MINERALOGICAL MAPPING OF THE AC-AH-08 NAWISH QUADRANGLE OF CERES FROM NASA-DAWN MISSION

VIR (Visible-Infrared Mapping Spectrometer, De Sanctis et al., 2011), on board the NASA/DAWN mission, is an imaging spectrometer that analyzes the reflected light of Ceres covering the 0.25–5.1 µm (visible and near infrared) wavelengths range with the instantaneous field of view (IFOV) of 250 µrad. In this study we make use only of the IR channel data due to the absence of significant spectral features in the visible. The study is limited to quadrangle Nawish (144°E<LON<216°E; 22°S<LAT<22°N) analyzing Ceres’ spectra of HAMO rotational phase.

At a global scale, the preliminary spectral analysis reveals the presence of absorptions at ̴2.73, ̴3.06, ̴3.3 and ̴3.96 µm. Recently this set of bands has been interpreted as a mineral assemblage of ammoniated-phyllosilicates, Mg-phyllosilicates, carbonates, and dark material (Ammannito et al., 2016). We have used different spectral indices in order to discriminate different terrains. The results show that there is not a variety in the spectral composition, but only a variety in the values of the spectral parameters used. Some peculiar values are found in some locations. For example, bright spots inside Dantu crater and an unnamed crater located at 200.74°E and 20.57°S show the deepest bands at ̴4 µm suggesting terrains rich in carbonates. An enrichment in phyllosilicate composition is present outside Nawish crater as inferred from the increasing band depth at ̴2.7 µm. On the basis of the band depth at ̴3.06 µm (BD3000), attributed to ammonia-bearing species (De Sanctis et al., 2015), the terrains can be divided in two regions. The first corresponds to the cratered plains and cratered highlands and shows low-intermediate values, while the other terrains show high values.

Acknowledgements

This work is supported by the Italian Space Agency (ASI). VIR was funded and coordinated by the Italian Space Agency, with the scientific leadership of the Institute for Space Astrophysics and Planetology, Italian National Institute for Astrophysics, Italy. Support of the Dawn Science, Instrument, and Operation Teams is gratefully acknowledged.

References

Ammannito, E. et al. (2016).

De Sanctis, M.C. et al., SSR 163 (2011).

De Sanctis, M.C. et al., Nature 528 (2015).