The oblique impact Hale and its consequences on Mars

Highly oblique impacts represent a rare and special class of impact events manifested as elliptical craters preserved on present-day planetary surfaces. Crater excavation in highly oblique impacts differs from that of standard vertical impacts due to early time asymmetries imparted by the downrange-directed coupling of energy between the projectile and target. Such asymmetries are preserved as scouring and mobilized surface materials produced by high-velocity, low-angle ejecta and blast winds along the initial impact trajectory axis downrange. Subsequent deposition of resulting melt-rich products occurs in the form of concentrated strewnfields located downrange from the impact. The distinct nature of these distal strewnfields is separate from later time, more proximal ejecta accumulations and generally allows connecting these specific deposits with their parent crater. The present study involves a three-dimensional computational impact simulation (modeled using the CTH shock physics hydrocode) of an event similar to the impact that produced the elliptical Hale impact crater on Mars (125 km x 150 km diameter crater located at 36 degrees S, 36 degrees W). Results generally capture the predicted patterns indicative of highly oblique impacts. Evidence is presented for correlated distal strewnfields located downrange from Hale that coincide with prominent low-albedo surface deposits and wind streaks on the present-day Martian surface, thereby providing implications for possible identification for other dark glassy strewnfields as well as impact-generated winds on Mars.