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tokens: minerals that formed in a water-rich environment, including phyllosilicates, sulfates, and hematite, which suggests changes in ancient aqueous environments. After exploring the top of Vera Rubin Ridge (VRR) in 2018, which mostly contains hematite signatures, the rover descended into a trough south of the ridge, dropping as much as 15 meters in elevation during the spring of 2019 to explore part of the clay-bearing unit, and Curiosity is currently investigating the clay-bearing unit on the side of Mount Sharp. Elemental abundances and mineralogical information has been obtained from the ChemCam, APXS, and CheMin instruments, which allows us to directly test the quantitative results from the orbital remote sensing data. Spectral unmixing modelling was performed on the CRISM single scattering albedo spectra to extract the abundances and grain sizes of both hydrous and anhydrous phases. Examples of spectral unmixing results over the hydrated sulfate and phyllosilicate units are shown in Fig. 6 . To investigate the spatial distribution of the secondary mineral abundances, we applied our spectral unmixing model to CRISM image HRL0000BABA to generate the mineral abundance map. Figure 7 a shows the distribution of the secondary phases mapped over Mount Sharp using the CRISM parameter map ( Milliken et al. 2010 ), and Fig. 7 b shows the results of the spectral unmixing analysis over the selected region enclosed in the white box in Fig. 7 a. From Fig. 7 b it is possible to resolve the hematite, phyllosilicate, and hydrated sulfate unit, and these units are consistent with the spatial distribution derived from the CRISM parameter map shown in Fig. 7 a. The spectral unmixing of the CRISM image cube over Gale indicates that there is 30% hematite, 5% phyllosilicates, and 20% hydrated sulfates. We note that the error of the retrieved abundance is around 5% following the error analysis approach used in Liu et al. (2016) . Fig. 7 Panel a : CRISM FRT0000BABA RGB mineral parameter map (red = Fe-minerals, green = Fe/Mg-clay minerals, blue = sulfates) overlain on CTX mosaic. Image adapted from Fig. 3 a of Milliken et al. (2010) . Panel b : Derived mineral abundance map over a region covering Curiosity’s traverse, outlined in the white box in Fig. 7 a. The derived mineral abundances from CRISM observations can be used to compare with the ground-truth data. Vera Rubin ridge (VRR) of Gale crater has the strongest spectral signature consistent with hematite detected from orbit, and the area has been explored by Curiosity rover intensively. Curiosity data show that hematite is present throughout most of the Murry formation and VRR, though it is more abundant in certain drill samples ( Rampe et al. 2019 ). The abundance of these iron oxides are around 20 wt%, as inferred from ChemCam and APXS instruments ( Milliken et al. 2019 ), and the value is slightly lower than what we derived from orbital data. In addition to abundance discrepancies, spatial distribution also