Photochemical activity of Titan’s low-altitude condensed haze

Gudipati, Murthy S.; Jacovi, Ronen; Couturier-Tamburelli, Isabelle; Lignell, Antti; Allen, Mark

doi:10.1038/ncomms2649

Cited by 50 publications

(52 citation statements)

References 49 publications

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“…5 compared to the residue obtained after C 4 N 2 irradiation and tholins generated by different methods. Our HC 5 N residue spectrum presents common tholin absorption bands (Coll et al 2013;Imanaka et al 2004Imanaka et al , 2012CouturierTamburelli et al 2014a;Gudipati et al 2013). We can observe the presence of intense and broad bands in the νNH stretching area due to the presence of amines functions (∼3250 cm −1 ).…”

Section: Infrared Spectrum Of the Hc 5 N Residuesupporting

confidence: 56%

“…Strong evidence for the nitrile ice feature due to HCN, HC 3 N, and C 4 N 2 exists (Samuelson et al 1997;Anderson et al 2010;Khanna et al 1987;de Kok et al 2014). We have recently shown that in the condensed-phase molecules such as C 4 N 2 can be photochemically polymerized at longer wavelength photons that penetrate through into the lower atmosphere of Titan (Gudipati et al 2013;Couturier-Tamburelli et al 2014a).…”

Section: Introductionmentioning

confidence: 99%

“…In our earlier reports we chose C 4 N 2 (Gudipati et al 2013;Couturier-Tamburelli et al 2014a), because this molecule is known to be present in the solid phase of the low atmosphere (Samuelson et al 1997). Our present study is focused on another molecule of the cyanopolyynes family, HC 5 N, to determine whether molecules with permanent dipole moment (HC 5 N) compare with molecules without dipole moment (C 4 N 2 ) during their photopolymerization process in condensed phase.…”

Section: Introductionmentioning

confidence: 99%

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Simulation of Titan’s atmospheric photochemistry

Couturier-Tamburelli

Piétri

Gudipati

2015

A&A

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We studied the photochemistry of frozen ice of a polar Titan's atmospheric molecule cyanodiacetylene (HC 5 N) to determine the possible contribution of this compound to the lower altitude photochemistry of haze layers found on Titan. We used infrared analysis to examine the residue produced by irradiation of solid HC 5 N at λ > 300 nm. The resulting polymer is orange-brown in color. Based on theoretical analysis and the general tendency of HC 5 N and C 4 N 2 to undergo similar ice photochemistry at longer wavelengths accessible in Titan's lower atmosphere, we conclude that Titan's lower atmosphere is photochemically active in the regions of cloud, ice, and aerosol formation. C 4 N 2 is a symmetric molecule with no net dipole moment whereas, HC 5 N has a large dipole moment of ∼4 D. Consequently, though both these molecules have very similar molecular weight and size, their sublimation temperatures are different, HC 5 N subliming around 170 K compared to 160 K for C 4 N 2 . Based on our studies we conclude that in Titan's atmosphere the cyanoacetylene class of molecules (HCN, HC 3 N, HC 5 N, etc.) would condense first followed by the dicyanoacetylenes (C 2 N 2 , C 4 N 2 , C 6 N 2 , etc.), leading to fractionation of different class of molecules. From the fluxes used in the laboratory and depletion of the original HC 5 N signals, we estimate Titan's haze ice photochemistry involving polar nitriles to be significant and very similar to their non-polar counterparts.

