Uncertainty Introduced by Darkening Agents in the Lunar Regolith: An Unmixing Perspective

On the Moon, in the near infrared wavelength range, spectral diagnostic features such as the 1-<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi mathvariant="sans-serif">μ</mi></semantics>...

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Autores principales:	Marcel Hess, Thorsten Wilhelm, Christian Wöhler, Kay Wohlfarth
Formato:	article
Lenguaje:	EN
Publicado:	MDPI AG 2021
Materias:	Moon unmixing space weathering Bayesian inference Science Q
Acceso en línea:	https://doaj.org/article/bc47897edff64382964db3e923b4e386
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spelling	oai:doaj.org-article:bc47897edff64382964db3e923b4e3862021-11-25T18:55:33ZUncertainty Introduced by Darkening Agents in the Lunar Regolith: An Unmixing Perspective10.3390/rs132247022072-4292https://doaj.org/article/bc47897edff64382964db3e923b4e3862021-11-01T00:00:00Zhttps://www.mdpi.com/2072-4292/13/22/4702https://doaj.org/toc/2072-4292On the Moon, in the near infrared wavelength range, spectral diagnostic features such as the 1-<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi mathvariant="sans-serif">μ</mi></semantics></math></inline-formula>m and 2-<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi mathvariant="sans-serif">μ</mi></semantics></math></inline-formula>m absorption bands can be used to estimate abundances of the constituent minerals. However, there are several factors that can darken the overall spectrum and dampen the absorption bands. Namely, (1) space weathering, (2) grain size, (3) porosity, and (4) mineral darkening agents such as ilmenite have similar effects on the measured spectrum. This makes spectral unmixing on the Moon a particularly challenging task. Here, we try to model the influence of space weathering and mineral darkening agents and infer the uncertainties introduced by these factors using a Markov Chain Monte Carlo method. Laboratory and synthetic mixtures can successfully be characterized by this approach. We find that the abundance of ilmenite, plagioclase, clino-pyroxenes and olivine cannot be inferred accurately without additional knowledge for very mature spectra. The Bayesian approach to spectral unmixing enables us to include prior knowledge in the problem without imposing hard constraints. Other data sources, such as gamma-ray spectroscopy, can contribute valuable information about the elemental abundances. We here find that setting a prior on TiO<sub>2</sub> and Al<sub>2</sub>O<sub>3</sub> can mitigate many of the uncertainties, but large uncertainties still remain for dark mature lunar spectra. This illustrates that spectral unmixing on the Moon is an ill posed problem and that probabilistic methods are important tools that provide information about the uncertainties, that, in turn, help to interpret the results and their reliability.Marcel HessThorsten WilhelmChristian WöhlerKay WohlfarthMDPI AGarticleMoonunmixingspace weatheringBayesian inferenceScienceQENRemote Sensing, Vol 13, Iss 4702, p 4702 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	Moon unmixing space weathering Bayesian inference Science Q
spellingShingle	Moon unmixing space weathering Bayesian inference Science Q Marcel Hess Thorsten Wilhelm Christian Wöhler Kay Wohlfarth Uncertainty Introduced by Darkening Agents in the Lunar Regolith: An Unmixing Perspective
description	On the Moon, in the near infrared wavelength range, spectral diagnostic features such as the 1-<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi mathvariant="sans-serif">μ</mi></semantics></math></inline-formula>m and 2-<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi mathvariant="sans-serif">μ</mi></semantics></math></inline-formula>m absorption bands can be used to estimate abundances of the constituent minerals. However, there are several factors that can darken the overall spectrum and dampen the absorption bands. Namely, (1) space weathering, (2) grain size, (3) porosity, and (4) mineral darkening agents such as ilmenite have similar effects on the measured spectrum. This makes spectral unmixing on the Moon a particularly challenging task. Here, we try to model the influence of space weathering and mineral darkening agents and infer the uncertainties introduced by these factors using a Markov Chain Monte Carlo method. Laboratory and synthetic mixtures can successfully be characterized by this approach. We find that the abundance of ilmenite, plagioclase, clino-pyroxenes and olivine cannot be inferred accurately without additional knowledge for very mature spectra. The Bayesian approach to spectral unmixing enables us to include prior knowledge in the problem without imposing hard constraints. Other data sources, such as gamma-ray spectroscopy, can contribute valuable information about the elemental abundances. We here find that setting a prior on TiO<sub>2</sub> and Al<sub>2</sub>O<sub>3</sub> can mitigate many of the uncertainties, but large uncertainties still remain for dark mature lunar spectra. This illustrates that spectral unmixing on the Moon is an ill posed problem and that probabilistic methods are important tools that provide information about the uncertainties, that, in turn, help to interpret the results and their reliability.
format	article
author	Marcel Hess Thorsten Wilhelm Christian Wöhler Kay Wohlfarth
author_facet	Marcel Hess Thorsten Wilhelm Christian Wöhler Kay Wohlfarth
author_sort	Marcel Hess
title	Uncertainty Introduced by Darkening Agents in the Lunar Regolith: An Unmixing Perspective
title_short	Uncertainty Introduced by Darkening Agents in the Lunar Regolith: An Unmixing Perspective
title_full	Uncertainty Introduced by Darkening Agents in the Lunar Regolith: An Unmixing Perspective
title_fullStr	Uncertainty Introduced by Darkening Agents in the Lunar Regolith: An Unmixing Perspective
title_full_unstemmed	Uncertainty Introduced by Darkening Agents in the Lunar Regolith: An Unmixing Perspective
title_sort	uncertainty introduced by darkening agents in the lunar regolith: an unmixing perspective
publisher	MDPI AG
publishDate	2021
url	https://doaj.org/article/bc47897edff64382964db3e923b4e386
work_keys_str_mv	AT marcelhess uncertaintyintroducedbydarkeningagentsinthelunarregolithanunmixingperspective AT thorstenwilhelm uncertaintyintroducedbydarkeningagentsinthelunarregolithanunmixingperspective AT christianwohler uncertaintyintroducedbydarkeningagentsinthelunarregolithanunmixingperspective AT kaywohlfarth uncertaintyintroducedbydarkeningagentsinthelunarregolithanunmixingperspective
_version_	1718410549951201280

Uncertainty Introduced by Darkening Agents in the Lunar Regolith: An Unmixing Perspective

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