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Numerical Investigations of Hydrated Mineral Formation on Small-Body Surfaces

Author: 
Barbara Cohen
Topic: 
Asteroid Population Characterization
Delivered As: 
Oral
Abstract Text: 

Extraterrestrial water-bearing minerals are of great importance both for understanding the formation and evolution of the solar system and for supporting future human activities in space. The presence of water is thought to be one of the necessary conditions for the formation of life as we know it. Furthermore, the long-term survival of human-staffed bases on other planets is critically dependent upon the existence and exploitation of an easily reached water source.

The presence of 3-μm absorption features on some, but not all, asteroids tells us that hydrated minerals can persist on the surface of airless bodies, presumably since early in solar system history. If hydrated mineral signatures were found on all asteroids, in all classes, it would suggest an exogenic process (e.g., surficial generation of OH by -wind reactions on silicates or micrometeorite impacts) as the origin of the hydrated minerals. However, because the S asteroids (ordinary chondrites) as a group do not have 3-um absorption features and so are are unlikely to have hydrated minerals compared to the C-class asteroids, we can infer that the hydrated mineralogy of the asteroid classes is an intrinsic compositional difference, and that the hydrated minerals are a product of parent-body processee. We are using physics- and chemistry-based models to investigate whether formation of hydrated minerals can occur in the surface and near-surface environments of carbonaceous type asteroids. These models will elucidate how the conditions within the parent body that cause internal aqueous alteration play themselves out at the asteroid’s surface.

We explored the present state of the art for modeling of evolution of small bodies in the solar system. The goal was to determine if existing tools could model the thermochemical evolution of CM asteroid parent bodies with adequate fidelity. It was found that all existing methods were deficient in one way or another for this task. For example, they assumed uniform material properties or ignored gas and fluid flow. These assumptions were adequate for the models the respective tools were designed for, but not the modeling of CM parent bodies. A second task was to determine if the Comsol code could be used to solve this problem. Comsol is a multiphysics solver package that could, theoretically, solve any set of PDEs or ODEs posed to it. Using a trial version of the code, it was found that the demanding time-step range of the problem, which spans from seconds to millions of years, was too severe for the Comsol solvers to handle. We continue to investigate the feasibility of modifying existing tools to this specific task.

Co-Authors: 
M. Shirley (NASA Ames Research Center, Moffett Field, CA 94035 USA "...
SSERVI Identifier: 
NESF2016-028

About SSERVI
Recognizing that science and human exploration are mutually enabling, NASA created the Solar System Exploration Research Virtual Institute (SSERVI) to address basic and applied scientific questions fundamental to understanding the Moon, Near Earth Asteroids, the Martian moons Phobos and Deimos, and the near space environments of these target bodies. As a virtual institute, SSERVI funds investigators at a broad range of domestic institutions, bringing them together along with international partners via virtual technology to enable new scientific efforts."