TERRESTRIAL SEA-ICE MORPHOLOGY - CONSIDERATIONS FOR EUROPA

Citation
R. Greeley et al., TERRESTRIAL SEA-ICE MORPHOLOGY - CONSIDERATIONS FOR EUROPA, Icarus (New York, N.Y. 1962), 135(1), 1998, pp. 25-40
Citations number
48
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Astronomy & Astrophysics
ISSN journal
0019-1035
Volume
135
Issue
1
Year of publication
1998
Pages
25 - 40
Database
ISI
SICI code
0019-1035(1998)135:1<25:TSM-CF>2.0.ZU;2-R
Abstract
The Galileo mission has returned the first high-resolution (21 m/pixel ) images of the surface of Europa, These images reveal structures with morphologies reminiscent of those seen on terrestrial sea ice. Althou gh it is premature to make one-to-one analogies between sea ice and Eu ropa's surface, a review of the types of surface features commonly for med on Earth and of various sea-ice processes can provide insight into the complex geology of Europa. For example, deformation of terrestria l sea ice results from winds, tides, and currents and from thermally i nduced stresses; the resulting features include fractures ranging in w idth from millimeters to kilometers, pressure ridges, shear ridges, an d rafted ice. Potential agents of deformation on Europa are more likel y to be limited to tidal flexing and possibly convection, but could pr oduce similar features and perhaps account for the ridges and fracture s seen in many areas. Subtle differences in albedo and color in terres trial sea ice result from differences in ice thickness and grain size, attributed to factors such as the rate of ice-crystal growth, water t urbulence, age of the ice, and deformation. Similar factors could acco unt for differences observed in the bright icy plains of Europa, Moreo ver, salts in both the solid form and as brine vary in concentration a nd composition as a function of space and time on Earth, leading to di fferences in density and the strength of ice sheets. Salts are also su spected in the europan ice and could lead to similar differences, enha ncing the creation of topographic relief from density contrasts and th e formation of fractures from brittle failure of the ice. Differences in the environments between Europa and terrestrial sea ice in terms of parameters such as temperature, gravity, time, and ice compositions s uggest caution in drawing direct analogies. Future work by the planeta ry and sea-ice communities must include understanding the terrestrial processes sufficiently for extrapolation in Europa. (C) 1998 Academic Press.