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Title: Active Cryovolcanism on Europa?

Abstract

Evidence for plumes of water on Europa has previously been found using the Hubble Space Telescope using two different observing techniques. Roth et al. found line emission from the dissociation products of water. Sparks et al. found evidence for off-limb continuum absorption as Europa transited Jupiter. Here, we present a new transit observation of Europa that shows a second event at the same location as a previous plume candidate from Sparks et al., raising the possibility of a consistently active source of erupting material on Europa. This conclusion is bolstered by comparison with a nighttime thermal image from the Galileo Photopolarimeter-Radiometer that shows a thermal anomaly at the same location, within the uncertainties. The anomaly has the highest observed brightness temperature on the Europa nightside. If heat flow from a subsurface liquid water reservoir causes the thermal anomaly, its depth is ≈1.8–2 km, under simple modeling assumptions, consistent with scenarios in which a liquid water reservoir has formed within a thick ice shell. Models that favor thin regions within the ice shell that connect directly to the ocean, however, cannot be excluded, nor modifications to surface thermal inertia by subsurface activity. Alternatively, vapor deposition surrounding an active vent could increasemore » the thermal inertia of the surface and cause the thermal anomaly. This candidate plume region may offer a promising location for an initial characterization of Europa’s internal water and ice and for seeking evidence of Europa’s habitability.« less

Authors:
; ;  [1];  [2];  [3];  [4];  [5]
  1. Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)
  2. Georgia Institute of Technology, School of Earth and Atmospheric Sciences, 311 Ferst Drive, Atlanta, GA 30332 (United States)
  3. SETI Institute, 189 N. Bernardo Avenue, Mountain View, CA 94043 (United States)
  4. Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States)
  5. Southwest Research Institute, 1050 Walnut Street, Suite 300, Boulder, CO 80302 (United States)
Publication Date:
OSTI Identifier:
22654492
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal Letters; Journal Volume: 839; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABSORPTION; BRIGHTNESS; DISSOCIATION; EMISSION; HEAT FLUX; ICE; JUPITER PLANET; LIMBS; LIQUIDS; MODIFICATIONS; MOMENT OF INERTIA; RADIOMETERS; SATELLITES; SHELL MODELS; SIMULATION; SPACE; SURFACES; TELESCOPES; WATER; WATER RESERVOIRS

Citation Formats

Sparks, W. B., Cracraft, M., Deustua, S. E, Schmidt, B. E., McGrath, M. A., Hand, K. P., and Spencer, J. R., E-mail: sparks@stsci.edu. Active Cryovolcanism on Europa?. United States: N. p., 2017. Web. doi:10.3847/2041-8213/AA67F8.
Sparks, W. B., Cracraft, M., Deustua, S. E, Schmidt, B. E., McGrath, M. A., Hand, K. P., & Spencer, J. R., E-mail: sparks@stsci.edu. Active Cryovolcanism on Europa?. United States. doi:10.3847/2041-8213/AA67F8.
Sparks, W. B., Cracraft, M., Deustua, S. E, Schmidt, B. E., McGrath, M. A., Hand, K. P., and Spencer, J. R., E-mail: sparks@stsci.edu. Thu . "Active Cryovolcanism on Europa?". United States. doi:10.3847/2041-8213/AA67F8.
@article{osti_22654492,
title = {Active Cryovolcanism on Europa?},
author = {Sparks, W. B. and Cracraft, M. and Deustua, S. E and Schmidt, B. E. and McGrath, M. A. and Hand, K. P. and Spencer, J. R., E-mail: sparks@stsci.edu},
abstractNote = {Evidence for plumes of water on Europa has previously been found using the Hubble Space Telescope using two different observing techniques. Roth et al. found line emission from the dissociation products of water. Sparks et al. found evidence for off-limb continuum absorption as Europa transited Jupiter. Here, we present a new transit observation of Europa that shows a second event at the same location as a previous plume candidate from Sparks et al., raising the possibility of a consistently active source of erupting material on Europa. This conclusion is bolstered by comparison with a nighttime thermal image from the Galileo Photopolarimeter-Radiometer that shows a thermal anomaly at the same location, within the uncertainties. The anomaly has the highest observed brightness temperature on the Europa nightside. If heat flow from a subsurface liquid water reservoir causes the thermal anomaly, its depth is ≈1.8–2 km, under simple modeling assumptions, consistent with scenarios in which a liquid water reservoir has formed within a thick ice shell. Models that favor thin regions within the ice shell that connect directly to the ocean, however, cannot be excluded, nor modifications to surface thermal inertia by subsurface activity. Alternatively, vapor deposition surrounding an active vent could increase the thermal inertia of the surface and cause the thermal anomaly. This candidate plume region may offer a promising location for an initial characterization of Europa’s internal water and ice and for seeking evidence of Europa’s habitability.},
doi = {10.3847/2041-8213/AA67F8},
journal = {Astrophysical Journal Letters},
number = 2,
volume = 839,
place = {United States},
year = {Thu Apr 20 00:00:00 EDT 2017},
month = {Thu Apr 20 00:00:00 EDT 2017}
}
  • Voyager-derived data on the albedos of Europa are presently photometrically corrected and converted into average, single-scattering form, in order to analyze them as a function of angular distance from the apex of orbital motion. A hypothesized magnetospheric modification of the Europa surface is confirmed by the UV absorption found in the 0.35-micron filter data; this absorption directly correlates with the longitudinal ion implantation distribution in both terrain types. A red spectrum is found in both terrain types as well, and is found to be constant across the surface. A uniform increase is noted in the dark terrain absorption over thatmore » in the bright terrain. 43 references.« less
  • The creation of pathways for resurfacing of water or volatiles in a model of Europa in which an ocean underlies a thin ice shell is subjected to linear elastic fracture mechanical treatment. The gas-filled portion of the upward-propagating cracks pinches off from the water-filled portion, and may rapidly rise to the surface. The eruption thus generated is at first dominated by gas, but may subsequently include a less extended foam eruption; there may be no direct relationship between this resurfacing phenomenon and the geological features thus far noted on the Europa surface. 33 references.
  • An examination is conducted of Europa's cross-cutting structural relationships between various lineament types, in order to constrain the type of structure involved in each such case and, where possible, to also constrain the degree of extension across the lineaments. Evidence is adduced for significant lateral crustal movement, allowing alternative models and mechanisms for lineament formation to be discussed, as well as plausible lithospheric and crustal models. The question as to whether any of the water-ice layer has been, or currently is, liquid, is also treated in light of the evidence obtained. 53 refs.