5 - Conclusion

High resolution X-band radar images of terrestrial linear dunes and mega-yardangs can help to better interpret the radar signature of similar structures that are likely to exist on the surface of Titan. Using a simple surface scattering model combined with topography data, we accurately reproduced the radar backscattering profiles of linear dunes (Egypt and Namibia) and mega-yardangs (Iran and Chad), thus establishing a relationship between the radar radiometry and the morphology and nature of imaged structures.

Applying this new understanding of the radar scattering process to the interpretation of Cassini RADAR data, we have shown that both Egyptian and Namibian-type dunes are present in the T8 flyby acquisition of the Belet Sand Sea, i.e. interdune regions there can be either sand-covered or not. This result should be taken into account for future studies of the equatorial dune fields present on Titan.

We have also shown that two radar-bright structures, observed during the T64 and T83 flyby acquisitions, are very likely to be the first mega-yardangs observed on Titan. Such erosional structures could be the remnants of past lake basins at mid-latitude, formed when Titan’s climate was different, and need for further studies to understand their origin.

As previously noticed by other authors, both dunes and yardangs on Titan present a much stronger radar return than their terrestrial counterparts, indicating that some additional scattering processes, such as volume scattering in an heterogeneous or porous material, occur on Titan.