Spectral properties of Martian and other planetary glasses and their detection in remotely sensed data

• Published in: Journal of geophysical research. Planets 2017-01, Vol.122 (1), p.249-268
• Main Authors: Cannon, Kevin M., Mustard, John F., Parman, Stephen W., Sklute, Elizabeth C., Dyar, M. Darby, Cooper, Reid F.
• Format: Article
• Language: English
• Subjects: Absorption; Absorption spectra; Albedo; Analogs; Coherence; Datasets; Deposits; Geophysics; Glass; Infrared spectra; Infrared spectroscopy; Iron content; Libraries; Mars; Mars (planet); Mars satellites; Mars surface; Mars volcanoes; Mathematical models; Mercury; Moon; Oxygen; Pixels; Planet detection; Remote sensing; Spectra; spectrocopy; Spectroscopic analysis; Spectroscopy
• ISSN: 2169-9097; 2169-9100
• DOI: 10.1002/2016JE005219

Thirty silicate glasses were synthesized as realistic analogs to those expected to exist on Mars, the Moon, and Mercury. Samples were measured using visible/near‐infrared and Mössbauer spectroscopy to determine the effects of varying bulk chemistry, oxygen fugacity, and temperature on spectral properties. For Martian glasses, the fO2 during fusion strongly affects absorption band intensities in the spectra, while bulk chemistry has noticeable secondary effects on absorption band positions. Titanium and iron content drive spectral changes in lunar glasses, where Fe3+ is effectively absent. Iron‐free Mercury analog glasses have much higher albedos than all other samples, and their spectral shape is a close match to some pyroclastic deposits on Mercury. Synthetic glass spectra were used as inputs into a spectral unmixing model applied to remote orbital datasets to test for the presence of glass. The model is validated against physical laboratory mixture spectra, as well as previous detections of glass‐rich pyroclastic deposits on the Moon. Remote data were then used from suspected impact deposits and possible pyroclastic deposits on Mars as a new application of the model: the results reveal spatially coherent glass‐rich material, and the strong spectral match of the synthetic glasses to these remotely sensed data gives new insights into the presence and character of glasses on the Martian surface. The large library of glass spectra generated here, acquired from consistently synthesized and measured samples, can serve as a resource for further studies of volcanic and impact processes on planetary bodies. Key Points Visible/near‐infrared spectral properties are examined for a wide range of synthetic planetary glasses A spectral mixing model is described to detect the presence of glass in mixed pixels Using the spectral mixing model, glasses are identified in both impact and volcanic settings on Mars