Ion Irradiation of Frozen Methanol, Methane, and Benzene: Linking to the Colors of Centaurs and Trans‐Neptunian Objects

Brunetto, R.; Barucci, M. A.; Dotto, E.; Strazzulla, G.

doi:10.1086/503359

Cited by 130 publications

(122 citation statements)

References 26 publications

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“…Investigated materials include carbon-based species such as frozen hydrocarbons, present on the outer Solar System objects and interstellar dust grains (Brunetto et al 2006a), red bitumens (asphaltite and kerite, materials which are the most similar to the less evolved organic matter of trans-neptunian Data table is only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/517/A60 objects (TNOs) and comets) (Moroz et al 2004), and materials typical for main-belt asteroids such as different kinds of silicates (Brunetto & Strazzulla 2005;Brunetto et al 2006b;Sasaki et al 2001;Strazzulla et al 2005;Loeffler et al 2009Loeffler et al , 2008. Up to now, the effects of space weathering have not yet been studied on organic materials of low volatility.…”

Section: Introductionmentioning

confidence: 99%

Space weathering of asteroidal surfaces

Kaňuchová

Baratta²,

Garozzo³

et al. 2010

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Context. The surfaces of airless bodies in the Solar System are continuously altered by the bombardment of micrometeoroids and irradiation by solar wind, flares, and cosmic particles. Major effects of this process -space weathering -are darkening and "reddening" of the spectra of surface materials, as well as a "degrading" of absorption features. Aims. We studied the changes induced by energetic ion irradiation in the ultraviolet-visual-near-infrared (UV-Vis-NIR) (0.2-0.98 μm) reflectance spectra of targets selected to mimic the surfaces of airless bodies in the inner Solar System. Our chosen targets are olivine pellets, pure or covered by an organic polymer (polystyrene), which is transparent before irradiation. Polystyrene is used as a template for organic matter of low volatility that can be present on asteroidal surfaces. Moreover we measured the changes induced by ion irradiation in the absorption coefficient of the polymer. The purpose was to have a tool to better compare laboratory with observed spectra and distinguish between planetary objects with pure silicate surfaces and those whose surface is covered by organic matter exposed to cosmic ion bombardment. Methods. The samples were irradiated in vacuum, at room temperature, with 200 keV protons or 200-400 keV argon ions. Before, during, and after irradiation diffuse reflectance spectra were acquired. Polystyrene films were also deposited on quartz substrates and irradiated while transmittance spectra were recorded. Results. We measured the variations of the absorption coefficient of polystyrene as a function of ion fluence. We showed that after ion irradiation the diffuse reflectance spectra of the samples covered by organics exhibit a much more significant variation than those of pure silicates. The spectra of targets made of olivine plus polystyrene can be fitted by using the measured absorption coefficient of polystyrene. Conclusions. The results obtained for pure olivine extend to the UV the spectral range of previous experiments. The data concerning the absorption coefficient of polystyrene are available on our web site (http://web.ct.astro.it/weblab/dbindex.html) and can be used to compare laboratory with astronomical spectra. This will possibly allow us to obtain information about organic matter on the surface of a given object, as well as on the relevance of the exposure to cosmic ions (space weathering).

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Section: Introductionmentioning

confidence: 99%

Space weathering of asteroidal surfaces

Kaňuchová

Baratta²,

Garozzo³

et al. 2010

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“…In contrast to comets that display methanol that comes from the protected interior of the nucleus, methanol on the surface of TNOs and Centaurs is not expected to survive a long time (see effects on different mixtures containing methanol in Gerakines et al 1996). Brunetto et al (2006) performed irradiation of a 1 micrometer CH 3 OH sample at different dose levels. With a dose equal to, or even lower than, to 44 eV/16 amu, the authors obtained a red crust in which the absorption features in the nIR almost completely disappeared.…”

Section: Discussionmentioning

confidence: 99%

“…Most of them possess no atmosphere and have chemically evolved surfaces. The smaller bodies have been depleted of volatile species and ices at different levels on the surface (Brunetto et al 2006). Investigating their surface by spectroscopy is a tool for constraining the chemical properties and the evolution processes that occurr in the solar system.…”

