EP023-02
Topographic Controls on Yardang Morphology Revealed with High-Resolution Digital Elevation Models of Yardangs in the Altiplano-Puna, Argentina and the Medusae Fossae Formation, Mars
Topographic Controls on Yardang Morphology Revealed with High-Resolution Digital Elevation Models of Yardangs in the Altiplano-Puna, Argentina and the Medusae Fossae Formation, Mars
Wednesday, 9 December 2020: 10:34
Virtual
Abstract:
Yardangs are streamlined eolian erosional landforms that form in consolidated substrates on rocky planets with atmospheres. Terrestrial yardangs are restricted to deserts such as the Altiplano-Puna region of South America, which makes an excellent Mars analog due to its low rainfall, high winds, and volcanic bedrock. Yardangs occur there in welded and unwelded ignimbrites similar to the friable, low density, high porosity material that has been proposed to comprise the Medusae Fossae Formation on Mars. Although yardang sizes, shapes, and spacing are known to vary widely in several terrestrial materials, more work remains to determine the relative influence of material properties on yardang morphology compared to that of wind patterns and sediment loads. We show that parameterizing yardangs in this way informs their interpretation in unknown materials and wind regimes.
During two field seasons in 2018-19, we obtained drone-based imagery of yardangs in the Altiplano-Puna for comparison with images of yardangs in the Medusae Fossae Formation obtained by the HiRISE camera. Both terrestrial and martian datasets were compiled into digital terrain models used to extract and parameterize yardang shapes. The terrestrial data was overlain in select locations with material properties such as density, porosity, and compressive strength obtained in-situ during the field seasons.
We found that the material properties we collected were correlated with the median sizes of yardangs in different areas, as well as yardang height and side slope angles. Within each area, smaller yardang shapes and sizes were associated with upwind obstructions and leeward sloping interyardang corridors, rather than yardang sizes only covarying with material properties. The distribution of sizes and shapes in Mars yardangs was most similar to terrestrial megayardangs (kilometers in size), implying that the Mars yardangs have an erosion resistance comparable to welded ignimbrites under Altiplano-Puna conditions, but likely lower strength due to differences in mass wasting and saltation caused by lower gravity on Mars. These datasets reflect a growing understanding of the unifying processes controlling yardang formation in differing materials on different planets.
During two field seasons in 2018-19, we obtained drone-based imagery of yardangs in the Altiplano-Puna for comparison with images of yardangs in the Medusae Fossae Formation obtained by the HiRISE camera. Both terrestrial and martian datasets were compiled into digital terrain models used to extract and parameterize yardang shapes. The terrestrial data was overlain in select locations with material properties such as density, porosity, and compressive strength obtained in-situ during the field seasons.
We found that the material properties we collected were correlated with the median sizes of yardangs in different areas, as well as yardang height and side slope angles. Within each area, smaller yardang shapes and sizes were associated with upwind obstructions and leeward sloping interyardang corridors, rather than yardang sizes only covarying with material properties. The distribution of sizes and shapes in Mars yardangs was most similar to terrestrial megayardangs (kilometers in size), implying that the Mars yardangs have an erosion resistance comparable to welded ignimbrites under Altiplano-Puna conditions, but likely lower strength due to differences in mass wasting and saltation caused by lower gravity on Mars. These datasets reflect a growing understanding of the unifying processes controlling yardang formation in differing materials on different planets.