Ion chemistry and N-containing molecules in Titan's upper atmosphere

V. Vuitton, Roger Yelle, M. J. McEwan

Research output: Contribution to journalArticle

263 Citations (Scopus)

Abstract

High-energy photons, electrons, and ions initiate ion-neutral chemistry in Titan's upper atmosphere by ionizing the major neutral species (nitrogen and methane). The Ion and Neutral Mass Spectrometer (INMS) onboard the Cassini spacecraft performed the first composition measurements of Titan's ionosphere. INMS revealed that Titan has the most compositionally complex ionosphere in the Solar System, with roughly 50 ions at or above the detection threshold. Modeling of the ionospheric composition constrains the density of minor neutral constituents, most of which cannot be measured with any other technique. The species identified with this approach include the most complex molecules identified so far on Titan. This confirms the long-thought idea that a very rich chemistry is actually taking place in this atmosphere. However, it appears that much of the interesting chemistry occurs in the upper atmosphere rather than at lower altitudes. The species observed by INMS are probably the first intermediates in the formation of even larger molecules. As a consequence, they affect the composition of the bulk atmosphere, the composition and optical properties of the aerosols and the flux of condensable material to the surface. In this paper, we discuss the production and loss reactions for the ions and how this affects the neutral densities. We compare our results to neutral densities measured in the stratosphere by other instruments, to production yields obtained in laboratory experiments simulating Titan's chemistry and to predictions of photochemical models. We suggest neutral formation mechanisms and highlight needs for new experimental and theoretical data.

Original languageEnglish (US)
Pages (from-to)722-742
Number of pages21
JournalIcarus
Volume191
Issue number2
DOIs
StatePublished - Nov 15 2007

Fingerprint

Titan
upper atmosphere
chemistry
ion
molecules
ions
mass spectrometers
spectrometer
ionospheres
ionospheric composition
ionosphere
atmospheres
atmosphere
low altitude
formation mechanism
stratosphere
solar system
optical property
aerosols
spacecraft

Keywords

  • Atmospheres
  • composition
  • Ionospheres
  • Organic chemistry
  • Titan

ASJC Scopus subject areas

  • Space and Planetary Science
  • Astronomy and Astrophysics

Cite this

Ion chemistry and N-containing molecules in Titan's upper atmosphere. / Vuitton, V.; Yelle, Roger; McEwan, M. J.

In: Icarus, Vol. 191, No. 2, 15.11.2007, p. 722-742.

Research output: Contribution to journalArticle

Vuitton, V. ; Yelle, Roger ; McEwan, M. J. / Ion chemistry and N-containing molecules in Titan's upper atmosphere. In: Icarus. 2007 ; Vol. 191, No. 2. pp. 722-742.
@article{fb655919c23648a5b4915d54d4aa1a85,
title = "Ion chemistry and N-containing molecules in Titan's upper atmosphere",
abstract = "High-energy photons, electrons, and ions initiate ion-neutral chemistry in Titan's upper atmosphere by ionizing the major neutral species (nitrogen and methane). The Ion and Neutral Mass Spectrometer (INMS) onboard the Cassini spacecraft performed the first composition measurements of Titan's ionosphere. INMS revealed that Titan has the most compositionally complex ionosphere in the Solar System, with roughly 50 ions at or above the detection threshold. Modeling of the ionospheric composition constrains the density of minor neutral constituents, most of which cannot be measured with any other technique. The species identified with this approach include the most complex molecules identified so far on Titan. This confirms the long-thought idea that a very rich chemistry is actually taking place in this atmosphere. However, it appears that much of the interesting chemistry occurs in the upper atmosphere rather than at lower altitudes. The species observed by INMS are probably the first intermediates in the formation of even larger molecules. As a consequence, they affect the composition of the bulk atmosphere, the composition and optical properties of the aerosols and the flux of condensable material to the surface. In this paper, we discuss the production and loss reactions for the ions and how this affects the neutral densities. We compare our results to neutral densities measured in the stratosphere by other instruments, to production yields obtained in laboratory experiments simulating Titan's chemistry and to predictions of photochemical models. We suggest neutral formation mechanisms and highlight needs for new experimental and theoretical data.",
keywords = "Atmospheres, composition, Ionospheres, Organic chemistry, Titan",
author = "V. Vuitton and Roger Yelle and McEwan, {M. J.}",
year = "2007",
month = "11",
day = "15",
doi = "10.1016/j.icarus.2007.06.023",
language = "English (US)",
volume = "191",
pages = "722--742",
journal = "Icarus",
issn = "0019-1035",
publisher = "Academic Press Inc.",
number = "2",

