Planetary surfaces

Abstract:

New laboratory thermal infrared emissivity measurements of the plagioclase solid solution series over the 1700∼400cm-1 (6-25m) spectral range are presented. Thermal infrared (TIR) spectral changes for fine-particulate samples (0-25m) are characterized for the first time under different laboratory environmental conditions: ambient (terrestrial-like), half-vacuum (Mars-like), vacuum, and vacuum with cooled chamber (lunar-like). Under all environmental conditions the Christiansen Feature (CF) is observed to vary in a systematic way with Na-rich end-member (albite) having a CF position at the highest wave number (shortest wavelength) and the Ca-rich end-member (anorthite) having a CF position with the lowest wave number (longest wavelength). As pressure decreases to<10-3mbar four observations are made: (1) the CF position shifts to higher wave numbers, (2) the spectral contrast of the CF increases relative to the RB, (3) the spectral contrast of the RB in the ∼1200-900 spectral range decreases while the spectral contrast of the RB in the ∼800-400 spectral range either increases or remains the same and (4) the TF disappears. A relationship between the wavelength position of the CF measured under simulated lunar conditions and plagioclase composition (An#) is developed. Although its exact form may evolve with additional data, this linear relationship should be applied to current and future TIR data sets of the Moon. Our new spectral measurements demonstrate how sensitive thermal infrared emissivity spectra of plagioclase feldspars are to the environmental conditions under which they are measured and provide important constraints for interpreting current and future thermal infrared data sets. © 2012 American Geophysical Union. All Rights Reserved.

Abstract:

We present new laboratory thermal infrared emissivity spectra of the major silicate minerals identified on the Moon measured under lunar environmental conditions and evaluate their application to lunar remote sensing data sets. Thermal infrared spectral changes between ambient and lunar environmental conditions are characterized for the first time over the 400∼1700 cm -1 (6-25 m) spectral range for a fine-particulate mineral suite including plagioclase (albite and anorthite), pyroxene (enstatite and augite), and olivine (forsterite). The lunar environment introduces observable effects in thermal infrared emissivity spectra of fine particulate minerals, which include: (1) a shift in the Christiansen feature (CF) position to higher wave numbers (shorter wavelengths), (2) an increase in the overall spectral contrast, and (3) decreases in the spectral contrast of the reststrahlen bands and transparency features. Our new measurements demonstrate the high sensitivity of thermal infrared emissivity spectra to environmental conditions under which they are measured and provide important constraints for interpreting new thermal infrared data sets of the Moon, including the Diviner Lunar Radiometer Experiment onboard NASA's Lunar Reconnaissance Orbiter. Full resolution laboratory mineral spectra convolved to Diviner's three spectral channels show that spectral shape, CF position and band ratios can be used to distinguish between individual mineral groups and lunar lithologies. The integration of the thermal infrared CF position with near infrared spectral parameters allows for robust mineralogical identifications and provides a framework for future integrations of data sets across two different wavelength regimes. Copyright 2012 by the American Geophysical Union.

Abstract:

We describe a stratospheric balloon mission that will make continuous observations of Venus over a period of several weeks during the January 2014 inferior conjunction. NASA's balloon program has historically supported Antarctic flights like this one in the eliophysics and Astrophysics Divisions. The proposed experiment consists of a one meter telescope, two imaging detectors operating from 0.35 to 2.55 ! m at the diffraction limit and 33 filters. This mission will address a number of questions regarding (a) Venus' super-rotation and general circulation, (b) the properties of Venus' clouds, (c) the distribution of trace species and the coupling between certain dynamical and chemical processes, (d) the existence and prevalence of lightning on Venus, and (e) the distribution of thermal emissivity anomalies on Venus' surface. We call this mission VSS (Venus StratoScope) to keep in mind the legacy of the Stratoscope and Stratoscope II balloon missions.