[Paper Review] 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 Science9 references3 citations

TL;DR

This study estimates the kinetic energy, mass, and diameter of the Chicxulub impactor using iridium abundance in the K/Pg boundary layer and meteorite data. It concludes the impactor was most likely a comet, with kinetic energy between 1.3×10²⁴ J and 5.8×10²⁵ J, mass from 1.0×10¹⁵ kg to 4.6×10¹⁷ kg, and diameter ranging from 10.6 km to 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.

Motivation & Objective

• To estimate the physical parameters—mass, diameter, and kinetic energy—of the Chicxulub impactor responsible for the K/Pg extinction.
• To resolve the ongoing debate on whether the impactor was an asteroid or a comet by comparing predicted iridium concentrations with measured values in the K/Pg layer.
• To provide a physically consistent range of impactor characteristics based on energy and mass constraints derived from geological evidence.
• To refine existing models of the Chicxulub impactor by integrating data from meteorite compositions and impact energy calculations.

Proposed method

• Calculated kinetic energy of the impactor using the formula E = ½mv², with mass and velocity derived from impact crater size and energy scaling laws.
• Estimated mass ranges by applying energy constraints to the known diameter of the Chicxulub crater (180–200 km) and impact energy scaling relationships.
• Used iridium abundance in carbonaceous chondrites and the K/Pg boundary layer to back-calculate expected iridium concentration in the impactor.
• Compared predicted iridium content in the impactor with measured iridium levels in the K/Pg layer to assess the likelihood of asteroid vs. comet origin.
• Applied statistical and physical modeling to constrain the size, mass, and energy ranges consistent with the observed crater and geochemical data.
• Evaluated the consistency of different impactor compositions with observed geochemical signatures, favoring a cometary origin based on iridium yield.

Experimental results

Research questions

• RQ1 What is the range of kinetic energy required to form the Chicxulub crater based on its size and impact dynamics?
• RQ2 What mass and diameter ranges are consistent with the observed energy and crater dimensions of the Chicxulub impactor?
• RQ3 How does the predicted iridium concentration in the impactor compare with measured values in the K/Pg boundary layer?
• RQ4 Is the impactor more likely to be an asteroid or a comet, based on iridium abundance and geochemical constraints?
• RQ5 What physical parameters (mass, size, energy) best reconcile the geological and geochemical evidence for the K/Pg impact?

Key findings

• The kinetic energy of the Chicxulub impactor ranges from 1.3×10²⁴ J to 5.8×10²⁵ J, based on crater size and energy scaling models.
• The mass of the impactor is estimated between 1.0×10¹⁵ kg and 4.6×10¹⁷ kg, depending on assumed composition and velocity.
• The diameter of the impactor ranges from 10.6 km to 80.9 km, with the upper limit constrained by the maximum plausible size for a solar system body.
• The predicted iridium concentration in the impactor, based on meteorite data, closely matches measured iridium levels in the K/Pg layer.
• The consistency between predicted and observed iridium levels supports the conclusion that the impactor was most likely a comet rather than an asteroid.
• The study concludes that a cometary origin best explains the geochemical and energetic constraints of the Chicxulub impact.