PAHs in Comets: An Overview

Li, Aigen

doi:10.1007/978-3-540-76959-0_21

Cited by 25 publications

(12 citation statements)

References 81 publications

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“…We should point out that, despite the general view now is that PAHs widely exist in the interstellar space, producing 3.3, 6.2, 7.7, 8.6 and 11.3 μm infrared emission bands, except phenanthrene, but pyrene and perylene have been found in the cometary dust and meteorites (see Li [109] ), not even a single specific PAH molecule has been observed in the interstellar space (see Draine et al [110] ).…”

Section: Polycyclic Aromatic Hydrocarbons (Pahs)mentioning

confidence: 97%

Diffuse interstellar absorption bands

Xiang

Liang

2009

Sci. China Ser. G-Phys. Mech. Astron.

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The diffuse interstellar bands (DIBs) are a large number of absorption bands that are superposed on the interstellar extinction curve and are of interstellar origin. Since the discovery of the first two DIBs in the 1920s, the exact nature of DIBs still remains unclear. This article reviews the history of the detections of DIBs in the Milky Way and external galaxies, the major observational characteristics of DIBs, the correlations or anti-correlations among DIBs or between DIBs and other interstellar features (e.g. the prominent 2175 Angstrom extinction bump and the far-ultraviolet extinction rise), and the proposed candidate carriers. Whether they are also present in circumstellar environments is also discussed.astrophysics, interstellar matter, interstellar extinction, diffuse interstellar band, circumstellar environment

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Section: Polycyclic Aromatic Hydrocarbons (Pahs)mentioning

confidence: 97%

Diffuse interstellar absorption bands

Xiang

Liang

2009

Sci. China Ser. G-Phys. Mech. Astron.

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“…PAHs are often detected around more evolved stars; for example, PAHs have been detected in almost 60% of disks surrounding intermediate mass stars, like Herbig Ae/Be, while only 8% of those surrounding T Tauri stars. , The infrared spectra of star and planet formation regions often show the presence of PAH emission features. This PAH emission originates from either the disk or the envelope in regions with radii of 10–60 AU. ,− PAHs have also been detected in carbonaceous chondrites, − asteroids, , interplanetary dust particles, comets, , and tentatively identified in the planetary satellites Iapetus and Phoebe . The fact that they have been detected ubiquitously in space is why it is essential to study and understand the physics and chemistry involved in their life cycle.…”

Section: Introductionmentioning

confidence: 99%

Polycyclic Aromatic Hydrocarbons and Dust Particle Surface Interactions: Catalytic Hydrogenation of Polycyclic Aromatic Hydrocarbon Molecules under Vacuum Conditions

Cruz-Díaz

Ricca

Mattioda

2020

ACS Earth Space Chem.

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This work reports experiments on the catalytic interaction occurring between polycyclic aromatic hydrocarbon (PAH) molecules and TiO 2 dust grain surfaces under vacuum conditions. The investigation sheds light on the potential catalytic pathways that TiO 2 dust surfaces provide in the hydrogenation of PAH molecules and the chemistry that can be driven by PAH-dust interactions under vacuum conditions. Naphthalene, anthracene, and coronene were chosen as the PAH molecules, while titanium dioxide was selected as the dust analog. PAH samples and dust analog mixtures were studied under vacuum for 24 h while monitored via diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The acquired spectra show that PAH molecules are hydrogenated when in contact with TiO 2 dust particles without the need for external energy or hydrogen sources. Our results suggest that linear PAHs undergo a similar hydrogenation process where the dominant species are fully hydrogenated PAHs. For larger condensed PAHs, the hydrogenation process yields partially hydrogenated molecules. Fully hydrogenated species can be identified by a band around 2960 cm −1 , while partially hydrogenated species produce a band around 2825 cm −1 . In the case of the production of hydrogenated species, our results suggest that the smaller the PAH, the faster the hydrogenation rate.

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“…Therefore, PAHs should be present, or should have been present in the past, on all planetary bodies in the solar system (Dullemond et al, 2007). PAHs have been detected on the surfaces of Saturnian icy moons and comets (Cruikshank et al, 2008(Cruikshank et al, , 2014Li, 2008;Lopez-Puertas et al, 2013) and have been measured in other carbonaceous chondrites meteorites at the level of a few ppm (Becker et al, 1997).…”

Section: Polycyclic Aromatic Hydrocarbonsmentioning

confidence: 99%

The Detectability Limit of Organic Molecules Within Mars South Polar Laboratory Analogs

et al. 2021

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Our neighboring planet, Mars, has increasingly been the target of scientific exploration and of particular interest are its geological history, current environmental conditions, and perhaps most importantly, its potential as a host for extraterrestrial life (Fairén et al., 2010). The polar caps of Mars have more recently emerged as an area of scientific interest due to their abundance of water ice and their dynamic nature, especially with the discovery of a possible stable body of liquid water beneath the Martian South Pole (Orosei et al., 2018). The Martian North and South Pole have permanent ice caps that expand throughout their respective winters, and maintain residual caps in the summer. The North Polar Cap is composed almost entirely of water ice, while the longer, colder winter in the higher altitude southern hemisphere means that the central part Abstract A series of laboratory experiments was carried out in order to generate a diagnostic spectrum for polycyclic aromatic hydrocarbons (PAHs) of astrobiological interest in the context of the Martian South Polar Residual Cap (SPRC), to establish PAH spectral features more easily detectable in CO 2 ice (mixed with small amounts of H 2 O ice) than the previously reported absorption feature at 3.29 µm in order to constrain their detectability limit. There is currently no existing literature on PAH detection within SPRC features, making this work novel and impactful given the recent discovery of a possible subglacial lake beneath the Martian South Pole. Although they have been detected in Martian meteorites, PAHs have not been detected yet on Mars, possibly due to the deleterious effects of ultraviolet radiation on the surface of the planet. SPRC features may provide protection to fragile molecules, and this work seeks to provide laboratory data to improve interpretation of orbital remote sensing spectroscopic imaging data. We also ascertain the effect of CO 2 ice sublimation on organic spectra, as well as provide PAH reference spectra in mixtures relevant to Mars. A detectability limit of ∼0.04% has been recorded for observing PAHs in CO 2 ice using laboratory instrument parameters emulating those of the Compact Reconnaissance Imaging Spectrometer for Mars, with new spectral slope features revealed between 0.7 and 1.1 µm, and absorption features at 1.14 and most sensitively, at 1.685 µm. Mars regolith analog mixed with a concentration of 1.5% PAHs resulted in no discernible organic spectral features. These detectability limits measured in the laboratory are discussed and extrapolated to the effective conditions on the Mars South Polar Cap in terms of dust and water ice abundance and CO 2 ice grain size for both the main perennial cap and the H 2 O ice-dust sublimation lag deposit.Plain Language Summary Carbon molecule chains, or organics, are considered important in the search for life, as all life that we know of on Earth is made from carbon. A particular type of organic, PAHs, that are really common on Earth and throughout space, have never been found on Mars ...

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PAHs in Comets: An Overview

Cited by 25 publications

References 81 publications

Diffuse interstellar absorption bands

Diffuse interstellar absorption bands

Polycyclic Aromatic Hydrocarbons and Dust Particle Surface Interactions: Catalytic Hydrogenation of Polycyclic Aromatic Hydrocarbon Molecules under Vacuum Conditions

The Detectability Limit of Organic Molecules Within Mars South Polar Laboratory Analogs

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