Dunes and ventifacts are depositional and erosional geomorphic landforms found on Earth and on Mars. Both dunes and ventifacts are a product of aeolian processes and can be used to interpret wind regimes. Dunes respond and record modern wind flow, whereas ventifacts are an outcome of long-term aeolian weathering, creating features that reflect paleo wind regime. The presence of dunes and ventifacts on Mars provides the opportunity to evaluate modern and ancient Martian surficial processes and climatology. The dune and ventifact field at Mason Bay, Rakiura|Stewart Island, New Zealand, is used as a terrestrial analogue to study the relationship between short-term and long-term climate indicators, using Mars remote analysis techniques.

The outline of the central dune field at Mason Bay and individual parabolic dunes were mapped from aerial images (2003-2023) in ArcGIS Pro to ascertain dune orientation and track migration rate. Photogrammetric images were captured for 18 individual ventifacted clasts and 11 quadrats (1m x 1m squares) across the deflation surfaces. These images were used in Agisoft Metashape to create scaled 3D models of the real-world samples to measure and record clast height (z-axis), lithology, and macro and mesoscale features such as facets, grooves and pits. The 18 ventifact models were then georeferenced in CloudCompare where the orientation of ventifact features were measured and recorded.

The parabolic dunes at Mason Bay are oriented to the east (95°), migrating 113.5m on average between 2003 and 2023, with some years experiencing a higher rate of migration than others. At the eastern end of the field area, a sand lobe migrated 327m over the same period to the east-south-east (120°). A comprehensive analysis of 4447 clasts within the 11 quadrats revealed that 85% of clasts are ventifacted. Average clast height (z-axis) ranges from 0.5cm to 2.3cm across the deflation surfaces, with an average maximum clast height (z-axis) of 10.3cm. Comparisons were made between the 18 ventifact photogrammetric models on lithology, ventifact height (z-axis), small ventifacts on the deflation surface vs immobile ventifact outcrop, upwind vs downwind portions of the field and trisections of the field. The ventifact features across all 18 clasts revealed an average orientation of 279°, based on 1195 measurements. Ventifact feature orientations were found to be statistically similar between ventifacts on the deflation surface and the immobile ventifacted outcrop. Results found that the orientation of features on different lithologies were statistically similar, only varying by 2-3 degrees.

These findings reveal that the parabolic dunes at Mason Bay are reflecting a westerly wind which aligns with the orientation of ventifact features. This indicates that the wind regime at Mason Bay has not changed from the prevailing westerly. The eastern lobe, however, reflects the orientation of a sloping path created by an old dune phase. Both geomorphic features at Mason Bay align with recorded wind data, demonstrating that they are good indicators of wind flow and accurately record local wind regime.

Three factors were found to influence ventifact formation at Mason Bay, 1) grain size of the clast where coarser grained lithologies exhibited an overall rougher surface with a greater quantity of ventifact features compared to finer grained lithologies. The development and appearance of ventifact features were also deeper and wider on coarser grained lithologies, 2) deflation of near surface wind flow around topographic obstacles, resulted in the variation of ventifact feature orientation across the field, and 3) a combination of ventifact height (z-axis) and topographic elevation (asl) is the likely cause of an increase in ventifact feature depth and width up the windward face of a ventifacted outcrop.

These findings can directly inform on Martian research. Through crestline and horn orientation, Martian barchan dunes can be used to infer modern dominant wind directions and sediment transport. The presence of ventifacts indicate that aeolian abrasion has been the dominant process for some time, and with ventifact features oriented parallel to the most dominant wind, they can be used to infer local wind regime. The controls of ventifact formation at Mason Bay can inform on the formation and interpretation of Martian ventifacts, as well as sediment transport. The grain size of Martian rocks can be inferred from the observation of ventifact features, which create an overall rougher surface on coarse-grained lithologies. Observations of the whole ventifact should be made to reflect the variability of ventifact features, as observed in the change of feature morphology on the ventifacted outcrop in this study. The usefulness of remote sensing techniques at providing accurate representations of the real-world landforms ensures that they can be used in the place of in person field techniques for Mars research. This study demonstrates that sand dunes and ventifacts accurately record local wind regime and therefore, can be used confidently to interpret local wind regime on Mars. A difference in orientation between dunes and ventifact features indicates a change in local wind regime and potentially a shift in Martian atmospheric circulation.