Giant impact basins trace the ancient equator of Mars

摘要

It is shown in this paper that five giant impact basins of Mars, Argyre, Hellas, Isidis, Thaumasia, and Utopia, are located on a single great circle. This suggests that the projectiles' orbital planes coincided with the equator of Mars at the time of impact. The projectiles were larger fragments of a heliocentric asteroid that broke apart as it entered the Roche limit of Mars. The mass of the asteroid was at least ～9.8 × 1020 kg, ～1.5 × 10~-3 times the mass of Mars.