Complex Refractive Index of Titan's Aerosol Analogues in the 200–900 nm Domain

Ramírez, Sandra I.

doi:10.1006/icar.2001.6783

Cited by 84 publications

(44 citation statements)

References 37 publications

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“…McKay (1 996) showed that optical properties vary with the tholins produced from different initial CH4/N2 ratios by comparing their transmittances in the ultraviolet-visible (W/Vis) spectral ranges. Ramirez et al (2002) measured the optical properties of tholin formed from a CfiN2 gas mixture (2/98) at about 1 hPa, and found a ten times smaller value of k (the imaginary component of the complex refiactive index) in the W N i s ranges than those measured by Khare et al (1984). This difference reveals that the properties of Recently, hanaka (2004) and Imanaka et al (2004) systematically investigated a range of Titan tholins produced under various pressures in cold plasma.…”

Section: New Research On Tholinsmentioning

confidence: 80%

“…Although polycyclic aromatic hydrocarbons and some functional groups were suggested in Titan tholin (Khare et al, 1984;Sagan et al, 1993), other details of the chemical structure remain unclear. Many laboratory simulations have been conducted to investigate the optical and chemical properties of tholins (McDonald et al 1994;McKay 1996;Coll et al 1999, Ramirez et al 2002. McDonald et ai.…”

Section: New Research On Tholinsmentioning

confidence: 99%

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Tholins as coloring agents on outer Solar System bodies

Cruikshank¹,

Imanaka²,

Ore³

2005

Advances in Space Research

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The red colors of many solid bodies in outer Solar System may be caused by tholins, which are refiactory organic complexes, incorporated in their surface materials. Tholins synthesized in the laboratory are shown to match the colors of these bodies when their optical properties are used in rigorous scattering models. We review recent successes in modeling the spectra of icy outer Solar System bodies with tholins as the coloring agents. New work on the systematic laboratory synthesis and analysis of tholins made by cold plasma discharge in mixtures of gaseous CH& shows that the composition of the tholin depends strongly on the pressure in the reaction chamber, and only weakly on the mixing fraction of C& relative to Nz. In tholins made at high pressure (e.g., 23 hPa) the abundance of aliphatic hydrocarbons is greater and the abundance of aromatic hydrocarbons is less than in tholins made at low pressure (e.g., 0.13 ma). Tholins made at low deposition pressures show a greater abundance of N-H bonds.

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Section: New Research On Tholinsmentioning

confidence: 80%

Section: New Research On Tholinsmentioning

confidence: 99%

Tholins as coloring agents on outer Solar System bodies

Cruikshank¹,

Imanaka²,

Ore³

2005

Advances in Space Research

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“…The optical properties (i.e. complex indices of refraction as a function of wavelength) were compiled in order of decreasing condensation temperature from 1316 to 90 K for MgSiO3, Fe-poor Mg2SiO4, Na2S, MnS, KCl, and Titan tholin with all condensates at pressures 10 −3 bar (Egan & Hilgeman 1975;Zeidler et al 2011;Khachai et al 2009;Huffman & Wild 1967;Palik 1998;Khare et al 1984;Ramirez et al 2002). As in Sing et al (2013) cross-sections as a function of wavelength were computed with Mie theory which were then used to compute the transmission spectra using the expression for the planetary altitude derived in Lecavelier Des Etangs et al (2008a).…”

