Reconstruction of the Morasko meteoroid impact-Insight from numerical modeling

The Morasko strewn field located near Poznan, 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 degrees. 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 similar to 10 km s(-1). Environmental consequences of the Morasko impact event are very localized.