Trajectory of Asteroid Aletai Shows Unique Stone-Skipping Behavior

Map showing the location and masses of where Aletai falls were recovered. Credit: Li et al., 2022.

Meteoroids are small bodies of extraterrestrial materials that enter Earth’s atmosphere, creating streaks of light known as meteors. If they survive passage through the atmosphere and land on Earth, they become meteorites and are deposited in strewn fields. A strewn field, the area over which meteorites are dispersed from a single fall, is typically dozens of kilometers in length. Since meteorite falls can deliver large amounts of kinetic energy and are therefore potentially hazardous, studying the physical properties, trajectory, velocity, and angle of entry of a meteoroid is of prime importance.

The Aletai meteorite is an iron meteorite, 74 tons of which have been recovered in the Aletai region in the Xinjiang Province in China. The total length of the Aletai strewn field is 430 kilometers, the longest known to date. To understand how this impact event generated such a widespread distribution of meteorite fragments, Ye Li and colleagues from the Purple Mountain Observatory, Chinese Academy of Sciences, combined analyses of the petrology and geochemistry of the meteorite, with radionuclide analyses and numerical modeling, to estimate the depths from which these fragments were derived in the meteoroid. This led to estimates of the mass of the meteoroid as well as its velocity and angle of entry. 

Results of this work indicate that the Aletai meteoroid, which consists primarily of the mineral kamacite (Fe-Ni alloy), had a shallow angle of entry into Earth’s atmosphere. The numerical modeling of its trajectory, based on mass, velocity, and angle of entry, indicate that a behavior similar to stone-skipping was responsible for the unusual length of the strewn field. Stone-skipping trajectories could result in the long-duration dissipation of a meteoroid’s energy into the atmosphere instead of into the ground, making it potentially less hazardous. These new results could help determine whether other large strewn fields are a result of similar dynamics in Earth’s atmosphere. READ MORE