Ion irradiation of CH4-containing icy mixtures

Baratta, G. A.; Domingo, M.; Ferini, G.; Leto, G.; Palumbo, M. E.; Satorre, M. Á.; Strazzulla, G.

doi:10.1016/s0168-583x(02)02010-4

Cited by 30 publications

(32 citation statements)

References 10 publications

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“…Hence, the higher cross-section for disappearance of CO at 40 K is probably due to its desorption and not to a more efficient dissociation of this molecule. The role of temperature in these samples became evident when we considered that the ratio H 2 O:CO increased from 10:1 before irradiation to 40:1 at the end of irradiation at 12 K and to 140:1 at the end of irradiation at 40 K. These spectra are similar to those of the sample prepared and irradiated at 40 K. The irradiation of these mixtures led to the production of several new molecules, mainly CO 2 but also CO, ethane (C 2 H 6 ), formaldehyde (H 2 CO), and methanol (CH 3 OH) (see e.g., Baratta et al 2003). Peak positions and the identification of the bands detected before and after irradiation can be found in Table 5.…”

Section: Resultssupporting

confidence: 65%

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The influence of temperature on the synthesis of molecules on icy grain mantles in dense molecular clouds

Garozzo

Rosa

Kaňuchová

et al. 2011

A&A

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Context. Infrared observations show the presence of icy mantles along the line of sight toward young stellar objects (YSOs), where a temperature gradient is expected and indirectly observed. In this environment, icy mantles are affected by ion and UV irradiation. Laboratory experiments show that molecules are formed after irradiation of icy mixtures. However, most of the experiments done so far have been performed in the temperatures range of 10-20 K. Aims. To extend previous work we irradiated some icy mixtures, namely H 2 O:CO=10:1, H 2 O:CH 4 =4:1, and H 2 O:CO 2 =3:1 at two different temperatures (12 K and 40 or 60 K) to study the effects of temperature on the synthesis of molecules and the decrease in their parent species after ion irradiation. Methods. The experiments were performed in a high-vacuum chamber (P < 10 −7 mbar), where icy samples were irradiated with 30 keV He + ions and analyzed by a FTIR spectrophotometer. Infrared spectra of the samples were recorded after various steps of irradiation. Results. We found that the temperature affects the behavior of the volatile species (i.e., CO and CH 4 ) during irradiation. As a consequence, the production of molecular species is generally more prevalent at 12 K than at either 40 or 60 K, while the decrease in their parent volatile species is faster at high temperature. Conclusions. We conclude that the behavior of each species depends on the value of its sublimation temperature with respect to the temperature of the sample. If this latter is higher than the sublimation temperature of a given species, then the effects of thermal desorption compete with those due to irradiation.

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Section: Resultssupporting

confidence: 65%

“…From other experiments (e.g. Baratta et al 2003), we know that other species (such as C 3 H 8 and C 2 H 4 ) are formed after the irradiation of H 2 O:CH 4 mixtures. However, because of the lower thickness of the samples in the present experiments the bands corresponding to these species are not evident in the spectra.…”

Section: Resultsmentioning

confidence: 91%

The influence of temperature on the synthesis of molecules on icy grain mantles in dense molecular clouds

Garozzo

Rosa

Kaňuchová

et al. 2011

A&A

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“…Furthermore, slight remaining differences between the observed spectra and modeled spectra that included H 2 O ice and CH 4 ice were best explained by the presence of ethane, another hydrocarbon ice, that is a likely by-product of CH 4 irradiation (Baratta et al 2003). The detection of small amounts of CH 4 on Quaoar is not too surprising.…”

