[论文解读] Assessments of the energy, mass and size of the Chicxulub Impactor

H. J. Durand-Manterola, G. Cordero|arXiv (Cornell University)|Mar 19, 2014

Astro and Planetary Science参考文献 9被引用 3

一句话总结

本研究利用K/Pg界线层中的铱丰度和陨石数据，估算希克苏鲁伯撞击体的动能、质量与直径。结果表明，撞击体最可能为彗星，其动能介于1.3×10²⁴ J至5.8×10²⁵ J之间，质量为1.0×10¹⁵ kg至4.6×10¹⁷ kg，直径范围为10.6 km至80.9 km。

ABSTRACT

In 1980, Alvarez and colleagues proposed that, in the transition from the Cretaceous to Paleogene, a large impactor collided with Earth being the cause of the mass extinction occurred at the limit K / Pg. In 1980 there was no known impact structure, which could be responsible for this extinction. It was not until 1991 that an international group of researchers proposed that a circular structure between 180 and 200 km, buried under Tertiary deposits in the Yucatan Peninsula in Mexico, was the crater formed by the impact proposed by the group of Alvarez (Hildebrand et al., 1991). It is very probable that an impact of this magnitude have had large effects on the surface and in the environment. To study these effects, it is necessary to estimate the characteristics that the impactor had. The literature often mentions the nature of the impactor, and has been proposed both an asteroid and a comet, and even a comet shower that produced periodic extinctions. However, the physical parameters of the impactor are not limited, so the aim of this study is to estimate the most relevant features of this one such as the size, mass and kinetic energy. We found that the kinetic energy of the impactor is in the range from 1.3e24 J to 5.8e25 J. The mass is in the range of 1.0e15 kg to 4.6e17 kg. Finally, the diameter of the object is in the range of 10.6 km to 80.9 km. Based on the mass of the impactor and iridium abundance in different types of meteorites, we calculate the concentration of iridium, which should be observed in the K/Pg layer. When compared with the measurements, we concluded that the best estimation is that the impactor was a comet.

研究动机与目标

• 估算导致K/Pg灭绝事件的希克苏鲁伯撞击体的物理参数——质量、直径与动能。
• 通过将预测的铱浓度与K/Pg层中实测值进行比较，解决撞击体是小行星还是彗星的长期争议。
• 基于地质证据推导的能量与质量约束，提供撞击体特征的物理解释一致的范围。
• 通过整合陨石成分数据与撞击能量计算，改进现有希克苏鲁伯撞击体模型。

提出的方法

• 利用公式E = ½mv²计算撞击体的动能，其中质量与速度由撞击坑尺寸及能量标度定律推导得出。
• 通过能量约束结合已知的希克苏鲁伯撞击坑直径（180–200 km）及撞击能量标度关系，估算质量范围。
• 利用碳质球粒陨石中铱丰度及K/Pg界线层中的铱含量，反推出撞击体中预期的铱浓度。
• 将撞击体中预测的铱含量与K/Pg层中实测的铱水平进行比较，以评估小行星或彗星起源的可能性。
• 应用统计与物理建模，约束与观测到的撞击坑及地球化学数据一致的尺寸、质量与能量范围。
• 评估不同撞击体成分与观测到的地球化学特征的一致性，基于铱产量结果更倾向于彗星起源。

实验结果

研究问题

• RQ1 基于撞击坑尺寸与撞击动力学，形成希克苏鲁伯撞击坑所需的动能范围是什么？
• RQ2 与观测到的撞击能量及撞击坑尺寸一致的质量与直径范围是什么？
• RQ3 基于陨石数据预测的撞击体中铱浓度与K/Pg界线层中实测值相比如何？
• RQ4 基于铱丰度与地球化学约束，撞击体更可能为小行星还是彗星？
• RQ5 哪些物理参数（质量、尺寸、能量）最能调和K/Pg撞击事件的地质与地球化学证据？

主要发现

• 基于撞击坑尺寸与能量标度模型，希克苏鲁伯撞击体的动能范围为1.3×10²⁴ J至5.8×10²⁵ J。
• 撞击体质量估算范围为1.0×10¹⁵ kg至4.6×10¹⁷ kg，取决于假设的成分与速度。
• 撞击体直径范围为10.6 km至80.9 km，上限受太阳系天体可能最大尺寸的限制。
• 基于陨石数据预测的撞击体中铱浓度，与K/Pg层中实测的铱水平高度吻合。
• 预测与观测到的铱水平之间的一致性支持撞击体最可能为彗星而非小行星的结论。
• 本研究结论认为，彗星起源最能解释希克苏鲁伯撞击事件的地球化学与能量约束。