Paper No. 4
Presentation Time: 2:15 PM
WIDESPREAD EXPLOSIVE VOLCANISM ON MARS INFERRED FROM THE GLOBAL DISTRIBUTION OF GLASS-RICH SEDIMENTS (Invited Presentation)
HORGAN, Briony1, CHOJNACKI, Matthew2, LAI, Jason3, CLARKE, Danielle3, JOSEPH, Jonathan4 and BELL III, James F.5, (1)EAPS Department, Purdue University, West Lafayette, IN 47907, (2)Department of Earth and Planetary Sciences, University of Tennessee, Knoxville, TN 37996, (3)School of Earth and Space Exploration, Arizona State University, Phoenix, AZ 85287, (4)Center for Radiophysics and Space Research, Cornell University, Ithaca, NY 14853, (5)School of Earth & Space Exploration, Arizona State University, P.O. Box 871404, Tempe, AZ 85287, briony@purdue.edu
Weathered iron-bearing glass has been identified as the primary phase in over ten million square kilometers of low-albedo deposits in the northern lowlands of Mars, based on visible to near-infrared (0.36–2.5 μm) spectra from the OMEGA imaging spectrometer onboard Mars Express. The glass exhibits a concave blue slope in the near-infrared that is consistent with a leached glass rind. This rind is formed during exposure of glass to at least slightly acidic fluids under water-limited conditions, and is commonly observed in dry volcanic environments on Earth. The proposed origin for these materials is explosive volcanism, potentially triggered due to ice-magma interactions in the late Hesperian or Amazonian, followed by post-depositional acidic weathering at the surface. A possible analog for these glass-rich sedimentary terrains are the extensive sand plains, dune fields, and flood plains of Iceland, which are composed of glass-rich (50-90%) volcaniclastic sediments formed during sub-glacial eruptions. The large scale of the martian deposits suggests widespread (and potentially ice-related) explosive volcanism either in the northern lowlands or near the dichotomy boundary. This possibility raises the question: How widespread are glass-rich deposits on Mars globally?
To address this question, we have developed a global set of visible/near-infrared OMEGA mosaics at 1 km/pixel resolution. Preliminary analysis of this data set indicates that the concave spectral slope that we associate with weathered glass is present in large portions of the Syrtis Major region and in several dozen dune fields in the regions of Arabia Terra, Valles Marineris, and the Argyre Basin. Higher resolution CRISM observations of several Valles Marineris dune fields appear to confirm these results, as their spectra are consistent with iron-bearing glass. We are currently working to extend this analysis globally, and to search for correlations with mid-infrared compositions from TES, sediment sources, and predicted distributions of pyroclastic deposits from the major volcanic edifices. However, even these preliminary results strongly suggest that weathered glass is a major component of global martian sediments, and that explosive volcanism has played an important role in shaping the martian surface through time.
