Stunning HiRISE image reveals sand dunes trapped inside mysterious crater on Mars

This stunning visual, captured by the High-Resolution Imaging Science Experiment (HiRISE) aboard NASA's Mars Reconnaissance Orbiter (MRO), shows the workings of the Martian winds trapped inside an unnamed crater in southern Terra Cimmeria of the Red Planet.

The Southern Highlands of Mars are known for their abundance of craters, many of which are adorned with sand dunes. The ongoing mapping efforts by HiRISE aim to unravel the activity levels of these dunes. Observations suggest that the dunes in these craters exhibit a mix of characteristics, with some actively advancing while others seem to have become frozen in place.

This HiRISE image will be meticulously compared to a previous photograph, enabling scientists to discern any changes that have occurred since 2008.

The sand dunes stand out prominently against the bright background, manifesting as large, branched ridges and dark patches, particularly in the northwest corner. Additionally, there are indications of two other wind-related processes at play - smaller, brighter ridges can be seen lining the crater floor in evenly spaced rows. These intriguing formations, known as "transverse aeolian ridges" (TARs), are windblown deposits that are more commonly observed in the Martian tropics. Faint and irregular dark lines traverse the dunes and TARs, representing the tracks left behind by dust devils, which sweep across the surface during the southern summer.

Scientists aim to unravel the chronological sequence of these processes by looking at the picture more closely.

For the majority of the image, the dark sand dunes bury the bright TARs, which means that the dunes are younger than the TARs. However, an intriguing exception arises in the case of the southernmost dune visible in the picture. In this case, the TARs appear to extend into the dune and merge with ripples on its surface, suggesting that the TARs might actually be younger than the dunes.

To resolve this conundrum, a meticulous examination of an enhanced color cutout is required, according to the HiRISE team. The TARs exhibit a brighter and redder hue compared to the sand dunes in the enhanced color cutout. This distinct color persists on the crests of the TARs as the sand encroaches, progressively burying the valleys, slopes, and eventually the TAR crests. This observation reveals that the unusual appearance of the dune margin is caused by burial and exposure of the older TARs by the younger sand. Additionally, by tracing the tracks of dust devils crisscrossing over the dunes, it becomes apparent that the dust devils are younger than the dunes themselves.

The HiRISE team concludes that the TARs were the first to emerge, followed by the dunes, and finally, the dust devils - likely occurring within the past few months. This sequence provides invaluable insights into the dynamic interplay between Martian winds and the landscape. 

HiPOD: Which Came First?The workings of the Martian winds are visible in this image of sand dunes trapped inside an unnamed crater in southern Terra Cimmeria. https://t.co/WlohV0Twl4NASA/JPL-Caltech/UArizona#Mars #science pic.twitter.com/HdeP10jXpQ

— HiRISE: Beautiful Mars (NASA) (@HiRISE) May 13, 2023