Thermal Emission Spectroscopy of Zeolite Minerals

Introduction and background: Zeolite minerals are hydrated framework aluminosilicates common to altered volcanic and volcanoclastic rocks, and the soils derived from them [1]. The mineralogy, chemistry, textural context, and abundance of zeolites provides insight into chemical weathering, hydrothermal, and metamorphic processes on Earth, in a variety of climates and tectonic settings. Zeolites could also be important minerals on Mars, where they may occur as cements in soils and sedimentary rocks, replacements in altered tuffs, amygdules or veins/veinlets in altered lavas, or in the dust [2]. Identification of zeolites on Mars could point to past alkaline, saline lacustrine environments, or chemical weathering processes related to alkaline, high-pH regimes [1]. Infrared spectroscopy provides an opportunity to identify zeolites on Mars, and as such, it is important to study the infrared spectral features of zeolites to enable their remote detection. In this study, we build on previous work by [3], which discusses the reflectance spectra of a suite of zeolite minerals, focusing on the visible-near infrared (VNIR) (λ ≅ 0.5-4 μm) region. Here, we produce thermal infrared emission spectra (λ ≅ 6-30 μm) of zeolites, relating their crystal chemical properties to their spectral features. This is necessary groundwork for evaluating the alteration state of Mars from infrared measurements.