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Mars Mineralogical Exploration: A New Generation of Leadership

Session: Advancing Mineral Science and Exploring Planetary Surfaces: In Honor of MSA Dana Medalist, Elizabeth B. Rampe, Part I

Presenting Author:

David Blake

Authors:

Blake, David Frederick¹, Vaniman, David T.²

(1) Exobiology Branch, NASA Ames Research Center Exobiology, Moffett Field, CA, USA; Hawai'i Institute of Geophysics and Planetology, University of Hawaii, Honolulu, Hawaii, USA, (2) Planetary Science Institute, Tucson, AZ, USA,

Abstract:

We began analyzing soils and rocks in Gale Crater, Mars with the CheMin X-ray Diffraction instrument in August 2012. In our original proposal to NASA, we claimed that we would identify and quantify all minerals present in a sample at greater than 3 wt. percent with an accuracy of 10 percent and a precision of 12 percent. This in itself would have resulted in a revolutionary improvement of our knowledge of the mineralogy and early geologic history of Mars. However, almost immediately, the next generation students and post-docs on our team (including Liz Rampe) began to devise ways to improve our analytical results. These improvements included using the plagioclase feldspar present in nearly all samples as an internal standard to correct for pattern displacement errors, and using full pattern fitting techniques to calculate the lattice parameters and quantity of each mineral phase and the amount of X-ray amorphous material present. We are now able to refine lattice parameters for each mineral phase and use equations derived from those parameters to determine the elemental composition of each mineral. Using the bulk composition from APXS measurements, we can calculate the composition of the amorphous component as well. With the new techniques devised by Liz Rampe and others on the team, we can now identify all minerals present at > 1 wt. percent, quantify the abundances of minerals present at > 3 wt. percent, determine their crystallographic structure states and cation occupancies, quantify the abundances of all major elements present in each mineral and determine their valence states. Improvements on these remote, robotic measurements by XRD can only be made through sample return and analysis in terrestrial laboratories. Liz Rampe became the CheMin’s Deputy PI in 2015 and has led the team through many of our analysis campaigns since that time. Liz is leading our proposals for next generation CheMin instruments to Mars, the Earth’s moon, and other destinations in the solar system.