Thermal Infrared Spectra of Mineral Mixtures Under Simulated Airless Body Conditions: Application to Diviner Lunar Radiometer
Abstract
On airless bodies, the uppermost portion of regolith, the "epiregolith", represents the boundary layer between the surface and space that dominates spectral observations from far-ultraviolet reflectance to far- infrared emission. On the Moon, this layer is typically less than 2 mm in thickness and is characterized by significant thermal gradients (~60K / 100 μm). These thermal gradients make spectral emission from the Moon wholly different from Earth and Mars (where the epiregolith is essentially isothermal) and complicate the interpretation of spectral emission remote sensing data. Therefore, thermal infrared (TIR) spectroscopy experiments and spectral libraries measured in ambient laboratory conditions are not comparable to remote sensing datasets of airless bodies that contain significant emission components.
We work to overcome this challenge by measuring TIR emission spectra in a chamber that simulates the relevant environment. The Simulated Airless Body Emission Laboratory (SABEL) chamber at the Johns Hopkins Applied Physics Laboratory illuminates and heats particulate samples under vacuum to generate a thermal gradient akin to that found in the epiregolith of airless bodies. Simulating the lunar environment in SABEL allows us to measure TIR spectra that are directly comparable to remotely sensed TIR observations from the Diviner Lunar Radiometer (Diviner) instrument aboard the Lunar Reconnaissance Orbiter (LRO). Here we present an application of SABEL to characterize the TIR emission spectra of two- and three-component silicate mineral mixtures with the endmembers plagioclase, pyroxene, and olivine. These uniform composition and particle-size endmembers bound the typical mineral compositions of the lunar surface. By understanding the TIR characteristics of these mixtures, we can better interpret TIR data and their implications for surface composition on the Moon and other airless bodies.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.P32A..04G
- Keywords:
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- 0758 Remote sensing;
- CRYOSPHERE;
- 5410 Composition;
- PLANETARY SCIENCES: SOLID SURFACE PLANETS;
- 5464 Remote sensing;
- PLANETARY SCIENCES: SOLID SURFACE PLANETS