Mars - Wind streak production as related to obstacle type and size

The characteristics of wind streaks associated with Martian craters and hills in the size range of 100 m to 80 km (corresponding to obstacle heights of a few to several hundred meters) have been analyzed from Viking Orbiter images. Both dark erosional and bright depositional streaks form over the entire obstacle size range, but there are preferred obstacle sizes for producing streaks. Bright streaks form more readily in association with relatively smaller obstacles than do dark streaks. Small obstacles produce both types of streaks more effectively than do large ones. Hills produce streaks as effectively as do craters of comparable height. Alternative explanations of bright streak formation are evaluated in terms of their ability to account for these observations. The most satisfactory models invoke blocking of atmospheric flow downwind of an obstacle and consequent deposition of dust within the sheltered zone.