@article{MarkusMorozArnoldetal.2018, author = {Markus, Kathrin and Moroz, Lyuba and Arnold, Gabriele and Henckel, Daniela and Hiesinger, Harald and Rohrbach, Arno and Klemme, Stephan}, title = {Reflectance spectra of synthetic Fe-free ortho- and clinoenstatites in the UV/VIS/IR and implications for remote sensing detection of Fe-free pyroxenes on planetary surfaces}, series = {Planetary and space science}, volume = {159}, journal = {Planetary and space science}, publisher = {Elsevier}, address = {Oxford}, issn = {0032-0633}, doi = {10.1016/j.pss.2018.04.006}, pages = {43 -- 55}, year = {2018}, abstract = {Both enstatite spectra are very bright in the VIS and NIR and show almost neutral to slightly bluish spectral slopes with a steep absorption in the UV. Very low iron in the enstatites (below similar to 0.04 wt\% FeO) already results in weak albeit noticeable absorptions in the VNIR between 0.4 and 0.9 mu m. Orthoenstatite and clinoenstatite are not distinguishable based only on their spectra in the VIS and NIR. At the Reststrahlen bands in the MIR a systematic difference in the number and exact position of local minima at similar to 10 mu m between clinoenstatite and orthoenstatite is evident. This can be used to discern between the polymorphs in this wavelength range. Additionally, we can distinguish between Fe-free low- and high-Ca pyroxenes in the MIR.}, language = {en} } @article{QuiricoMorozSchmittetal.2016, author = {Quirico, E. and Moroz, Liubov V. and Schmitt, B. and Arnold, Gabriele and Faure, M. and Beck, P. and Bonal, L. and Ciarniello, M. and Capaccioni, F. and Filacchione, G. and Erard, S. and Leyrat, C. and Bockelee-Morvan, D. and Zinzi, A. and Palomba, E. and Drossart, P. and Tosi, F. and Capria, M. T. and De Sanctis, M. C. and Raponi, A. and Fonti, S. and Mancarella, F. and Orofino, V. and Barucci, A. and Blecka, M. I. and Carlson, R. and Despan, D. and Faure, A. and Fornasier, S. and Gudipati, M. S. and Longobardo, A. and Markus, K. and Mennella, V. and Merlin, F. and Piccioni, G. and Rousseau, B. and Taylor, F.}, title = {Refractory and semi-volatile organics at the surface of comet 67P/Churyumov-Gerasimenko: Insights from the VIRTIS/Rosetta imaging spectrometer}, series = {Icarus : international journal of solar system studies}, volume = {272}, journal = {Icarus : international journal of solar system studies}, publisher = {Elsevier}, address = {San Diego}, organization = {Rosetta VIRTIS Team}, issn = {0019-1035}, doi = {10.1016/j.icarus.2016.02.028}, pages = {32 -- 47}, year = {2016}, abstract = {The VIRTIS (Visible, Infrared and Thermal Imaging Spectrometer) instrument aboard the Rosetta spacecraft has performed extensive spectral mapping of the surface of comet 67P/Churyumov-Gerasimenko in the range 0.3-5 mu m. The reflectance spectra collected across the surface display a low reflectance factor over the whole spectral range, two spectral slopes in the visible and near-infrared ranges and a broad absorption band centered at 3.2 mu m. The first two of these characteristics are typical of dark small bodies of the Solar System and are difficult to interpret in terms of composition. Moreover, solar wind irradiation may modify the structure and composition of surface materials and there is no unequivocal interpretation of these spectra devoid of vibrational bands. To circumvent these problems, we consider the composition of cometary grains analyzed in the laboratory to constrain the nature of the cometary materials and consider results on surface rejuvenation and solar wind processing provided by the OSIRIS and ROSINA instruments, respectively. Our results lead to five main conclusions: (i) The low albedo of comet 67P/CG is accounted for by a dark refractory polyaromatic carbonaceous component mixed with opaque minerals. VIRTIS data do not provide direct insights into the nature of these opaque minerals. However, according to the composition of cometary grains analyzed in the laboratory, we infer that they consist of Fe-Ni alloys and FeS sulfides. (ii) A semi-volatile component, consisting of a complex mix of low weight molecular species not volatilized at T similar to 220 K, is likely a major carrier of the 3.2 p.m band. Water ice contributes significantly to this feature in the neck region but not in other regions of the comet. COOH in carboxylic acids is the only chemical group that encompasses the broad width of this feature. It appears as a highly plausible candidate along with the NH4+ ion. (iii) Photolytic/thermal residues, produced in the laboratory from interstellar ice analogs, are potentially good spectral analogs. (iv) No hydrated minerals were identified and our data support the lack of genetic links with the CI, CR and CM primitive chondrites. This concerns in particular the Orgueil chondrite, previously suspected to have been of cometary origin. (v) The comparison between fresh and aged terrains revealed no effect of solar wind irradiation on the 3.2 mu m band. This is consistent with the presence of efficient resurfacing processes such as dust transport from the interior to the surface, as revealed by the OSIRIS camera. (C) 2016 Elsevier Inc. All rights reserved.}, language = {en} } @article{KappelArnoldHaus2016, author = {Kappel, David and Arnold, Gabriele and Haus, Rainer}, title = {Multi-spectrum retrieval of Venus IR surface emissivity maps from VIRTIS/VEX nightside measurements at Themis Regio}, series = {Icarus : international journal of solar system studies}, volume = {265}, journal = {Icarus : international journal of solar system studies}, publisher = {Elsevier}, address = {San Diego}, issn = {0019-1035}, doi = {10.1016/j.icarus.2015.10.014}, pages = {42 -- 62}, year = {2016}, abstract = {Renormalized emissivity maps of Themis Regio at the three surface windows are determined from 64 measurement repetitions. Retrieval errors are estimated by a statistical evaluation of maps derived from various disjoint selections of spectra and using different assumptions on the interfering parameters. Double standard deviation errors for the three surface windows amount to 3\%, 8\%, and 4\%, respectively, allowing geologic interpretation. A comparison to results from an earlier error analysis based on synthetic spectra shows that unconsidered time variations of interfering atmospheric parameters are a major error source. Spatial variations of the 1.02 mu m surface emissivity of 20\% that correspond to the difference between unweathered granitic and basaltic rocks would be easily detectable, but such variations are ruled out for the studied target area. Emissivity anomalies of up to 8\% are detected at both 1.02 and 1.18 mu m. At present sensitivity, no anomalies are identified at 1.10 mu m, but anomalies exceeding the determined error level can be excluded. With single standard deviation significance, all three maps show interesting spatial emissivity variations. (C) 2015 Elsevier Inc. All rights reserved.}, language = {en} } @phdthesis{Arnold2013, author = {Arnold, Gabriele}, title = {Spektrale Fernerkundung der terristrischen Planetoberfl{\"a}chen von Merkur, Venus und Mars vom visuellen bis in den infraroten Wellenl{\"a}ngenbereich}, address = {Potsdam}, pages = {573 S.}, year = {2013}, language = {de} }