The mosaic comprises four HiRISE (High Resolution Imaging Science Experiment, McEwen et al., 2007) images: ESP_035141_1990_RED, ESP_037330_1990_RED, ESP_037607_1990_RED and PSP_002743_1985_RED. Individual images were co-registered to a single CTX (Context Camera) ortho-image scene G12_022957_1985_XN_18N282W (5 m/pixel) (Malin et al., 2007), which was itself co-registered to the HRSC Mars Chart (HMC_13E10) ortho-rectified image mosaic (12.5 m/pixel) (Gwinner et al., 2016). Co-registration was performed using the “Georeferencing” tool in ArcGIS software with manually selected control points and spline transformations. Following co-registration, brightness normalization was applied to harmonize the individual HiRISE images with the reference CTX image, thereby eliminating albedo discontinuities at image boundaries and achieving a visually homogeneous mosaic. Each HiRISE scene was subdivided into a grid of 12 × 36 patches (x-direction × y-direction), and the average brightness was calculated for each patch along with the corresponding patch from the reference CTX image. A normalization ratio for each patch was computed by dividing the reference brightness value by the original image brightness value. Transitions between patches were interpolated to eliminate visible boundary effects. Finally, the normalized images were mosaicked using standard GDAL command-line tools. The brightness adjustment algorithm was implemented in Python.
