291-12 Analyzing Patterns in Morphology and Mineralogy of Interdunes at Olympia Undae, Mars

Session: Mineralogy in the Solar System

Presenting Author:

Dora Elalaoui-Pinedo

Authors:

Elalaoui-Pinedo, Dora¹, Bishop, Janice L.², Fenton, Lori K.³, Gruendler, Markus R. D.⁴, Itoh, Yuki⁵, Yanez, Katya L.⁶, Parente, Mario⁷, Szynkiewicz, Ania⁸, Zuschneid, Wilhelm⁹, Gross, Christoph¹⁰, Gibson, Tatiana¹¹

(1) SETI Institute, Mountain View, CA, USA; University of Arizona, Tucson, AZ, USA, (2) SETI Institute, Mountain View, CA, USA, (3) SETI Institute, Mountain View, CA, USA, (4) SETI Institute, Mountain View, CA, USA; University of California San Diego, La Jolla, CA, USA, (5) University of Massachusetts Amherst, Amherst, MA, USA, (6) SETI Institute, Mountain View, CA, USA; Brown University, Providence, RI, USA, (7) University of Massachusetts Amherst, Amherst, MA, USA, (8) University of Tennessee, Knoxville, TN, USA, (9) Freie Universität Berlin, Berlin, Germany, (10) Freie Universität Berlin, Berlin, Germany, (11) Georgia Institute of Technology, Atlanta, GA, ,

Abstract:

Olympia Undae is the largest dune field on Mars, partly encircling Planum Boreum, the north polar ice cap. Uniquely, its dark dunes contain a substantial fraction of gypsum, unlike most Martian dunes, which consist of basalt. Gypsum is typically found in ancient Martian terrains (>3.7 Ga), so its presence in these young dunes (<300 Ma) is puzzling. The dunes are also intriguing due to bright-toned material observed between the dunes that likely represents the underlying basal unit. Our study characterizes morphological and mineralogical differences of these interdunes across Olympia Undae to understand the character and origins of the gypsum and associated salts, as interdunes may preserve exposed materials and formation processes distinct from the dunes.

 

We analyzed 5 hyperspectral images from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) that were processed to minimize atmospheric components and reduce noise, spanning 1-2.65 μm. We used High Resolution Imaging Science Experiment (HiRISE) images to catalog overlapping CRISM and HiRISE coverage. Using JMARS, a geospatial information system, we mapped and categorized interdune morphologies into four types: megaripples (~5-40 m spacing); light polygonal terrain (relatively bright, fractured terrain, ~0.5-3 m polygons); dark polygonal terrain (relatively dark, fractured terrain, ~3-10 m polygons); and intermixed polygonal terrain (relatively bright, fractured terrain ~2-5 m polygons with overlying dune-derived sand). We collected interdune spectra from each morphological category at 1×1 pixel resolution (18 m/px) using ENVI, a hyperspectral image analysis tool.

 

Current findings demonstrate strong gypsum absorption bands in megaripples and light polygonal terrain within eastern interdunes, consistent with the gypsum composition of surrounding dunes. In contrast, spectra of intermixed polygonal terrain in western interdunes exhibit weak gypsum signatures and different spectral features, consistent with rozenite or other hydrated iron sulfates. These features are indicated by a strong ferrous iron slope from 1.0-1.6 μm and a shift in the hydrated sulfate feature from 2.48 μm (gypsum) to 2.53 μm (rozenite). Additionally, polygonal cracking within interdunes suggests a past evaporite deposit, with evidence of secondary salt precipitation. Studying interdunes within Olympia Undae's gypsum-bearing dunes offers insight into aqueous processes in the northern circumpolar region, including the possible presence of additional evaporite minerals, and advances our understanding of the climate history on Mars and present-day polar processes.

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