Reconstruction of the Morasko meteoroid impact—Insight from numerical modeling

Abstract

The Morasko strewn field located near Poznań, Poland comprises seven impact craters with diameters ranging from 20 to 90 m, all of which were formed in glacial sediments around 5000 yr ago. Numerous iron meteorites have been recovered in the area and their distribution suggests a projectile with the trajectory from NE to SW. Similar impact events producing crater strewn fields on average happen every 500 yr and pose a serious risk for modern civilization, which is why it is of utmost importance to study terrestrial strewn fields in detail. In this work, we investigate the Morasko meteoroid passage through the atmosphere, the distribution of its fragments on the ground, and the process of forming individual craters by means of numerical modeling. By combining atmospheric entry modeling, Pi‐group scaling of transient crater size and hydrocode simulations of impact processes, we constructed a comprehensive model of the Morasko strewn field formation. We determined the preatmospheric parameters of the Morasko meteoroid. The entry mass is between 600 and 1100 tons, the velocity range is between 16 and 18 km s−1, and the trajectory angle is 30–40°. Such entry velocities and trajectory angles do not deviate from typical values for near‐Earth asteroids, although the initial mass we determined can be considered as small. Our studies on velocities and masses of crater‐forming fragments showed that the biggest Morasko crater was formed by a projectile about 1.5 m in diameter with the impact velocity ~10 km s−1. Environmental consequences of the Morasko impact event are very localized.

Geology of the Morasko craters, Poznań, Poland—Small impact craters in unconsolidated sediments

“…) arguments, supported by numerical modeling results (Bronikowska et al. ). The study allows us to identify three primary geological indicators supporting the impact origin.…”

“…The modeled ejecta blanket thickness from the numerical model by Bronikowska et al. () is provided for comparison. Note the logarithmic vertical scale.…”

“…Indeed, such features may be difficult to find, as the numerical modeling results show (Bronikowska et al. ) that the amount of shocked target material was low and is most likely located mainly under crater A, below the infill of water and lacustrine sediments.…”

“…Nevertheless, he noted that his conclusions are “not the final and univocal.” The latest studies, including numerical modeling of the fall of the Morasko meteorite (Bronikowska et al. ), a morphometric analysis of the Morasko crater field (Włodarski et al. ), and age estimations for the impact of the Morasko meteorite (Szczuciński et al.…”

Holocene paleohydrological reconstruction of Lake Strzeszyńskie (western Poland) and its implications for the central European climatic transition zone

“…The latter might coincide with the nearby Morasko iron meteorite shower that took place before 4.9-5.3 kyr cal BP (Stankowski 2008) and that resulted in the formation of several impact craters up to 100 m wide located approximately 5.7 km NE of Lake Strzeszyńskie. However, a lack of concurrent changes in sediment characteristics reveals that the environmental consequences of this event were probably restricted, as also suggested by the meteorite impact numerical modelling (Bronikowska et al 2017).…”