A Spectral Investigation of Aqueously and Thermally Altered CM, CM-An, and CY Chondrites Under Simulated Asteroid Conditions for Comparison With OSIRIS-REx and Hayabusa2 Observations
JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS 126:7 (2021) ARTN e2021JE006827
Updates to the Oxford Space Environment Goniometer to measure visible wavelength bidirectional reflectance distribution functions in ambient conditions
Review of Scientific Instruments AIP Publishing 92:3 (2021) 034504
Abstract:Understanding how the surfaces of airless planetary bodies—such as the Moon—scatter visible light enables constraints to be placed on their surface properties and top boundary layer inputs to be set within thermal models. Remote sensing instruments—such as Diviner onboard the Lunar Reconnaissance Orbiter—measure thermal emission and visible light scattering functions across visible (∼0.38–0.7 µm) to thermal infrared (TIR) wavelengths (∼0.7–350 μm). To provide ground support measurements for such instruments, the Oxford Space Environment Goniometer (OSEG) was built. Initially, the OSEG focused on measuring TIR directional emissivity functions for regolith and regolith simulant samples in a simulated space environment, but it has recently been modified to measure visible wavelength Bidirectional Reflectance Distribution Functions (BRDFs) of samples in ambient conditions. Laboratory-measured BRDFs can be used (1) to test and to help interpret models—such as the Hapke photometric model—and (2) as visible scattering function inputs for thermal models. This paper describes the modifications to and initial calibration measurements taken by the Visible Oxford Space Environment Goniometer with a 532 nm laser, and details how this setup can be used to measure BRDFs of regolith and regolith simulant samples of airless planetary bodies.
Spectral Characterization of Bennu Analogs Using PASCALE: A New Experimental Set-Up for Simulating the Near-Surface Conditions of Airless Bodies.
Journal of geophysical research. Planets 126:2 (2021) e2020JE006624
Abstract:We describe the capabilities, radiometric stability, and calibration of a custom vacuum environment chamber capable of simulating the near-surface conditions of airless bodies. Here we demonstrate the collection of spectral measurements of a suite of fine particulate asteroid analogs made using the Planetary Analogue Surface Chamber for Asteroid and Lunar Environments (PASCALE) under conditions like those found on Earth and on airless bodies. The sample suite includes anhydrous and hydrated physical mixtures, and chondritic meteorites (CM, CI, CV, CR, and L5) previously characterized under Earth- and asteroid-like conditions. And for the first time, we measure the terrestrial and extra-terrestrial mineral end members used in the olivine- and phyllosilicate-dominated physical mixtures under the same conditions as the mixtures and meteorites allowing us better understand how minerals combine spectrally when mixed intimately. Our measurements highlight the sensitivity of thermal infrared emissivity spectra to small amounts of low albedo materials and the composition of the sample materials. As the albedo of the sample decreases, we observe smaller differences between Earth- and asteroid-like spectra, which results from a reduced thermal gradient in the upper hundreds of microns in the sample. These spectral measurements can be compared to thermal infrared emissivity spectra of asteroid (101955) Bennu's surface in regions where similarly fine particulate materials may be observed to infer surface compositions.
Author Correction: Shape of (101955) Bennu indicative of a rubble pile with internal stiffness (Nature Geoscience, (2019), 12, 4, (247-252), 10.1038/s41561-019-0330-x)
Nature Geoscience 13:11 (2020) 764
Abstract:© 2020, The Author(s), under exclusive licence to Springer Nature Limited. An amendment to this paper has been published and can be accessed via a link at the top of the paper.
Studying the composition and mineralogy of the hermean surface with the Mercury Radiometer and Thermal Infrared Spectrometer (MERTIS) for the BepiColombo mission: an update
Space Science Reviews Springer 216:6 (2020) 110