The stability and transport of carbon dioxide on Iapetus

Eric E. Palmer, Robert H. Brown

Research output: Contribution to journalArticle

16 Scopus citations

Abstract

Carbon dioxide has been detected associated with Iapetus' dark material by the Cassini spacecraft. This CO2 may be primordial and/or resulting from ongoing production by photolysis of water-ice in the presence of carbonaceous material [Allamandola, L.J., Sandford, S.A., Valero, G.J., 1988. Icarus 76, 225-252]. Although any primordial CO2 would likely be complexed with the dark material and thus stable against thermal transport to Iapetus' poles [Buratti, B.J., and 28 colleagues, 2005. Astrophys. J. 622, L149-L152], active production of CO2 would result in some fraction of the CO2 being mobile enough to allow the accumulation of CO2 at Iapetus' poles. We develop a computer model to simulate ballistic transport of CO2 ice on Iapetus, accounting for Iapetus' gravitational binding energy and polar cold traps. We find that the residence time of CO2 ice outside the polar regions is very short; a sheet of CO2 ice near the equator of Iapetus decreases in thickness at a rate of 50 mm year-1. The sublimated CO2 will ballistically move around Iapetus until it reaches the polar cold traps where it can be sequestered for up to 15 years. If the total surface inventory of CO2 exceeds 3 × 107 kg, the polar ice cap will be permanent. While CO2 is moving around the surface, a small percentage will eventually reach escape velocity and be lost from the system. As such, a seasonal polar cap is lost at rate of 12% every solar orbit as the CO2 moves between the two polar cold traps.

Original languageEnglish (US)
Pages (from-to)434-446
Number of pages13
JournalIcarus
Volume195
Issue number1
DOIs
StatePublished - May 1 2008

Keywords

  • Iapetus
  • Ices

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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