Section: Mie Scattering Dustmentioning

confidence: 99%

HST hot-Jupiter transmission spectral survey: haze in the atmosphere of WASP-6b

Nikolov

Sing

Burrows

et al. 2014

Monthly Notices of the Royal Astronomical Society

152

142

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We report Hubble Space Telescope (HST) optical to near-infrared transmission spectroscopy of the hot Jupiter WASP-6b, measured with the Space Telescope Imaging Spectrograph (STIS) and Spitzer's InfraRed Array Camera (IRAC). The resulting spectrum covers the range 0.29 − 4.5 µm. We find evidence for modest stellar activity of WASP-6 and take it into account in the transmission spectrum. The overall main characteristic of the spectrum is an increasing radius as a function of decreasing wavelength corresponding to a change of ∆(R p /R * ) = 0.0071 from 0.33 to 4.5 µm. The spectrum suggests an effective extinction cross-section with a power law of index consistent with Rayleigh scattering, with temperatures of 973 ± 144 K at the planetary terminator. We compare the transmission spectrum with hot-Jupiter atmospheric models including condensate-free and aerosol-dominated models incorporating Mie theory. While none of the clear-atmosphere models is found to be in good agreement with the data, we find that the complete spectrum can be described by models that include significant opacity from aerosols including Fe-poor Mg 2 SiO 4 , MgSiO 3 , KCl and Na 2 S dust condensates. WASP-6b is the second planet after HD 189733b which has equilibrium temperatures near ∼ 1200 K and shows prominent atmospheric scattering in the optical.

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“…At the same time, we do not expect trace amounts of O 3 in the H 2 O ice of Rhea (and Dione) to have a significant effect on the appearance of the spectra beyond the ultraviolet, apart from a possible weak band near 0.6 µm, based on the gas phase O 3 spectrum. Ramirez et al (2002) have published complex refractive indices (0.2-0.9 µm) for a new tholin produced by cold plasma discharge in a gas that simulates Titan's atmosphere. The values of the imaginary refractive index, k in the region of our modeling (0.3-0.9 µm) are less than those of the Titan tholin of Khare et al (1984) by a factor ranging from about 5 to 15, and the shape of the absorption spectrum is different.…”

Section: The Role Of Tholin In the Modelsmentioning

confidence: 99%

A spectroscopic study of the surfaces of Saturn's large satellites: HO ice, tholins, and minor constituents

Cruikshank¹,

Owen²,

Ore³

et al. 2005

Icarus

100

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We present spectra of Saturn's icy satellites Mimas, Enceladus, Tethys, Dione, Rhea, and Hyperion, 1.0-2.5 µm, with data extending to shorter (Mimas and Enceladus) and longer (Rhea and Dione) wavelengths for certain objects. The spectral resolution (R = λ/ λ) of the data shown here is in the range 800-1000, depending on the specific instrument and configuration used; this is higher than the resolution (R = 225 at 3 µm) afforded by the Visual-Infrared Mapping Spectrometer on the Cassini spacecraft. All of the spectra are dominated by water ice absorption bands and no other features are clearly identified. Spectra of all of these satellites show the characteristic signature of hexagonal H 2 O ice at 1.65 µm. We model the leading hemisphere of Rhea in the wavelength range 0.3-3.6 µm with the Hapke and the Shkuratov radiative transfer codes and discuss the relative merits of the two approaches to fitting the spectrum. In calculations with both codes, the only components used are H 2 O ice, which is the dominant constituent, and a small amount of tholin (Ice Tholin II). Tholin in small quantities (few percent, depending on the mixing mechanism) appears to be an essential component to give the basic red color of the satellite in the region 0.3-1.0 µm. The quantity and mode of mixing of tholin that can produce the intense coloration of Rhea and other icy satellites has bearing on its likely presence in many other icy bodies of the outer Solar System, both of high and low geometric albedos. Using the modeling codes, we also establish detection limits for the ices of CO 2 (a few weight percent, depending on particle size and mixing), CH 4 (same), and NH 4 OH (0.5 weight percent) in our globally averaged spectra of Rhea's leading hemisphere. New laboratory spectral data for NH 4 OH are presented for the purpose of detection on icy bodies. These limits for CO 2 , CH 4 , and NH 4 OH on Rhea are also applicable to the other icy satellites for which spectra are presented here. The reflectance spectrum of Hyperion shows evidence for a broad, unidentified absorption band centered at 1.75 µm.

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Complex Refractive Index of Titan's Aerosol Analogues in the 200–900 nm Domain

Cited by 84 publications

References 37 publications

Tholins as coloring agents on outer Solar System bodies

Tholins as coloring agents on outer Solar System bodies

HST hot-Jupiter transmission spectral survey: haze in the atmosphere of WASP-6b

A spectroscopic study of the surfaces of Saturn's large satellites: HO ice, tholins, and minor constituents

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