Effects of dispersed particulates on the rheology of water ice at planetary conditions

Journal Article · Fri Dec 25 04:00:00 EST 1992 · Journal of Geophysical Research; (United States)

DOI:https://doi.org/10.1029/92JE02326· OSTI ID:6873808

Durham, W B ^[1]; Kirby, S H; Stern, L A ^[2]

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1. Lawrence Livermore National Lab., CA (United States)
2. Geological Survey, Menlo Park, CA (United States)

The authors have investigated the effects of initial grain size and hard particulate impurities on the transient and steady state flow of water ice I at laboratory conditions selected to provide more quantitative constraints on the thermomechanical evolution of the giant icy moons of the outer solar system. The samples were molded with particulate volume fractions, [phi], of 0.001 to 0.56 and particle sizes of 1 to 150 [mu]m. Deformation experiments were conducted at constant shortening rates of 4.4 [times] 10[sup [minus]7] to 4.9 [times] 10[sup [minus]4] s[sup [minus]1] at pressures of 50 and 100 MPa and temperatures 77 to 223 K. For the pure ice samples, initial grain sizes were 0.2-0.6 mm, 0.75-1.75 mm, and 1.25-2.5 mm. Stress-strain curves of pure ice I under these conditions display a strength maximum [sigma][sub u] at plastic strains [var epsilon] [le]0.01 after initial yield, followed by strain softening and achievement of steady state levels of stress, [sigma][sub ss], at [var epsilon] = 0.1 to 0.2. Mixed-phase ice with particulate concentrations [phi] [ge]0.1 is significantly stronger than pure ice; the strength of samples with [phi] = 0.56 approaches that of dry confined sand. The magnitude of the strengthening effect is far greater than expected from homogeneous strain-rate enhancement in the ice fraction or from pinning of dislocations (Orowan hardening). This result suggests viscous drag occurs in the ice as it flows around the hard particulates. Mixed-phase ice is also tougher than pure ice, extending the range of bulk plastic deformation versus faulting to lower temperatures and higher strain rates. Bulk planetary compositions of ice + rock ([phi] = 0.4-0.5) are roughly 2 orders of magnitude more viscous than pure ice, promoting the likelihood of thermal instability inside giant icy moons and possibly explaining the retention of crater topography on icy planetary surfaces. 34 refs., 14 figs., 3 tabs.

• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 6873808
• Journal Information: Journal of Geophysical Research; (United States), Journal Name: Journal of Geophysical Research; (United States) Vol. 97:E12; ISSN JGREA2; ISSN 0148-0227
• Country of Publication: United States
• Language: English

Related Subjects

661300* -- Other Aspects of Physical Science-- (1992-)
665000 -- Physics of Condensed Matter-- (1992-)
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
CONSTRAINTS
CRYSTAL DEFECTS
CRYSTAL STRUCTURE
DEFORMATION
DISLOCATIONS
DRAG
GEOLOGY
GRAIN SIZE
HARDENING
HIGH PRESSURE
HYDROGEN COMPOUNDS
ICE
IMPURITIES
INSTABILITY
LINE DEFECTS
MICROSTRUCTURE
NUCLEATION
OXYGEN COMPOUNDS
PARTICLES
PARTICULATES
PETROGRAPHY
RETENTION
RHEOLOGY
SIZE
SOLAR SYSTEM
STRAIN RATE
STRAIN SOFTENING
STRAINS
STRESSES
SURFACES
TEMPERATURE RANGE
TEMPERATURE RANGE 0065-0273 K
TEXTURE
TOPOGRAPHY
WATER