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Published April 10, 2013 | Published
Journal Article Open

Microscopic emission and reflectance thermal infrared spectroscopy: instrumentation for quantitative in situ mineralogy of complex planetary surfaces

Abstract

The diversity of investigations of planetary surfaces, especially Mars, using in situ instrumentation over the last decade is unprecedented in the exploration history of our solar system. The style of instrumentation that landed spacecraft can support is dependent on several parameters, including mass, power consumption, instrument complexity, cost, and desired measurement type (e.g., chemistry, mineralogy, petrology, morphology, etc.), all of which must be evaluated when deciding an appropriate spacecraft payload. We present a laboratory technique for a microscopic emission and reflectance spectrometer for the analysis of martian analog materials as a strong candidate for the next generation of in situ instruments designed to definitively assess sample mineralogy and petrology while preserving geologic context. We discuss the instrument capabilities, signal and noise, and overall system performance. We evaluate the ability of this instrument to quantitatively determine sample mineralogy, including bulk mineral abundances. This capability is greatly enhanced. Whereas the number of mineral components observed from existing emission spectrometers is high (often >5 to 10 depending on the number of accessory and alteration phases present), the number of mineral components at any microscopic measurement spot is low (typically <2 to 3). Since this style of instrument is based on a long heritage of thermal infrared emission spectrometers sent to orbit (the thermal emission spectrometer), sent to planetary surfaces [the mini-thermal emission spectrometers (mini-TES)], and evaluated in laboratory environments (e.g., the Arizona State University emission spectrometer laboratory), direct comparisons to existing data are uniquely possible with this style of instrument. The ability to obtain bulk mineralogy and atmospheric data, much in the same manner as the mini-TESs, is of significant additional value and maintains the long history of atmospheric monitoring for Mars. Miniaturization of this instrument has also been demonstrated, as the same microscope objective has been mounted to a flight-spare mini-TES. Further miniaturization of this instrument is straightforward with modern electronics, and the development of this instrument as an arm-mounted device is the end goal.

Additional Information

© 2013 Optical Society of America. Received 9 November 2012; accepted 14 February 2013; posted 21 February 2013 (Doc. ID 179165); published 3 April 2013. We thank William O'Donnell for the many hours of assistance in assembling, aligning, and optimizing this instrument spent in the laboratory. We also thank Stillman Chase, Greg Mehall, and Elliot Burke for detailed discussions and input on the overall instrument design and construction. Furthermore, we thank Steven Ruff, who added significant contributions to the design and calibration of this instrument and provided input on the direction of this manuscript. We also thank Michael Veto who reviewed an early draft of this manuscript. This work was funded through the NASA Planetary Geology and Geophysics research program (grant NNX08AM63G) and the Mars Instrument Development Program (grant NNX08AR07G).

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August 19, 2023
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