Section: Introductionmentioning

confidence: 86%

Composition of KBO (50000) Quaoar

Ore

Barucci

Emery³

et al. 2009

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Aims. The objective of this work is to investigate the physical properties of objects beyond Neptune -the new frontiers of the Solar System -and in particular to study the surface composition of (50 000) Quaoar, a classical Transneptunian (or Kuiper Belt) object. Because of its distance from the Sun, Quaoar is expected to have preserved, to a degree, its original composition. Our goals are to determine to what degree this is true and to shed light on the chemical evolution of this icy body. Methods. We present new near-infrared (3.6 and 4.5 μm) photometric data obtained with the Spitzer Space Telescope. These data complement high resolution, low signal-to-noise spectroscopic and photometric data obtained in the visible and near-infrared (0.4-2.3 μm) at VLT-ESO and provide an excellent set of constraints in the model calculation process. We perform spectral modeling of the entire wavelength range -from 0.3 to 4.5 μm by means of a code based on the Shkuratov radiative transfer formulation of the slab model. We also attempt to determine the temperature of H 2 O ice making use of the crystalline feature at 1.65 μm.Results. We present a model confirming previous results regarding the presence of crystalline H 2 O and CH 4 ice, as well as C 2 H 6 and organic materials, on the surface of this distant icy body. We attempt a measurement of the temperature and find that stronger constraints on the composition are needed to obtain a precise determination. Conclusions. Model fits indicate that N 2 may be a significant component, along with a component that is bright at λ > 3.3 μm, which we suggest at this time could be amorphous H 2 O ice in tiny grains or thin grain coatings. Irradiated crystalline H 2 O could be the source of small-grained amorphous H 2 O ice. The albedo and composition of Quaoar, in particular the presence of N 2 , if confirmed, make this TNO quite similar to Triton and Pluto.

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“…Ethane is an irradiation product (from UV photolysis) of solid ethane (Baratta et al 2003), and is expected to be involatile at ∼40 K. Therefore, once produced by solar irradiation, it should remain at the surface of the object and still be observable. Moore & Hudson (2003) report that the production of C 2 H 6 is more efficient when CH 4 is pure.…”

Section: Search For Daughter Species Of Methane and Ammoniamentioning

confidence: 99%

Methane, ammonia, and their irradiation products at the surface of an intermediate-size KBO?

Delsanti¹,

Merlin²,

Guilbert-Lepoutre³

et al. 2010

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Orcus is an intermediate-size 1000 km-scale Kuiper belt object (KBO) in 3:2 mean-motion resonance with Neptune, in an orbit very similar to that of Pluto. It has a water-ice dominated surface with solar-like visible colors. We present visible and near-infrared photometry and spectroscopy obtained with the Keck 10 m-telescope (optical) and the Gemini 8 m-telescope (near-infrared). We confirm the unambiguous detection of crystalline water ice as well as absorption in the 2.2 μm region. These spectral properties are close to those observed for Pluto's larger satellite Charon, and for Plutino (208996) 2003 AZ 84 . Both in the visible and near-infrared Orcus' spectral properties appear to be homogeneous over time (and probably rotation) at the resolution available. From Hapke radiative transfer models involving intimate mixtures of various ices we find for the first time that ammonium (NH + 4 ) and traces of ethane (C 2 H 6 ), which are most probably solar irradiation products of ammonia and methane, and a mixture of methane and ammonia (diluted or not) are the best candidates to improve the description of the data with respect to a simple water ice mixture (Haumea type surface). The possible more subtle structure of the 2.2 μm band(s) should be investigated thoroughly in the future for Orcus and other intermediate size Plutinos to better understand the methane and ammonia chemistry at work, if any. We investigated the thermal history of Orcus with a new 3D thermal evolution model. Simulations over 4.5×10 9 yr with an input 10% porosity, bulk composition of 23% amorphous water ice and 77% dust (mass fraction), and cold accretion show that even with the action of long-lived radiogenic elements only, Orcus should have a melted core and most probably suffered a cryovolcanic event in its history which brought large amounts of crystalline ice to the surface. The presence of ammonia in the interior would strengthen the melting process. A surface layer of a few hundred meters to a few tens of kilometers of amorphous water ice survives, while most of the remaining volume underneath contains crystalline ice. The crystalline water ice possibly brought to the surface by a past cryovolcanic event should still be detectable after several billion years despite the irradiation effects, as demonstrated by recent laboratory experiments.

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Ion irradiation of CH4-containing icy mixtures

Cited by 30 publications

References 10 publications

The influence of temperature on the synthesis of molecules on icy grain mantles in dense molecular clouds

The influence of temperature on the synthesis of molecules on icy grain mantles in dense molecular clouds

Composition of KBO (50000) Quaoar

Methane, ammonia, and their irradiation products at the surface of an intermediate-size KBO?

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