Mapping evaporitic surfaces in the Atacama Desert using radar–spectral fusion: a remote sensing approach for terrestrial and planetary analogs

Evaporite mapping in hyperarid regions is crucial for understanding surface hydrology, salt crust dynamics, and environmental change. Terrain classification in these settings is hindered by spectral overlap among surface types and limited remote sensing coverage. To our knowledge, no previous workflow has combined Sentinel-1 radar data with Sentinel-2 indices for mapping evaporites in a Mars-analog environment. We developed a lightweight, rule-based fusion of horizontal transmit – horizontal receive (HH)-polarized Sentinel-1 backscatter with the Normalized Difference Water Index (NDWI) and Normalized Difference Snow Index (NDSI) from Sentinel-2, optimized for simplicity and low computational demand. Applied to a salt flat in northern Chile, moist salts accounted for ~67% and dry evaporites for ~5% of the area. The fused method achieved an overall agreement of more than 80% and F1-scores above 0.75, improving accuracy by 10–15% compared to spectral-only approaches. This sensor-independent framework supports efficient mapping of evaporitic surfaces in data-limited environments. It is directly transferable to planetary surface analysis, including analog studies and autonomous terrain triage during mission operations.