Section: Introductionmentioning

confidence: 99%

Methanol ice on the surface of minor bodies in the solar system

Merlin¹,

Quirico²,

Barucci³

et al. 2012

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Aims. Spectral analyses of trans-Neptunan objects (TNOs) and of the linked Centaurs, which are supposed to be among the most primitive minor bodies in the solar system, reveal some chemical and physical properties of their surface. To determine the surface composition of these objects and their surface evolution is essential for gaining clues on the conditions under which the solar system has been formed. Methods. Chemical composition and physical properties of the surface of three objects have been constrained by computing the depth of the absorption features of the spectra in the near-infrared, running spectral models based on radiative transfer theory in the [0.4−2.3] μm range, and analyzing new laboratory measurements of the spectral behavior of thin samples of H 2 O-CH 3 OH mixtures. Results. Our investigations allow us to confirm the presence of CH 3 OH ice on the surface of the Centaur (5145) Pholus and the resonant (55638) TNO 2002 VE 95 . It may also possibly be found on the classical TNO (120348) 2004 TY 364 . Our laboratory experiments indicate that the behavior of the methanol and water ice absorption bands is dependent on the ambient temperature and the dilution level of the mixture. These results also suggest that methanol may be diluted in water ice on the surface of the Centaur Pholus. Conclusions. Formation and destruction processes of methanol suggest that a part (at least) of the surface of these objects is younger than the solar system age. If confirmed, this shows that primordial ices could still be detected on the surface of objects that are submitted to irradiation and rejuvenation processes.

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“…Among these processes UV irradiation and cosmic ion irradiation play an important role in the life-cycle of interstellar dust (Mennella et al 2003), in the production of complex organics in the presolar nebula (Muñoz-Caro et al 2006) as well as on the surface of TNOs and other minor bodies (Brunetto et al 2006), and in the alteration of pre-existing carbon materials (Moroz et al 2004;Baratta et al 2008). Many studies point out that the early Sun was much more active than today, passing through an active T Tauri phase before reaching the main sequence (e.g., Feigelson & Montmerle 1999); such strong particle and photon radiation could have had major influences on processing material during the planetary accretion phase, and more specifically on the carbon chemistry.…”

Section: Laboratory Studies Of Refractory Carbonaceous Materialsmentioning

confidence: 99%

“…ices, initially red solids, and polymer-like initially transparent solids), have been irradiated. They are: frozen (16 K) methane (CH 4 ) (Brunetto et al 2006), asphaltite (a natural bitumen) (Moroz et al 2004), and a film of polystyrene deposited on a silicate (olivine) (Kanuchova et al 2010).…”

Section: Ion Irradiation and The Colors Of C-rich Materialsmentioning

confidence: 99%

Organic materials in planetary and protoplanetary systems: nature or nurture?

Ore

Fulchignoni

Cruikshank

et al. 2011

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Aims. The objective of this work is to summarize the discussion of a workshop aimed at investigating the properties, origins, and evolution of the materials that are responsible for the red coloration of the small objects in the outer parts of the solar system. Because of limitations or inconsistencies in the observations and, until recently, the limited availability of laboratory data, there are still many questions on the subject. Our goal is to approach two of the main questions in a systematic way: -Is coloring an original signature of materials that are presolar in origin ("nature") or stems from post-formational chemical alteration, or weathering ("nurture")? -What is the chemical signature of the material that causes spectra to be sloped towards the red in the visible? We examine evidence available both from the laboratory and from observations sampling different parts of the solar system and circumstellar regions (disks). Methods. We present a compilation of brief summaries gathered during the workshop and describe the evidence towards a primordial vs. evolutionary origin for the material that reddens the small objects in the outer parts of our, as well as in other, planetary systems. We proceed by first summarizing laboratory results followed by observational data collected at various distances from the Sun. Results. While laboratory experiments show clear evidence of irradiation effects, particularly from ion bombardment, the first obstacle often resides in the ability to unequivocally identify the organic material in the observations. The lack of extended spectral data of good quality and resolution is at the base of this problem. Furthermore, that both mechanisms, weathering and presolar, act on the icy materials in a spectroscopically indistinguishable way makes our goal of defining the impact of each mechanism challenging. Conclusions. Through a review of some of the workshop presentations and discussions, encompassing laboratory experiments as well as observational data, we infer that both "nature" and "nurture" are instrumental in the coloration of small objects in the outer parts Article published by EDP Sciences A98, page 1 of 14 A&A 533, A98 (2011) of the solar system. While in the case of some observations it is clear that the organic reddening material originated before the solar nebula (i.e. presolar grains found in meteorites), for many other cases pointers are not as clear and indicate a concurrence of both processes.

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Ion Irradiation of Frozen Methanol, Methane, and Benzene: Linking to the Colors of Centaurs and Trans‐Neptunian Objects

Cited by 130 publications

References 26 publications

Space weathering of asteroidal surfaces

Space weathering of asteroidal surfaces

Methanol ice on the surface of minor bodies in the solar system

Organic materials in planetary and protoplanetary systems: nature or nurture?

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