Occam’s Razor and Mars:
Hertzian fractures, Gale and other domed and fractured craters.
by James Byous
Gale crater is a 155 km diameter impact crater that is at its center a blend between a compound and a coved-shield-type Hertzian cone (HC). Its features include a tilted peak and dome and dual wings on the east and west in arcs running north to south which are typical of low-angle impacts that create Hertzian fractures (HF) in glass and ceramics. Gale’s mound strata were laid over the years and in the flash of one meteoric impact the sub-surface cone was created. The bowl-shaped crater area eroded to a level below the original crater floor as wind quarried and dispersed the dust of the surrounding upper plane. Around the impact-compressed cone-mound of Mount Sharp (Aeolis Mons) wind forces carved out and carried away uncompressed material enlarging the bowl to reveal the lower mound. Gale Crater is now eroded well below the original surface by aeolian reduction revealing the totality of the current structure. In the future Gale crater could include a still deeper bowl and taller mound as more material is extracted. The main peak-shaped point-of-impact (POI) of Mount Sharp stands at ~5 km above aqueous and aeolian deposited crater-floor strata that is comprised of sediment rock and dunes. A larger, second point-of-impact peak stands ~20 kilometers to the north forming the main upper mound that stands above the winged ridges to the ESE and WSW. This wider dome POI area on the mound’s center-north quadrant suggests at least two coincidental impacts by a fragmented projectile. Arroyos and canyons that cut through the mound hold similarities to features found in other Hertzian cones. The mound area of Mount Sharp contains the five classic features found in many HC and HF structures; point of impact, mirror, mist, hackles region and Wallner undulation lines. Yardang-shaped hillocks along the body of the mound appear to be eroded hackles as can be found on compound HC structures. Features formed by projectile impacts that are similar in shape to Mount Sharp can be found in the windshields of cars in countless mall and market parking lots around the world. Like the ding in a glass window, Mount Sharp is the structure of a common Hertzian fracture -- a projectile-impact-induced stack of compacted crystalline material. Gale is only one of innumerable and similarly created structures on Mars and other rocky planets and moons in the universe.