Grand canyons on the Moon

Abstract

High energy streams of rock ejected from the Schrödinger impact basin carved two canyons in the lunar crust that are comparable in size to the Grand Canyon of North America. Here we use photogeologic mapping of those canyons and related impact ejecta deposits to show the trajectory of the impacting asteroid or comet, which produced an asymmetrical pattern of crater excavation and transport of ejected debris. The flow directions of that ejected debris and the speed of its subsequent impact with the lunar surface are calculated, as is the energy that carved the canyons in less than ten minutes. The study implies that most of the excavated debris was ejected away from the lunar south pole, minimizing the amount of debris that covers the > 4 billion year old units that will be explored by Artemis astronauts.

Fig. 1. Schrödinger impact basin.

a Orbital view of the Schrödinger peak-ring impact basin and two radiating canyons carved by impact ejecta. NASA\SVS\Ernest T. Wright. b Azimuthal Equidistant Projection of the Moon LRO LROC WAC Global Morphology Mosaic 100 m v3 (100 meters/pixel), centered on the Schrödinger basin, with the continuous ejecta blanket outlined (beige, after ref. ) and radial secondary crater rays (red). Vallis Schrödinger and Vallis Planck (see Fig. 3 for close-up views) intersect near the southern rim of the basin (white point). The size of the point indicates the uncertainty. The projected bearing of the primary impactor (yellow) runs through the point of intersection and the basin center. A third unnamed feature extends in an uprange direction.

Fig. 2. Comparison of canyon cross-sections.

a Width and depth of the Grand Canyon along the Bright Angel hiking trail from the south to the north rim (annotated in Supplementary Fig. 4). b Width and depth of Vallis Planck. The cross-section of Vallis Schrödinger is in Supplementary Fig. 6. Colors show 500 m elevation steps.

Fig. 3. Canyon rays.

Deepest sections of Vallis Schrödinger (a and b) and Vallis Planck (c and d) without and with identified craters. Green circled craters are clearly defined by their eroded crater rims, while yellow circled craters are inferred from the terrain and are not used in the crater scaling calculations. A wall of Valles Planck (lower left of c and d) appears to have collapsed into the canyon. Location of Supplementary Fig. 6 and Fig. 2 transects are shown (b and d), respectively.

Fig. 4. Parameters of ballistic flight.

Secondary impact velocities (red) and calculated secondary projectile diameters (blue) for Vallis Schrödinger (round symbols) and Vallis Planck (triangular symbols), assuming a 30° flight trajectory, with vertical bars on the symbols representing a range produced by flights from 20 to 45°. Black dashed line is a fit to the secondary impact velocity symbols. The Gray dashed line is the approximate extent of the continuous ejecta blanket.