The vertical structure of Titan's upper atmosphere from Cassini Ion Neutral Mass Spectrometer measurements

Roger Yelle, N. Borggren, V. de la Haye, W. T. Kasprzak, H. B. Niemann, I. Müller-Wodarg, J. H. Waite

Research output: Contribution to journalArticle

77 Citations (Scopus)

Abstract

Data acquired by the Ion Neutral Mass Spectrometer (INMS) on the Cassini spacecraft during its close encounter with Titan on 26 October 2004 reveal the structure of its upper atmosphere. Altitude profiles of N2, CH4, and H2, inferred from INMS measurements, determine the temperature, vertical mixing rate, and escape flux from the upper atmosphere. The mean atmospheric temperature in the region sampled by the INMS is 149 ± 3   K, where the variance is a consequence of local time variations in temperature. The CH4 mole fraction at 1174 km is 2.71 ± 0.1 %. The effects of diffusive separation are clearly seen in the data that we interpret as an eddy diffusion coefficient of 4-3+4 × 109   cm2 s-1, that, along with the measured CH4 mole fraction, implies a mole fraction in the stratosphere of 2.2 ± 0.2 %. The H2 distribution is affected primarily by upward flow and atmospheric escape. The H2 mole fraction at 1200 km is 4 ± 1 × 10-3 and analysis of the altitude profile indicates an upward flux of 1.2 ± 0.2 × 1010   cm-2 s-1, referred to the surface. If horizontal variations in temperature and H2 density are small, this upward flux also represents the escape flux from the atmosphere. The CH4 density exhibits significant horizontal variations that are likely an indication of dynamical processes in the upper atmosphere.

Original languageEnglish (US)
Pages (from-to)567-576
Number of pages10
JournalIcarus
Volume182
Issue number2
DOIs
StatePublished - Jun 2006

Fingerprint

Titan
upper atmosphere
mass spectrometers
spectrometer
escape
ion
ions
temperature
vertical mixing
atmospheric temperature
turbulent diffusion
stratosphere
eddy
spacecraft
profiles
air temperature
encounters
indication
diffusion coefficient
atmosphere

Keywords

  • Aeronomy
  • Planets

ASJC Scopus subject areas

  • Space and Planetary Science
  • Astronomy and Astrophysics

Cite this

Yelle, R., Borggren, N., de la Haye, V., Kasprzak, W. T., Niemann, H. B., Müller-Wodarg, I., & Waite, J. H. (2006). The vertical structure of Titan's upper atmosphere from Cassini Ion Neutral Mass Spectrometer measurements. Icarus, 182(2), 567-576. https://doi.org/10.1016/j.icarus.2005.10.029

The vertical structure of Titan's upper atmosphere from Cassini Ion Neutral Mass Spectrometer measurements. / Yelle, Roger; Borggren, N.; de la Haye, V.; Kasprzak, W. T.; Niemann, H. B.; Müller-Wodarg, I.; Waite, J. H.

In: Icarus, Vol. 182, No. 2, 06.2006, p. 567-576.

Research output: Contribution to journalArticle

Yelle, R, Borggren, N, de la Haye, V, Kasprzak, WT, Niemann, HB, Müller-Wodarg, I & Waite, JH 2006, 'The vertical structure of Titan's upper atmosphere from Cassini Ion Neutral Mass Spectrometer measurements', Icarus, vol. 182, no. 2, pp. 567-576. https://doi.org/10.1016/j.icarus.2005.10.029
Yelle, Roger ; Borggren, N. ; de la Haye, V. ; Kasprzak, W. T. ; Niemann, H. B. ; Müller-Wodarg, I. ; Waite, J. H. / The vertical structure of Titan's upper atmosphere from Cassini Ion Neutral Mass Spectrometer measurements. In: Icarus. 2006 ; Vol. 182, No. 2. pp. 567-576.
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