}

TY - JOUR

T1 - Ion chemistry and N-containing molecules in Titan's upper atmosphere

AU - Vuitton, V.

AU - Yelle, Roger

AU - McEwan, M. J.

PY - 2007/11/15

Y1 - 2007/11/15

N2 - High-energy photons, electrons, and ions initiate ion-neutral chemistry in Titan's upper atmosphere by ionizing the major neutral species (nitrogen and methane). The Ion and Neutral Mass Spectrometer (INMS) onboard the Cassini spacecraft performed the first composition measurements of Titan's ionosphere. INMS revealed that Titan has the most compositionally complex ionosphere in the Solar System, with roughly 50 ions at or above the detection threshold. Modeling of the ionospheric composition constrains the density of minor neutral constituents, most of which cannot be measured with any other technique. The species identified with this approach include the most complex molecules identified so far on Titan. This confirms the long-thought idea that a very rich chemistry is actually taking place in this atmosphere. However, it appears that much of the interesting chemistry occurs in the upper atmosphere rather than at lower altitudes. The species observed by INMS are probably the first intermediates in the formation of even larger molecules. As a consequence, they affect the composition of the bulk atmosphere, the composition and optical properties of the aerosols and the flux of condensable material to the surface. In this paper, we discuss the production and loss reactions for the ions and how this affects the neutral densities. We compare our results to neutral densities measured in the stratosphere by other instruments, to production yields obtained in laboratory experiments simulating Titan's chemistry and to predictions of photochemical models. We suggest neutral formation mechanisms and highlight needs for new experimental and theoretical data.

AB - High-energy photons, electrons, and ions initiate ion-neutral chemistry in Titan's upper atmosphere by ionizing the major neutral species (nitrogen and methane). The Ion and Neutral Mass Spectrometer (INMS) onboard the Cassini spacecraft performed the first composition measurements of Titan's ionosphere. INMS revealed that Titan has the most compositionally complex ionosphere in the Solar System, with roughly 50 ions at or above the detection threshold. Modeling of the ionospheric composition constrains the density of minor neutral constituents, most of which cannot be measured with any other technique. The species identified with this approach include the most complex molecules identified so far on Titan. This confirms the long-thought idea that a very rich chemistry is actually taking place in this atmosphere. However, it appears that much of the interesting chemistry occurs in the upper atmosphere rather than at lower altitudes. The species observed by INMS are probably the first intermediates in the formation of even larger molecules. As a consequence, they affect the composition of the bulk atmosphere, the composition and optical properties of the aerosols and the flux of condensable material to the surface. In this paper, we discuss the production and loss reactions for the ions and how this affects the neutral densities. We compare our results to neutral densities measured in the stratosphere by other instruments, to production yields obtained in laboratory experiments simulating Titan's chemistry and to predictions of photochemical models. We suggest neutral formation mechanisms and highlight needs for new experimental and theoretical data.

KW - Atmospheres

KW - composition

KW - Ionospheres

KW - Organic chemistry

KW - Titan

UR - http://www.scopus.com/inward/record.url?scp=35448961955&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=35448961955&partnerID=8YFLogxK

U2 - 10.1016/j.icarus.2007.06.023

DO - 10.1016/j.icarus.2007.06.023

M3 - Article

AN - SCOPUS:35448961955

VL - 191

SP - 722

EP - 742

JO - Icarus

JF - Icarus

SN - 0019-1035

IS - 2

ER -