Exposed amorphous water ice on comet 49P/Arend-Rigaux

Sivaraman, Bhalamurugan; Venkataraman, V.; Kalyaan, Anusha; Arora, Siddharth; Ganesh, S.

doi:10.1016/j.asr.2015.10.003

Cited by 5 publications

(4 citation statements)

References 18 publications

(10 reference statements)

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“…That all three comets inspected, Tempel 1, Tempel 2, and Arend-Rigaux, exhibit a 10-µm plateau indicates that its presence is not correlated with the unusually low activities of the larger nuclei (Tempel 2 and Arend-Rigaux). This interpretation is in contrast to that of Sivaraman et al (2015), who conclude a broad depression near 13 µm in the 5-14-µm spectrum of Arend-Rigaux indicates the presence of amorphous water ice.…”

Section: Discussioncontrasting

confidence: 90%

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Mid-infrared spectra of comet nuclei

Kelley

Woodward

Gehrz

et al. 2017

Icarus

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Jovian Trojan D-type asteroids have mid-infrared emissivity features strikingly similar to comet comae, suggesting that they have the same compositions and that the surfaces of the Trojans are highly porous. However, a direct comparison between a comet and asteroid surface has not been possible due to the paucity of spectra of comet nuclei at mid-infrared wavelengths. We present 5-35 {\mu}m thermal emission spectra of comets 10P/Tempel 2, and 49P/Arend-Rigaux observed with the Infrared Spectrograph on the Spitzer Space Telescope. Our analysis suggests the spectra are dominated by the comet nucleus. We fit each spectrum with the near-Earth asteroid thermal model (NEATM) and find sizes in agreement with previous values. However, the NEATM beaming parameters of the nuclei, 0.74 to 0.83, are systematically lower than the Jupiter-family comet population mean of 1.03+/-0.11, derived from 16- and 22-{\mu}m photometry. When the spectra are normalized by the NEATM model, a weak 10-{\mu}m silicate plateau is evident, with a shape similar to those seen in mid-infrared spectra of D-type asteroids. We compare, in detail, these comet nucleus emission features to those seen in spectra of the Jovian Trojan D-types (624) Hektor, (911) Agamemnon, and (1172) Aneas, as well as those seen in the spectra of seven comet comae. The comet comae present silicate features with two distinct shapes, either trapezoidal, or more rounded. The surfaces of Tempel 2, Arend-Rigaux, and Hektor best agree with the comae that present trapezoidal features. An emissivity minimum at 15 {\mu}m, present in the spectra of Tempel 2, Arend-Rigaux, Hektor, and Agamemnon, is also described, the origin of which remains unidentified. The compositional similarity between D-type asteroids and comets is discussed, and our data supports the hypothesis that they have similar origins in the early Solar System.Comment: Abridged abstract; 46 pages, 10 figures; Author's accepted manuscript with revised acknowledgement

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Section: Discussioncontrasting

confidence: 90%

“…5). Sivaraman et al (2015) examined Arend-Rigaux's 5-14 µm spectrum based on the same data set. They identified a curvature in the spectrum near 12-13 µm and suggested this was an absorption feature due to amorphous water ice on the surface.…”

Section: Spectroscopymentioning

confidence: 99%

Mid-infrared spectra of comet nuclei

Kelley

Woodward

Gehrz

et al. 2017

Icarus

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“…where IE denotes the ionization energy, and IE(1) < IE (2). The final products are strongly dependent on the electronic states and the ionization energy.…”

Section: Resultsmentioning

confidence: 99%

“…The strong light excites and ionizes the electronic states of the molecules. The CO 2 and H 2 O molecule covering the surface of comets − will cause various reactions after being ionized. The ionized H 2 O + reacts easily with the surrounding molecule (M), and proton transfer (PT) takes place: H 2 O + + M → M–H + + OH.…”

Section: Introductionmentioning

confidence: 99%

Activation of CO₂ in Photoirradiated CO₂–H₂O Clusters: Direct Ab Initio Molecular Dynamics (MD) Study

Tachikawa

2019

J. Phys. Chem. A

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Carbon dioxide (CO2) is one of the stable and inactive molecules that contribute to greenhouse gases. The development of new reactions of CO2 activation, chemical fixation, and conversion is a very important issue. In this report, the reactions of CO2–H2O binary clusters were investigated using a direct ab initio molecular dynamics (AIMD) method to find a new reaction of CO2 activation. Clusters composed of carbon dioxide and water molecules, CO2(H2O) n (n = 2–5), were utilized as a model of the binary cluster. The reaction dynamics of [CO2(H2O) n ]+ following the ionization of parent neutral clusters were also investigated. Two electronic states of [CO2(H2O) n ]+ were examined for direct AIMD surfaces: CO2[(H2O) n ]+ (ground state) and (CO2)+(H2O) n (excited charge transfer (CT) state). After the ionization of the clusters, a proton-transfer (PT) reaction occurred within the (H2O) n + moiety at the ground state, whereas the reactive HCO3 radical was formed at the CT state for OH addition to CO2 +: CO2 +(H2O) n → HCO3 + H+(H2O) n−1. The mechanisms of the PT process and the HCO3 radical formation were discussed based on the theoretical results.

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