American Geophysical Union Become an AGU Member
Subscribe to AGU Journals		 AGU Home AGU Publications

Editor's Highlight

Read Full Article (file size: 1008983 bytes)    Cited by

GEOPHYSICAL RESEARCH LETTERS, VOL. 34, L22103, doi:10.1029/2007GL030978, 2007

Discovery of heavy negative ions in Titan's ionosphere

A. J. Coates

Mullard Space Science Laboratory, University College London, Dorking, UK
Centre for Planetary Sciences, University College London, London, UK


F. J. Crary

Space Science and Engineering Division, Southwest Research Institute, San Antonio, Texas, USA


G. R. Lewis

Mullard Space Science Laboratory, University College London, Dorking, UK
Centre for Planetary Sciences, University College London, London, UK


D. T. Young

Space Science and Engineering Division, Southwest Research Institute, San Antonio, Texas, USA


J. H. Waite Jr.

Space Science and Engineering Division, Southwest Research Institute, San Antonio, Texas, USA


E. C. Sittler Jr.

NASA/Goddard Space Flight Center, Greenbelt, Maryland, USA


Abstract

Titan's ionosphere contains a rich positive ion population including organic molecules. Here, using CAPS electron spectrometer data from sixteen Titan encounters, we reveal the existence of negative ions. These ions, with densities up to ∼100 cm−3, are in mass groups of 10–30, 30–50, 50–80, 80–110, 110–200 and 200+ amu/charge. During one low encounter, negative ions with mass per charge as high as 10,000 amu/q are seen. Due to their unexpectedly high densities at ∼950 km altitude, these negative ions must play a key role in the ion chemistry and they may be important in the formation of organic-rich aerosols (tholins) eventually falling to the surface.

Received 21 June 2007; accepted 19 October 2007; published 28 November 2007.

Keywords: Titan; negative ions; ionosphere.

Index Terms: 5435 Planetary Sciences: Solid Surface Planets: Ionospheres (2459); 6281 Planetary Sciences: Solar System Objects: Titan; 2459 Ionosphere: Planetary ionospheres (5435, 5729, 6026); 0305 Atmospheric Composition and Structure: Aerosols and particles (0345, 4801, 4906); 5470 Planetary Sciences: Solid Surface Planets: Surface materials and properties.

Read Full Article (file size: 1008983 bytes)    Cited by

Citation: Coates, A. J., F. J. Crary, G. R. Lewis, D. T. Young, J. H. Waite Jr., and E. C. Sittler Jr. (2007), Discovery of heavy negative ions in Titan's ionosphere, Geophys. Res. Lett., 34, L22103, doi:10.1029/2007GL030978.