HR: 1340h
AN: MR23A-1021    [Abstracts]
TI: Planetary ices up close: imaging by cryogenic SEM.
AU: * Stern, L A
EM: lstern@usgs.gov
AF: USGS, 345 Middlefield Rd., Menlo Park, CA 94025, United States
AU: Durham, W B
EM: wbdurham@mit.edu
AF: MIT, Dept. of Earth & Planetary Sciences, Cambridge, MA 02139,
AU: Kirby, S H
EM: skirby@usgs.gov
AF: USGS, 345 Middlefield Rd., Menlo Park, CA 94025, United States
AU: McCarthy, C
EM: christine_mccarthy@brown.edu
AF: Brown University, Dept. of Geol. Sci., Providence, RI 02912,
AU: Kubo, T
EM: kubotomo@mac.com
AF: Kyushu Univ., Dept. Earth & Planet. Sci., Fukuoka, 812-8581, Japan
AU: Rieck, K
EM: karen.d.rieck@gmail.com
AF: ASU, Dept. Earth & Planet. Sci., Tempe, AZ 85287,
AU: Pathare, A
EM: avp11235@gmail.com
AF: Planetary Science Institute, Cal. Tech., Pasadena, CA 91125,
AB: Insight into the mechanical response of icy minerals and mixtures relevant to outer solar system environments comes not only from data and images of the solar-system objects themselves but also from laboratory study of these materials. Over the past several decades, we have conducted experimental research on the deformation behavior and microphysics of some of the principal rock-forming cryominerals within the C-O-H-N-S chemical systems and the multiphase rocks composed of them ( e.g. Durham et al. 1987; 1992; 1993; 1996; 1997; 2000; 2001; 2003a,b; 2005a,b,c; Durham & Stern 2001; Kubo et al. 2006; McCarthy et al. 2007; and references therein.) Our experimental approach has been to make reproducible samples with well-characterized grain sizes and textures for controlled deformation experiments, and then conduct post-test analyses to determine how deformation alters sample texture, phase composition, and phase distribution. Such characterization down to the microscopic level is necessary to evaluate the microphysics of flow, and is now routinely performed in our laboratory by means of cryogenic scanning electron microscopy (CSEM). With this technique we can resolve surface features down to a fraction of a micron and see evidence for processes that occur both during sample growth as well as during subsequent deformation. This technique also permits investigation into the physics of flow of two-phase solid alloys by directly observing how the phases articulate and interact. Phase identification is then determined by energy dispersive x-ray spectroscopy (EDS), or for bulk analysis, by cryogenic powder x-ray diffraction (XRD). Here, we present an overview of the cryominerals that we have synthesized, tested, and observed by CSEM to date, and the key results revealed or verified by the CSEM imaging process. These materials include: (1) H₂O ice I; including grain growth experiments, hydrostatic compaction of cold (< 120 K) ice I, and flow of fine-grained ice I with entrained impurities; (2) ice II in the regime of grain-size-sensitive (GSS) creep, (3) sI and sII gas clathrate hydrates and clathrates mixed with particulates; and (4) hydrated salts in the NaCl-H₂O, MgSO₄-H₂O, and Na₂SO₄-H₂O systems, and associated mixtures or eutectic compositions with water ice.
DE: 3620 Mineral and crystal chemistry (1042)
DE: 3924 High-pressure behavior
DE: 5422 Ices
DE: 5460 Physical properties of materials
DE: 8147 Planetary interiors (5430, 5724, 6024)
SC: Mineral and Rock Physics [MR]
MN: 2007 Fall Meeting