UCL Discovery
UCL home » Library Services » Electronic resources » UCL Discovery

Cassini CAPS Identification of Pickup Ion Compositions at Rhea

Desai, RT; Taylor, SA; Regoli, LH; Coates, AJ; Nordheim, TA; Cordiner, MA; Teolis, BD; ... Waite, JH; + view all (2018) Cassini CAPS Identification of Pickup Ion Compositions at Rhea. Geophysical Research Letters , 45 (4) pp. 1704-1712. 10.1002/2017GL076588. Green open access

[thumbnail of Coates_Cassini CAPS Identification of Pickup Ion Compositions at Rhea_VoR.pdf]
Preview
Text
Coates_Cassini CAPS Identification of Pickup Ion Compositions at Rhea_VoR.pdf - Published Version

Download (871kB) | Preview

Abstract

Saturn's largest icy moon, Rhea, hosts a tenuous surface‐sputtered exosphere composed primarily of molecular oxygen and carbon dioxide. In this Letter, we examine Cassini Plasma Spectrometer velocity space distributions near Rhea and confirm that Cassini detected nongyrotropic fluxes of outflowing CO_{2}^{+} during both the R1 and R1.5 encounters. Accounting for this nongyrotropy, we show that these possess comparable along‐track densities of ∼2 × 10⁻³ cm⁻³. Negatively charged pickup ions, also detected during R1, are surprisingly shown as consistent with mass 26 ± 3 u which we suggest are carbon‐based compounds, such as CN⁻, C₂H⁻, C_{2}^{-}, or HCO⁻, sputtered from carbonaceous material on the moon's surface. The negative ions are calculated to possess along‐track densities of ∼5 × 10⁻⁴ cm⁻³ and are suggested to derive from exogenic compounds, a finding consistent with the existence of Rhea's dynamic CO₂ exosphere and surprisingly low O₂ sputtering yields. These pickup ions provide important context for understanding the exospheric and surface ice composition of Rhea and of other icy moons which exhibit similar characteristics.

Type: Article
Title: Cassini CAPS Identification of Pickup Ion Compositions at Rhea
Open access status: An open access version is available from UCL Discovery
DOI: 10.1002/2017GL076588
Publisher version: http://dx.doi.org/10.1002/2017GL076588
Language: English
Additional information: © 2018. The Authors. This is an open access article under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/).
Keywords: Rhea, exosphere, icy satellites, pickup ions, plasma interactions
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Space and Climate Physics
URI: https://discovery.ucl.ac.uk/id/eprint/10044328
Downloads since deposit
Loading...
67Downloads
Download activity - last month
Loading...
Download activity - last 12 months
Loading...
Downloads by country - last 12 months
1.China
2
2.United States
1

Archive Staff Only

View Item View Item