Figure 11 . MAHLI color
image of the two APXS Fleurac targets is shown. Circles represent the
approximate fields of view of the APXS as deployed onto the surface.
Fleurac contains a higher fraction of what appears to be cobble-size
fragments of local bedrock whereas Fleurac_offset has a lower fraction.
Both likely contain smaller local fragments mixed with sands from the
Sands of Forvie. Image credit: NASA/JPL-Caltech/MSSS.
Deconvolution of the paired Fleurac measurements followed VanBommel et
al. (2016, 2020), with deconvolution at the spectral level (e.g.,
VanBommel et al., 2019a, 2019b) as opposed to the derived oxides (e.g.,
VanBommel et al. 2016, 2017; Arvidson et al., 2016b; Stein et al.,
2018). This approach provided superior accuracy in the final results;
variability in sample relief was determined to be inconsequential
(VanBommel et al., 2017). The spectral parameters within the
deconvolution of the hypothesized wind-blown sand endmember were largely
constrained due to numerous previous sand measurements where the
contribution of locally disaggregated bedrock was assumed to be minimal
(VanBommel et al., 2017). The presumed local regolith endmember was
entirely unconstrained, aside from a closure requirement. The
deconvolution analysis modeled the primary Fleurac target with 35%
blocky material and 65% wind-blown sand, whereas the secondary offset
target captured a combination of 10% blocky material and 90%
wind-blown sand. These percentages are consistent with visual estimates
from MAHLI images acquired with each APXS measurement location (Figure
11). The retrieved composition of the presumed locally derived regolith
endmember most closely matched the composition of the nearby rock target
Limeyrat_DRT, acquired one sol prior at the same investigation site
(O’Connell-Cooper et al., 2022; Figure 10). A ratio plot of oxide
compositions relative to a nearby sand composition shows that the
calculational procedure was physically meaningful (Figure 12).