Mars Science Laboratory Curiosity Rover Megaripple Crossings up to Sol 710 in Gale Crater

Abstract

rover traveled across regolith-covered, rock-strewn plains that transitioned into terrains that have been variably eroded, with valleys partially filled with windblown sands, and intervening plateaus capped by well-cemented sandstones that have been fractured and shaped by wind into outcrops with numerous sharp rock surfaces. Wheel punctures and tears caused by sharp rocks while traversing the plateaus led to directing the rover to traverse in valleys where sands would cushion wheel loads. This required driving across a megaripple (windblown, sand-sized deposit covered by coarser grains) that straddles a narrow gap and several extensive megaripple deposits that accumulated in low portions of valleys. Traverses across megaripple deposits led to mobility difficulties, with sinkage values up to approximately 30% of the 0.50 m wheel diameter, resultant high compaction resistances, and rover-based slip up to 77%. Analysis of imaging and engineering data collected during traverses across megaripples for the first 710 sols (Mars days) of the mission, laboratory-based single-wheel soil experiments, full-scale rover tests at the Dumont Dunes, Mojave Desert, California, and numerical simulations show that a combination of material properties and megaripple geometries explain the high wheel sinkage and slip events. Extensive megaripple deposits have subsequently been avoided and instead traverses have been implemented across terrains covered with regolith or thin windblown sand covers and megaripples separated by bedrock exposures. C 2016 Wiley Periodicals, Inc.

Improving Slip Prediction on Mars Using Thermal Inertia Measurements

“…However, evidence suggests both depth and physical properties were important. For example, Arvidson et al [4] estimate that the properties of the sand at Dingo Gap were more traversable than at Hidden Valley. Higher GTS thermal inertia at Dingo Gap supports this claim.…”

“…Therefore, because particle size, density, and cementation strongly influence both traversability and thermal inertia, there is a strong correlation between traversability and thermal inertia. Similarly, as depth of surface sand increases thermal inertia [44] and traversability [4] both decrease. A correlation between the thermal properties of granular terrain and traversability has been demonstrated experimentally on Earth [13,12].…”

“…All three rovers have suffered significant delays caused both by excessive slip in hazardous sand and time wasted analyzing safe sand before successful traversal [4,50]. The most serious mobility problem was encountered by Spirit when its wheels fell through a thin cemented surface layer (duricrust) into weak, undetected sand.…”

Surface-based 3D measurements of small aeolian bedforms on Mars and implications for estimating ExoMars rover traversability hazards

“…While smaller examples were safely crossed by MER Opportunity, larger examples resulted in excessive wheel slippage, and could have led to a mission-ending situation (Arvidson et al, 2011). Even MSL, the most capable Mars rover currently operating, has found it hard to traverse aeolian features that appeared to be megaripples, sinking into one example at 'Moosilauke Valley' by about 30% of its 50 cm wheel diameter, and with slippage reaching~77% (Arvidson et al, 2017). Hence, understanding whether the majority of the aeolian bedforms are, or are not, traversable at a given landing site is essential, both in the first instance for landing site selection, and ultimately for efficient rover surface operations.…”

“…Hence, understanding whether the majority of the aeolian bedforms are, or are not, traversable at a given landing site is essential, both in the first instance for landing site selection, and ultimately for efficient rover surface operations. Although a variety of material properties-including notably grain size and degree of armouring by coarse grains-alter the traversability characteristics of bedforms (Arvidson et al, 2017), a knowledge of the size and shape of aeolian bedforms is a primary question for any given rover site.…”