Weakening of ice by magnesium perchlorate hydrate

I show that perchlorate hydrates, which have been indirectly detected at high Martian circumpolar latitudes by the Phoenix Mars Lander, have a dramatic effect upon the rheological behavior of polycrystalline water ice under conditions applicable to the north polar layered deposits (NPLD). I conducted subsolidus creep tests on mixtures of ice and magnesium perchlorate hexahydrate (MP6) of 0.02, 0.05, 0.10, and 0.47 volume fraction MP6. I found these mixtures to be increasingly weak with increasing MP6 content. For mixtures with </= 0.10 volume fraction MP6, I resolved a stress exponent of n ~~ 2 at low stresses transitioning to n ~~ 4 above 10 MPa. Scanning electron microscopy of deformed specimens revealed MP6 to be distributed as an interconnected film between ice grains. These results suggest that grain boundary sliding (GBS) may be enhanced with respect to pure ice. As the enhancement of GBS is expected in polycrystalline aggregates containing a few percent melt or otherwise weak material distributed along grain boundaries, the observed n~~ 2 is consistent with the mutual accommodation of basal slip and GBS. If ice containing trace concentrations of MP6 is also much weaker than pure ice at low stresses, flow in the NPLD could be significantly enhanced, particularly at the warmer basal temperatures associated with higher Martian obliquities.

Department dc:contributor.department

Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2012

Author dc:creator

• Lenferink, Hendrik J., 1985-

Advisor dc:contributor.advisor

• William B. Durham.

• Earth, Atmospheric, and Planetary Sciences.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/78478

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/78478