HR: 0800h
AN: P21B-0549    [Abstracts]
TI: Sill Injection on Icy Satellites Inferred from Ridge-Induced Flexure on Europa
AU: * Dombard, A J
EM: adombard@uic.edu
AF: Univ. of Illinois at Chicago, Dept. of Earth & Environmental Sciences 845 W. Taylor St. (MC-186), Chicago, IL 60607, United States
AU: Patterson, G W
EM: Wes.Patterson@jhuapl.edu
AF: Johns Hopkins Univ. Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, MD 20723, United States
AU: Prockter, L M
EM: Louise.Prockter@jhuapl.edu
AF: Johns Hopkins Univ. Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, MD 20723, United States
AB: There have been observations of active jetting from the south pole of Enceladus and evidence of past extrusions on other icy satellites, indicating that cryovolcanism is an important process in the outer solar system. In volcanic systems on Earth, the amount of subsurface magmatism generally exceeds the amount of surface volcanism. Given that the "magma" is denser than the "country rock," it is thus reasonable to expect subsurface cryomagmatism, although evidence has not been forthcoming. Here, we report that flexure caused by ridges, long, quasi-linear features ubiquitous over the face of the Europa, may indicate sill injection on this icy satellite. Studies of this flexure using simple elastic models determined effective elastic thicknesses of order 100 m to 1 km, implying very high heat flows (of order 1 W m^-2). Tidal dissipation and radiogenic heating within Europa probably cannot globally supply such high heat flows, suggesting there exists a mechanism to augment locally the thermal state. While there are several possibilities, we consider sill injection. We employ a thermomechanical finite-element model with an elastoviscoplastic rheology, and using the depth of neutral buoyancy as a guide, we simulate the thermal consequences of a sill and couple it to a mechanical simulation for ridge-induced flexure. The heat from this intrusion conducts through the ice and locally thins the lithosphere. For a case fit by an elastic plate 350 m thick (which translates into a heat flow of ~700 mW m^-2), we find a good fit to the data with a sill 1 km deep, 12 km wide, and persisting for 100 kyr. Notably, the regional heat flow is an order of magnitude lower (70 mW m^-2). Thus, indications of flexure at ridges may provide evidence of pervasive subsurface cryovolcanism on Europa and, by extension, on other icy satellites.
DE: 5418 Heat flow
DE: 5480 Volcanism (6063, 8148, 8450)
DE: 6221 Europa
SC: Planetary Sciences [P]
MN: 2007 Fall Meeting