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Optical alteration of complex organics induced by ion-irradiation: 1. Laboratory experiments suggest unusual space weathering trend.

Moroz, L. V. and Baratta, G. and Strazzulla, G. and Starukhina, L. V. and Dotto, E. and Barucci, M. A. and Arnold, G. and Distefano, E. (2004) Optical alteration of complex organics induced by ion-irradiation: 1. Laboratory experiments suggest unusual space weathering trend. Icarus: International Journal of Solar System Studies, 170, pp. 214-228.

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Abstract

Most ion irradiation experiments relevant to primitive outer Solar System objects have been performed on ice and silicate targets. Here we present the first ion irradiation experiments performed on natural complex hydrocarbons (asphaltite and kerite). These materials are very dark in the visible and have red-sloped spectra in the visible and near-infrared. They may be comparable in composition and structure to refractory organic solids on the surfaces of primitive outer Solar System objects. We irradiated the samples with 15-400 keV H<sup>+</sup>, N<sup>+</sup>, Ar<sup>++</sup>, and He<sup>+</sup> ions and measured their reflectance spectra in the range of 0.3-2.5 microns before ion implantation and after each irradiation step. The results show that irradiation-induced carbonization gradually neutralizes the spectral slopes of these red organic solids. This implies a similar space weathering trend for the surfaces of airless bodies optically dominated by spectrally red organic components. The reduction of spectral slope was observed in all experiments. Irradiation with 30 keV protons, which transfers energy to the target mostly via electronic (inelastic) collisions, showed lower efficiency than the heavier ions. We found that spectral alteration in our experiments increased with increasing contribution of nuclear versus electronic energy loss. This implies that nuclear (elastic) energy deposition plays an important role in changing the optical properties of irradiated refractory complex hydrocarbon materials. Finally, our results indicated that temperature variations from 40 K to room temperature did not influence the spectral properties of these complex hydrocarbon solids.

Item URL in elib:https://elib.dlr.de/46307/
Document Type:Article
Title:Optical alteration of complex organics induced by ion-irradiation: 1. Laboratory experiments suggest unusual space weathering trend.
Authors:
AuthorsInstitution or Email of AuthorsAuthors ORCID iD
Moroz, L. V.UNSPECIFIEDUNSPECIFIED
Baratta, G.INAF Catania Astrophysical ObservatoryUNSPECIFIED
Strazzulla, G.INAF Catania Astrophysical ObservatoryUNSPECIFIED
Starukhina, L. V.Astronomical Institute, Kharkov UniversityUNSPECIFIED
Dotto, E.INAF Rome Astrophysical ObservatoryUNSPECIFIED
Barucci, M. A.Paris ObservatoryUNSPECIFIED
Arnold, G.UNSPECIFIEDUNSPECIFIED
Distefano, E.INAF Catania Astrophysical ObservatoryUNSPECIFIED
Date:2004
Journal or Publication Title:Icarus: International Journal of Solar System Studies
Refereed publication:Yes
Open Access:No
Gold Open Access:No
In SCOPUS:No
In ISI Web of Science:Yes
Volume:170
Page Range:pp. 214-228
Status:Published
Keywords:Organic chemistry, Radiation chemistry, Spectroscopy, infrared
HGF - Research field:Aeronautics, Space and Transport (old)
HGF - Program:Space (old)
HGF - Program Themes:W - no assignment
DLR - Research area:Space
DLR - Program:W - no assignment
DLR - Research theme (Project):W - no assignment (old)
Location: Berlin-Adlershof
Institutes and Institutions:Optical Information Systems
Deposited By: Moroz, Dr. Liubov
Deposited On:03 Jan 2007
Last Modified:27 Apr 2009 13:21

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