Comparative geomorphology is a standard and highly useful approach in determining the origin of features seen on planetary surfaces. However, this approach sometimes can point interpretations into the wrong direction - the specific and sometimes highly unique conditions found on another planet cannot be neglected in the analysis! In particular, long, narrow grooves found on the slopes of martian sand dunes have been cited as evidence of liquid water via the hypothesis of melt-water initiated debris flows.
Dr. Diniega and her team proposed an alternative hypothesis: blocks of CO2 ice (AKA dry ice) blocks that form naturally on the dune surfaces each winter may fall onto and slide down the dune slope, carving out features such as those observed. To test this hypothesis, they experimented with dry ice blocks on terrestrial dunes and then compared the expected behavior of blocks on the Earth and Mars via a theoretical model. Their results demonstrated that CO2 blocks can move as natural "hovercrafts" on dune slopes on both Earth and Mars, and that such blocks on Mars can naturally create the unique features we see on Mars.