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Controlled boiling on Enceladus. 1. Model of the vapor-driven jets

Nakajima, Miki and Ingersoll, Andrew P. (2016) Controlled boiling on Enceladus. 1. Model of the vapor-driven jets. Icarus, 272 . pp. 309-318. ISSN 0019-1035. http://resolver.caltech.edu/CaltechAUTHORS:20160520-082347025

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Abstract

Plumes of water vapor and ice particles have been observed from the so-called tiger stripes at the south polar terrain (SPT) of Saturn’s satellite, Enceladus. The observed high salinity (∼0.5–2%) of the ice particles in the plumes may indicate that the plumes originate from a subsurface liquid ocean. Additionally, the SPT is the source of strong infrared radiation (∼4.2 GW), which is especially intense near (within tens of meters) the tiger stripes. This could indicate that the radiation is associated with plume activity, but the connection remains unclear. Here we investigate the constraints that plume observations place on the widths of the cracks, the depth to the liquid-vapor interface, and the mechanisms controlling plume variability. We solve the fluid dynamics of the flow in the crack and the interaction between the flow and ice walls assuming that the flows of water vapor and ice particles originate from a few kilometers deep liquid ocean. For a crack with a uniform width, we find that our model could explain the observed vapor mass flow rate of the plumes when the crack width is 0.05–0.075 m. A wider crack is not favorable because it would produce a higher vapor mass flow rate than the observed value, but it may be allowed if there are some flows that do not reach the surface of Enceladus either due to condensation on the icy walls or the tortuosity of the crack. The observed heat flow can be explained if the total crack length is approximately 1.7 × 500 km. A tapering crack (a crack which is ∼1 m wide at the bottom of the flow and sharply becomes 0.05–0.075 m at shallower depths) can also explain the observed vapor mass flow rate and heat flow. Widths of 1 m or more are necessary to avoid freezing at the liquid-vapor interface, as shown in our paired paper (Ingersoll and Nakajima [2016] Icarus). The observed intense heat flow along the tiger stripes can be explained by the latent heat release due to vapor condensation onto the ice walls near the surface. The resulting buildup of ice causes the vents to seal themselves on time scales less than a year. We also find that the ice to vapor ratio of the plumes is sensitive to the ice mass fraction at the bottom of the flow (liquid–vapor interface). We find that the total mass flow rate of the plumes becomes larger when the crack width is larger, which is consistent with the observation that the flow rate increases near the orbital apocenter, where the crack is expected to be widest.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1016/j.icarus.2016.02.027DOIArticle
http://www.sciencedirect.com/science/article/pii/S0019103516000968PublisherArticle
Additional Information:© 2016 Elsevier Inc. Received 16 July 2015; Revised 13 February 2016; Accepted 17 February 2016; Available online 26 February 2016. We thank Alexey Pankine, the anonymous reviewer, and Carolyn Porco for insightful comments. This work was supported by NASA partly through the Cassini Project and partly through NASA’s Science Mission Directorate, Planetary Science, Grant/Contract/Agreement no. NNX15AH08G.
Funders:
Funding AgencyGrant Number
NASANNX15AH08G
Subject Keywords:Enceladus; Plumes; Jets; Ices; Icy satellites
Record Number:CaltechAUTHORS:20160520-082347025
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20160520-082347025
Official Citation:Miki Nakajima, Andrew P. Ingersoll, Controlled boiling on Enceladus. 1. Model of the vapor-driven jets, Icarus, Volume 272, 1 July 2016, Pages 309-318, ISSN 0019-1035, http://dx.doi.org/10.1016/j.icarus.2016.02.027. (http://www.sciencedirect.com/science/article/pii/S0019103516000968)
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:67196
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:20 May 2016 17:38
Last Modified:20 May 2016 17:38

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