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Title: Tidally modulated eruptions on Enceladus: Cassini ISS observations and models

We use images acquired by the Cassini Imaging Science Subsystem (ISS) to investigate the temporal variation of the brightness and height of the south polar plume of Enceladus. The plume's brightness peaks around the moon's apoapse, but with no systematic variation in scale height with either plume brightness or Enceladus' orbital position. We compare our results, both alone and supplemented with Cassini near-infrared observations, with predictions obtained from models in which tidal stresses are the principal control of the eruptive behavior. There are three main ways of explaining the observations: (1) the activity is controlled by right-lateral strike slip motion; (2) the activity is driven by eccentricity tides with an apparent time delay of about 5 hr; (3) the activity is driven by eccentricity tides plus a 1:1 physical libration with an amplitude of about 0.°8 (3.5 km). The second hypothesis might imply either a delayed eruptive response, or a dissipative, viscoelastic interior. The third hypothesis requires a libration amplitude an order of magnitude larger than predicted for a solid Enceladus. While we cannot currently exclude any of these hypotheses, the third, which is plausible for an Enceladus with a subsurface ocean, is testable by using repeat imaging of themore » moon's surface. A dissipative interior suggests that a regional background heat source should be detectable. The lack of a systematic variation in plume scale height, despite the large variations in plume brightness, is plausibly the result of supersonic flow; the details of the eruption process are yet to be understood.« less
Authors:
 [1] ; ;  [2]
  1. Department of Earth and Planetary Sciences, University of California, Santa Cruz, CA 95064 (United States)
  2. CICLOPS, Space Science Institute, Boulder, CO 80304 (United States)
Publication Date:
OSTI Identifier:
22342269
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astronomical Journal (New York, N.Y. Online); Journal Volume: 148; Journal Issue: 3; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; AMPLITUDES; BRIGHTNESS; COMPARATIVE EVALUATIONS; ERUPTION; FORECASTING; HEAT SOURCES; HYPOTHESIS; IMAGES; MOON; PLANETS; SCALE HEIGHT; SOLIDS; STRESSES; SUPERSONIC FLOW; SURFACES; TIME DELAY; VARIATIONS