Spectral masking of goethite in abandoned mine drainage systems: implications for Mars

Earth and Planetary Science Letters
By: , and 

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Abstract

Remote sensing studies of the surface of Mars use visible- to near-infrared (VNIR) spectroscopy to identify hydrated and hydroxylated minerals, which can be used to constrain past environmental conditions on the surface of Mars. However, due to differences in optical properties, some hydrated phases can mask others in VNIR spectra, complicating environmental interpretations. Here, we examine the role of masking in VNIR spectra of natural precipitates of ferrihydrite, schwertmannite, and goethite from abandoned mine drainage (AMD) systems in southeastern Pennsylvania. Mixtures of ferrihydrite, schwertmannite, and goethite were identified in four AMD sites by using X-ray diffractometry (XRD), and their XRD patterns compared to their VNIR spectra. We find that both ferrihydrite and schwertmannite can mask goethite in VNIR spectra of natural AMD precipitates. These findings suggest that care should be taken in interpreting environments on Mars where ferrihydrite, schwertmannite, or goethite are found, as the former two may be masking the latter. Additionally, our findings suggest that outcrops on Mars with both goethite and ferrihydrite/schwertmannite VNIR signatures may have high relative abundances of goethite, or the goethite may exist in a coarsely crystalline phase.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Spectral masking of goethite in abandoned mine drainage systems: implications for Mars
Series title Earth and Planetary Science Letters
DOI 10.1016/j.epsl.2014.06.045
Volume 403
Year Published 2014
Language English
Publisher Elsevier
Contributing office(s) Pennsylvania Water Science Center
Description 8 p.
Larger Work Type Article
Larger Work Subtype Journal Article
Larger Work Title Earth and Planetary Science Letters
First page 217
Last page 224
Country United States
State Pennsylvania
County Schuylkill County