The Carancas meteorite impact crater, Peru: Geologic surveying and modeling of crater formation and atmospheric passage

Abstract

It is the smallest, youngest, and one of two eye-witnessed impact crater events on Earth. The impact violated the hitherto existing view that stony meteorites below a size of 100 m undergo major disruption and deceleration during their passage through the atmosphere and are not capable of producing craters. Fragmentation occurs if the strength of the meteoroid is less than the aerodynamic stresses that occur in flight. The small fragments that result from a breakup rain down at terminal velocity and are not capable of producing impact craters. The Carancas cratering event, however, demonstrates that meter-sized stony meteoroids indeed can survive the atmospheric passage under specific circumstances. We present results of a detailed geologic survey of the crater and its ejecta. To constrain the possible range of impact parameters we carried out numerical models of crater formation with the iSALE hydrocode in two and three dimensions. Depending on the strength properties of the target, the impact energies range between approximately 100-1000 MJ (0.024-0.24 t TNT). By modeling the atmospheric traverse we demonstrate that low cosmic velocities (12-14 kms −1 ) and shallow entry angles (<20°) are prerequisites to keep aerodynamic stresses low (<10 MPa) and thus to prevent fragmentation of stony meteoroids with standard strength properties. This scenario results in a strong meteoroid deceleration, a deflection of the trajectory to a steeper impact angle (40-60°), and an impact velocity of 350-600 ms −1 , which is insufficient to produce a shock wave and significant shock effects in target minerals. Aerodynamic and crater modeling are consistent with field data and our microscopic inspection. However, these data are in conflict with trajectories inferred from the analysis of infrasound signals.

Shock metamorphism and impact melting in small impact craters on Earth: Evidence from Kamil crater, Egypt

“…(); (3) Kenkmann et al. (); (4) Miura and Kato (); (5) Kofman et al. (); (6) This work; (7) Dietz (); (8) Smith and Hodge (); (9) Bunch and Cohen (); (10) Chao et al.…”

The Whitecourt meteorite impact crater, Alberta, Canada

“…With the proposed impact angles, velocities, and meteoroid and target material properties it is possible to estimate the radius of the meteoroid at the time of impact. In a manner similar to that of Kenkmann et al. (2009), scaling laws based on the theoretical analysis of cratering mechanics by Holsapple and Schmidt (1987), Housen et al.…”

Cosmogenic radionuclides in L5 and LL5 chondrites from Queen Alexandra Range, Antarctica: Identification of a large L/LL5 chondrite shower with a preatmospheric mass of approximately 50,000 kg

“…Finally, the recent impact of the Carancas H chondrite, which produced a 14 m wide crater in Peru, showed that the atmospheric fragmentation process may be strongly dependent on entry velocity and angle, in addition to physical strength (Kenkmann et al. 2009).…”