FIELD HYPERSPECTRAL VISIBLE IMAGING SPECTROSCOPY OF SERPENTINE DEPOSITS IN QUEBEC: IMPLICATIONS FOR THE VALUE OF VISIBLE SPECTROSCOPY IN PLANETARY EXPLORATION

Visible-near infrared (VNIR) imaging systems provide the first compositional information for landed science investigations (e.g. Pancam on the Mars Exploration Rovers, Mastcam on the Mars Science Laboratory), and imaging spectroscopy is contemplated for future lunar and martian rovers. Coordinated field investigations of analog terrains using hyperspectral imaging systems are an essential step toward documenting the link between VNIR data and lithology, mineralogy, and processes and for guiding future rover operations.

An abandoned chrysotile mine in Norbestos, Quebec, was the site of the Canadian Space Agency’s Mars Methane Analog Mission deployment and was investigated to assess technologies to detect and characterize methane produced by serpentinization. The outcrop lithologies are dominated by serpentine and are part of the Appalachian ophiolites.

Samples were collected and imaged in the field with a hyperspectral imager from 420 to 720 nm with 5 nm sampling and calibrated to approximate reflectance using calibration targets within the images. Exposed walls of the mine were also imaged, and samples from within the images were collected for validation. Together, the set of images and samples are being used to relate serpentinization and alteration processes to their spectroscopic signatures at the rover and hand-sample scale and connect the samples and wall rocks. We use laboratory measurements of the samples with an ASD point spectrometer from 350 to 2500 nm to assess the relationship between VNIR and infrared spectra. Additional laboratory analyses are underway to characterize chemistries and mineralogies. Visible imaging data are indicative of Fe mineralogy and are dominated by crystal field and charge transfer absorptions of Fe. Variability within and across samples and images are due to both different serpentine minerals and oxidative weathering of serpentine. We can trace oxidation across surfaces and are working to resolve the nature and spectral characteristics of the oxidation. Samples also show variability in ASD infrared spectra, which are dominated by overtones and combination tones of serpentine minerals but show differences in mineralogy and expression of H₂O. We will present results showing how these technologies resolve geologic processes and can be used in an exploration context.