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Impact and Collisional Processes in the Solar SystemIn the past year, we have successfully developed the techniques necessary to conduct impact experiments on ice at very low temperatures. We employ the method of embedding gauges within a target to measure the shock wave and material properties. This means that our data are not model dependent; we directly measure the essential parameters needed for numerical simulations of impact cratering. Since then we have developed a new method for temperature control of icy targets that ensures temperature equilibrium throughout a porous target. Graduate student, Sarah Stewart-Mukhopadhyay, is leading the work on ices and porous materials as the main thrust of her thesis research. Our previous work has focused on icy materials with no porosity, and we propose to extend our research to include porous ice and porous ice-silicate mixtures. There is little shockwave data for porous ice, and none of the data was acquired under conditions applicable to the outer solar system. The solid ice Hugoniot is only defined for initial temperatures above -20 C. Our program uniquely measures the properties of ice at temperatures directly applicable to the solar system. Previous experiments were conducted at ambient temperatures soon after removing the target from a cold environment, usually just below freezing, or in a room just below freezing. Since ice has an extremely complicated phase diagram, it is important to conduct experiments at lower temperatures to determine the true outcome of impacts in the outer solar system. This research is complementary to other programs on icy materials. Our work focuses on the inherent material properties by measuring the shock wave directly; this complements the macroscopic observations and immediately provides the parameters necessary to extend this research to the gravity regime. Our numerical simulations of impacts in porous ice under very low gravity conditions, such as found on comets, show that the final crater size and shape is very dependent on the dynamic strength of the material.
Document ID
20010069199
Acquisition Source
Goddard Space Flight Center
Document Type
Contractor or Grantee Report
Authors
Ahrens, Thomas J. (California Inst. of Tech. Pasadena, CA United States)
Date Acquired
September 7, 2013
Publication Date
July 5, 2001
Subject Category
Astrophysics
Report/Patent Number
CIT-TJA.00003-1-NASA.000018
Funding Number(s)
CONTRACT_GRANT: NAG5-8907
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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