¹Joshua T.S.Cahill, ¹David T.Blewett, ²Nhan V.Nguyen, ²Alex Boosalis, ³Samuel J.Lawrence, ¹Brett W.Denevi
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2018.07.008]
¹Johns Hopkins Applied Physics Laboratory, Laurel, MD 20723, USA
²National Institute of Standards and Technology, Gaithersburg, MD, USA
³NASA-Johnson Space Center, Houston, TX, USA
Copyright Elsevier

We report new measurements of the optical constants of iron and nickel metal in the ultraviolet, visible, and near-infrared portions of the electromagnetic spectrum (∼0.16 to 3.59 μm), building upon the measurements of Cahill et al. (2012). These values were determined from metal films vapor-deposited onto fused-silica prisms. Our measurement of optical constants employed ellipsometry performed within the prism, sensing the side of the metal film unexposed to the ambient atmosphere. The data we report have important implications for modeling planetary reflectance and emittance spectra, especially in relation to space-weathering effects observed in remotely sensed data for the surfaces of the Moon, Mercury, and asteroids.

¹F.G.Carrozzo et al. (>10)
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2018.07.013]
¹Istituto di Astrofisica e Planetologia Spaziali, INAF, Via del Fosso del Cavaliere 100, 00133 Roma, Italy
Copyright Elsevier

Quadrangle Ac-H-08 Nawish is located in the equatorial region of Ceres (Lat 22°S-22°N, Lon 144°E- 216°E), and it has variable mineralogy and geology. Here, we report on the mineralogy using spectra from the Visible and InfraRed (VIR) mapping spectrometer onboard the NASA Dawn mission. This quadrangle has two generally different regions: the cratered highlands of the central and eastern sector, and the eastern lowlands. We find this dichotomy is also associated with differences in the NH4-phyllosilicates distribution. The highlands, in the eastern part of the quadrangle, appear depleted in NH4-phyllosilicates, conversely to the lowlands, in the north-western side. The Mg-phyllosilicates distribution is quite homogeneous across Nawish quadrangle, except for few areas. The 2.7-µm band depth is lower in the south-eastern part, e.g. in the Azacca ejecta and Consus crater ejecta, and the band depth is greatest for the Nawish crater ejecta, and indicates the highest content of Mg-phyllosilicates of the entire quadrangle. Our analysis finds an interesting relationship between geology, mineralogy, topography, and the age in this quadrangle. The cratered terrains in the highlands, poor in NH4 phyllosilicates, are older (̴2 Ga). Conversely, the smooth terrain, such as with Vindimia Planitia, is richer in ammonia-bearing phyllosilicates and is younger (̴1 Ga). At the local scale, Ac-H-8 Nawish, displays several interesting mineralogical features, such as at Nawish crater, Consus crater, Dantu and Azzacca ejecta, which exhibit localized Na-carbonates deposits. This material is superimposed on the cratered terrains and smooth terrains and shows the typical depletion of phyllosilicates, already observed on Ceres in the presence of Na-carbonates.

¹Sara S. Russell, ²Harold C. Connolly Jr., ³Alexander N. Krot (Editors)
Cambridge University Press  Link to Book [doi.org/10.1017/9781108284073]
¹Natural History Museum, London
²Rowan University, New Jersey
³University of Hawaii, Manoa

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