TERRESTRIAL ANALOGS FOR MARTIAN YARDANGS: THE ARGENTINIAN ALTIPLANO AND THE LUT DESERT OF IRAN

Yardangs are elongate, wind-sculpted, erosional ridges. Because of their morphological similarity to ships hulls, groups of yardangs are known as fleets. Occurring across thousands of square kilometers on the Earth, Mars, and possibly Venus and Titan, yardang fleets represent a rare landscape type that owes its major characteristics to the persistent erosive actions of the wind. Since yardangs are uncommon in North American, European, and Australian deserts, they were long considered geomorphological “oddities” by western geologists, and were seldom investigated in depth. The discovery of widespread yardangs on Mars by Mariner 9 sparked renewed interest in terrestrial yardangs. Since this time, extensive yardang fleets have been catalogued in China, Chad, Egypt, Namibia, Iran, and Afghanistan, along with minor occurrences in Tunisia, Algeria, Libya, Saudi Arabia, Mongolia, and Kuwait. While yardangs are sculpted primarily by the wind, water can have an important effect on their morphologies. In particular, rainfall modifies yardangs by either creating gullies in their flanks, or armoring them with a carapace of clay through repeated downslope washing. Periodic flooding of yardang troughs can undercut yardang flanks and cause mass wasting events, or lead to the creation of hard, salty playa surfaces that inhibits further trough downcutting. In this contribution, we describe the differences between yardangs formed in a nearly waterless environment (the Argentinian altiplano) and contrast them with yardangs formed in progressively wetter environments, such as the Lut Desert of Iran, the Mojave Desert of California, and San Miguel Island of the California Channel Islands. Using these field observations as a guide, we apply the lessons learned to interpret diverse yardang morphologies present on Mars.