The composition and structure of Enceladus' plume from the complete set of Cassini UVIS occultation observations

• Published in: Icarus (New York, N.Y. 1962) Vol. 344; p. 113461
• Main Authors: Hansen, C.J., Esposito, L.W., Colwell, J.E., Hendrix, A.R., Portyankina, G., Stewart, A.I.F., West, R.A.
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 01.07.2020
• ISSN: 0019-1035; 1090-2643
• DOI: 10.1016/j.icarus.2019.113461

Observations acquired at ultraviolet wavelengths are uniquely well-suited to investigate the composition and structure of Enceladus' plume. This paper describes the observations, analysis techniques and results of all the Enceladus occultations observed by Cassini's Ultraviolet Imaging Spectrograph (UVIS) and other observations designed to study the plume. Limits on gas at non-polar latitudes are derived. Constraints on the minor constituents' composition of Enceladus' primarily water vapor plume are evaluated. The overall source rate variability over a time span of 13 years is < 15%, although gas output in collimated supersonic jets may vary diurnally. The average source rate for water molecules is 300 kg/s. Local enhancement of gas in the plume due to supersonic gas jets is still detectable at heights over 100 km. •We describe the data, analysis, and results of all Enceladus occultations observed by the Cassini ultraviolet instrument.•Constraints on the minor constituents’ composition of Enceladus’ primarily water vapor plume are evaluated.•The overall source rate variability over a time span of 13 years is < 15%, although gas output in collimated supersonic jets may vary diurnally.•The average source rate for water molecules is 300 kg/sec.•Local enhancement of gas in the plume due to supersonic gas jets is still detectable at heights over 100 km.