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Section: Infrared Spectrum Of the Hc 5 N Residuesupporting

confidence: 56%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Simulation of Titan’s atmospheric photochemistry

Couturier-Tamburelli

Piétri

Gudipati

2015

A&A

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“…Pure solid state C 2 H 2 has been found on Titan, both on the ground (Lara et al 1996) and as ice particles in the atmosphere (Gudipati et al 2011). In observational studies, it is used as a tracer for warm (100−1000 K) molecular gas (Sonnentrucker et al 2007).…”

Section: Introductionmentioning

confidence: 99%

“…Linear carbon chain radicals have been detected in the surrounding environment of carbon stars (Cernicharo 2004) and are part of the UV haze in Titan's atmosphere (Gudipati et al 2011, and references therein). The gas phase reaction pathways to the formation of carbon chain species have been studied well, which explains the variety of carbon chain species observed in space (Jolly & Bénilan 2008).…”

Section: Introductionmentioning

confidence: 99%

Vacuum ultraviolet photochemistry of solid acetylene: a multispectral approach

Cuylle

Zhao

Strazzulla

et al. 2014

A&A

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Aims. Gas phase acetylene (C 2 H 2 ) and polyynes (H(-C≡C-) m H) are ubiquitous in the interstellar medium. However, astrochemical models systematically underestimate the observed abundances, supporting the idea that enrichment from the solid state takes place. In this laboratory-based study, we investigate the role C 2 H 2 plays in interstellar ice chemistry and we discuss the way its photoproducts may affect gas phase compositions. Methods. C 2 H 2 ice is investigated under vacuum ultraviolet (VUV) irradiation in its pure form as present in the atmosphere of Titan and in a water-dominated ice as present on grain mantles in molecular clouds and on comets. To disentangle the photochemical network, a unique, complementary combination of infrared and ultraviolet-visible (UV-VIS) spectroscopy is used. Results. From the experimental results, it can be concluded that the VUV-induced solid state C 2 H 2 reaction network is dominated by polymerization resulting in the formation of polyynes at least up to C 20 H 2 and larger polyyne-like molecules. At low temperatures, this process takes place very efficiently and suggests low barriers. When extending this reaction scheme to a water-rich environment, the dominant reaction products are CO and CO 2 but the simultaneous detection of polyyne like molecules is evidence that the reactions as observed in pure C 2 H 2 ice persist. Conclusions. From the spectroscopic evidence as presented in this laboratory study, it is concluded that the formation of polyynes upon VUV irradiation of interstellar ices is a process that may contribute to at least part of the observed gas phase enrichment in space.

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Ion and aerosol precursor densities in Titan's ionosphere: A multi‐instrument case study

et al. 2016

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The importance of the heavy ions and dust grains for the chemistry and aerosol formation in Titan's ionosphere has been well established in the recent years of the Cassini mission. In this study we combine independent in situ plasma (Radio Plasma and Wave Science Langmuir Probe (RPWS/LP)) and particle (Cassini Plasma Science Electron Spectrometer, Cassini Plasma Science Ion Beam Spectrometer, and Ion and Neutral Mass Spectrometer) measurements of Titan's ionosphere for selected flybys (T16, T29, T40, and T56) to produce altitude profiles of mean ion masses including heavy ions and develop a Titan‐specific method for detailed analysis of the RPWS/LP measurements (applicable to all flybys) to further constrain ion charge densities and produce the first empirical estimate of the average charge of negative ions and/or dust grains. Our results reveal the presence of an ion‐ion (dusty) plasma below ~1100 km altitude, with charge densities exceeding the primary ionization peak densities by a factor ≥2 in the terminator and nightside ionosphere (ne/ni ≤ 0.1). We suggest that ion‐ion (dusty) plasma may also be present in the dayside ionosphere below 900 km (ne/ni < 0.5 at 1000 km altitude). The average charge of the dust grains (≥1000 amu) is estimated to be between −2.5 and −1.5 elementary charges, increasing toward lower altitudes.

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Photochemical activity of Titan’s low-altitude condensed haze

Cited by 50 publications

References 49 publications

Simulation of Titan’s atmospheric photochemistry

Simulation of Titan’s atmospheric photochemistry

Vacuum ultraviolet photochemistry of solid acetylene: a multispectral approach

Ion and aerosol precursor densities in Titan's ionosphere: A multi‐instrument case study

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