Coarse‐Grained Ripples Investigated by the Opportunity Rover on Meridiani Planum, Mars

Aeolian coarse‐grained ripples have been found in all regions investigated by Mars rovers: Meridiani Planum, Gusev crater, Gale crater, and Jezero crater. Therefore, it can be assumed that coarse‐grained ripples are one of the most common landforms on Mars. Studying their formation and evolution gives us the opportunity to determine past and current wind patterns. They are also crucial for understanding the formation and evolution of larger aeolian bedforms. Of all locations studied in situ on Mars, coarse‐grained ripples in extensive (∼100 km2) ripple fields were found only on Meridiani Planum. As coarse‐grained ripples on Mars are not well characterized in the literature, in this work, the morphometry, morphology, spatial distribution, and orientation of coarse‐grained ripples investigated along the 45 km long traverse of the Opportunity rover were analyzed. The obtained results allowed for a more precise definition of coarse‐grained ripples and for distinguishing three classes of coarse‐grained ripples on Meridiani Planum: small, medium, and large. The coarse‐grained ripple activity on Meridiani Planum is now limited due to low material supply, and the relatively strong induration of the ripple surfaces. Even though most of the coarse‐grained ripples on Meridiani Planum were formed thousands of years ago, some smaller coarse‐grained ripples were formed by modern winds. Plain Language Summary Ripples are sand ridges formed by wind. As ripples are very common on Mars, understanding their formation and evolution is very crucial not only for understanding the Martian environment but also for future Mars missions. Meridiani Planum is an equatorial plain on Mars that is covered by sand ripples. These ripples range in size from centimeters to decimeters, and their surface is made up of coarse sand particles (1–2 mm in diameter). The western part of Meridiani Planum was investigated by the Opportunity rover. Based on the rover's data and high‐resolution orbital images, the properties of ripples, including their size, shape, composition, distribution, and orientation, were analyzed. Meridiani Planum coarse‐grained ripples occur in three different size classes: small, medium, and large. They change very slowly as coarse particles armor their surface and because smaller (and therefore easier to carry by wind) sand particles are available only in small amounts, even though some of these ripples were formed relatively recently. Coarse‐grained ripples on Meridiani Pl