title: Cracks in Martian boulders exhibit preferred orientations that point to solar-induced thermal stress.
abstract: The origins of fractures in Martian boulders are unknown. Here, using Mars Exploration Rover 3D data products, we obtain orientation measurements for 1,857 cracks visible in 1,573 rocks along the Spirit traverse and find that Mars rock cracks are oriented in statistically preferred directions similar to those compiled herein for Earth rock cracks found in mid-latitude deserts. We suggest that Martian directional cracking occurs due to the preferential propagation of microfractures favourably oriented with respect to repeating geometries of diurnal peaks in sun-induced thermal stresses. A numerical model modified here with Mars parameters supports this hypothesis both with respect to the overall magnitude of stresses as well as to the times of day at which the stresses peak. These data provide the first direct field and numerical evidence that insolation-related thermal stress potentially plays a principle role in cracking rocks on portions of the Martian surface.
authors: Department of Geography and Earth Sciences, University of North Carolina at Charlotte, Charlotte, North Carolina 28223, USA.
authors: Martha-Cary
authors: MC
authors: Eppes
authors: Department of Electrical and Computing Engineering, University of North Carolina at Charlotte, Charlotte North Carolina 28223, USA.
authors: Andrew
authors: A
authors: Willis
authors: Lunar and Planetary Laboratory, University of Arizona, Tucson, Arizona 85721, USA.
authors: Jamie
authors: J
authors: Molaro
authors: Department of Geography and Earth Sciences, University of North Carolina at Charlotte, Charlotte, North Carolina 28223, USA.
authors: Stephen
authors: S
authors: Abernathy
authors: Department of Electrical and Computing Engineering, University of North Carolina at Charlotte, Charlotte North Carolina 28223, USA.
authors: Beibei
authors: B
authors: Zhou