Campo del Cielo modeling and comparison with observations: I. Atmospheric entry of the iron meteoroid

Abstract

This paper presents an attempt to reconstruct the Campo del Cielo (CdC) impact event, that is, to estimate the preatmospheric mass and velocity of the iron meteoroid and pre-impact parameters of its fragments allowing formation of funnels and impact craters. The goal of this study is to improve the understanding of the effects small-scale iron meteoroids can have on the Earth's surface. We model the meteoroid's atmospheric flight taking deceleration, ablation, and fragmentation into account, and then compare the results with available observations. We found that a fragment's velocity near the surface should be <1 km s −1 in order to form a funnel with an intact meteorite inside. The estimates of preatmospheric (at an altitude of 100 km) parameters of the CdC impact event are as follows: minimal mass of 7500-8500 t, which corresponds to a diameter range of 12.2-12.8 m; maximum entry angle above the atmosphere of ~16.5°and velocities of 14.5-18.4 km s −1 , which is close to the one most frequently reached by Near-Earth objects (NEOs). Near the surface, the largest fragments with a mass of 400-1500 t and velocities of 4-7 km s −1 form impact craters whereas fragments with a mass <31 t and velocities <1 km s −1 form funnels. Masses <3 t are not included in our simulations. Their total mass is 280-460 t at the point of disruption but <110 t on the Earth's surface. These numerous small fragments are dispersed over a large area and are very popular among meteorite hunters and dealers. In spite of all the observed crater location/size data and impactor velocity limits from the models, there are far more free parameters than constraints. As a result, any values for preatmospheric mass, velocity, and entry angle are merely representative or limitative as opposed to true values.

Campo del Cielo modeling and comparison with observations: II. Funnels and craters

“…In this study, we explore the influence of input parameters such as impact velocity and target porosity on the funnel's geometry. The ultimate purpose of this study is to find plausible impact scenarios of the Campo del Cielo event consistent with observations (Cassidy & Renard, 1996; Vesconi et al., 2011) and with the atmospheric entry model (Schmalen et al., 2022).…”

“…We chose two large elliptical craters for this analysis: Hoyo de la Cañada and Laguna Negra (Table 5). For each crater, we consider two possible impact scenarios corresponding to meteoroid velocities at the altitude of fragmentation of 14 and 18 km s −1 (Schmalen et al., 2022 for detail), which we call Scenarios I and II, respectively.…”

“…The high‐resolution zone consists of 140 × 35 × 65 cells at shallow angles and 100 × 35 × 100 at 90°‐angle scenario in x ‐, y ‐, and z ‐direction, respectively (i.e., horizontal direction as the ground projection of the projectile, the cross‐range direction, and the vertical direction). For a shallow impact angle of 13°, we also model the formation of the Hoyo de la Cañada and Laguna Negra impact craters assuming impact velocities of 5–6.7 km s −1 in agreement with the atmospheric entry model (Schmalen et al., 2022). The high‐resolution zone consists of 250 × 80 × 150 cells in x ‐, y ‐, and z ‐direction, respectively.…”

“…To simulate the atmospheric motion of fragments from the projectile, we use an atmospheric entry model as presented by Passey and Melosh (1980) and later modified by Artemieva and Shuvalov (2001) and Schmalen et al. (2022). The model describes ablation and deceleration of the meteoroid in the atmosphere by a set of differential equations.…”

“…The strewn field consists of four elliptical depressions (remnants of impact craters) with diameters of 65–115 m and numerous penetration funnels with fragments of Campo del Cielo meteorites inside. The largest excavated fragment Gancedo weighs 30.8 t. The list of impact craters, penetration funnels, and the Campo del Cielo strewn field map can be found in early publications (Cassidy & Renard, 1996; Vesconi et al., 2011) as well as in our recent publication (Schmalen et al., 2022).…”