Self-diffusion in high-pressure ices and implications for plastic flow in the interiors of the large icy bodies

2016 Fiscal Year Final Research Report

• Project/Area Number: 15K17795
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Multi-year Fund
• Research Field: Geochemistry/Cosmochemistry
• Research Institution: Okayama University
• Principal Investigator: Noguchi Naoki 岡山大学, 惑星物質研究所, 特別契約職員(助教) (50621760)
• Project Period (FY): 2015-04-01 – 2017-03-31
• Keywords: 高圧氷 / 拡散 / レオロジー / 氷天体 / 粘性 / プロトン

Outline of Final Research Achievements

The lifetimes of the internal ocean of large icy bodies till water freezes depend on the rheological properties of the high pressure polymorphs of H2O ice layers (HP-ice layer) underlying the internal oceans. The differential stress driving the conventions of the HP-ice layers is very low below 0.1 MPa. The rheological properties at low-stress condition can be inferred from their diffusivities and the theory of diffusion creep. Here, we have developed the method to determine diffusion coefficients of the high-pressure ices using a DAC and micro-Raman spectroscopy. First, to conduct the diffusion experiments, we have constructed the instrumental platforms such as a micro-Raman mapping system, and a Peltier-cooling DAC. Further, we determined the pressure-temperature dependences of the diffusion coefficients of ices VI and VII. The viscosities of HP-ices were inferred from their diffusivities, and the critical layer thickness below which convection cannot occur was estimated.

Free Research Field

地球惑星物質学