (NEAs) is developed here to understand the occurrence rate and nature of Cretaceous-Paleogene (K/Pg) scale impacts on the Earth. We find that 16-32 (2-4) impacts of diameter D > 5 km (D > 10 km) NEAs are expected on the Earth in 1 Gyr, with about a half of impactors being dark primitive asteroids (most of which start with semimajor axis D > 2.5 au). These results explain why the Chicxulub crater, the third largest impact structure found on the Earth (diameter. 180 km), was produced by impact of a carbonaceous chondrite. They suggest, when combined with previously published results for small (D less than or similar to 1 km) NEAs, a size-dependent sampling of the main belt. We conclude that the impactor that triggered the K/Pg mass extinction similar or equal to 66 Myr ago was a main belt asteroid that quite likely (similar or equal to 60% probability) originated beyond 2.5 au.