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Spectral Behavior of Hematite at Visible/Near Infrared and Midinfrared WavelengthsThe oxide mineral hematite alpha-Fe2O3) is present on Mars as evidenced by spectroscopy using visible/near infrared (VNIR) and midinfrared (MIR) wavelengths. The physical nature of this surficial hematite varies from fine-grained, crystalline red hematite (red-Hm) in certain martian bright regions, to coarser-grained, crystalline gray hematite (gray-Hm) in the Sinus Meridiani equatorial site discovered in the Mars Global Surveyor Thermal Emission Spectrometer (MGS-TES) data. The VNIR spectra require that the red hematite is present in amounts subordinate to a second ferric pigment, which accounts for the general shape and position of the martian ferric absorption edge. By analogy with palagonitic tephra and synthetic samples, the pigment is a nanophase ferric oxide, possibly nanophase hematite (np-Hm). The purpose of this abstract is to document the physicospectral properties of hematite in the VNIR (0.35 to 2.2 microns) and MIR (5 to 25 microns) with respect to the terms "nanophase" and "crystalline", "red" and "gray", and "fine-grained" and "coarse-grained". We will show that different "types" of hematite (no-, red-, and gray-Hm) have different spectral responses in the VNIR and MIR regions and that these differences are important for inferring the types of hematite and their relative proportions from remotely sensed spectra of Mars. Because hematite is an alteration product that forms through many different geologic processes, determination of the type of hematite provides important clues about the style and diversity of martian weathering processes.
Document ID
20000094537
Acquisition Source
Johnson Space Center
Document Type
Preprint (Draft being sent to journal)
Authors
Lane, Melissa D.
(NASA Johnson Space Center Houston, TX United States)
Christensen, Philip R.
(Arizona State Univ. AZ United States)
Date Acquired
August 19, 2013
Publication Date
January 1, 1999
Subject Category
Geophysics
Meeting Information
Meeting: Mars
Location: Pasadena, CA
Country: United States
Start Date: July 18, 1999
End Date: July 23, 1999
Sponsors: California Inst. of Tech.
Funding Number(s)
PROJECT: RTOP 344-31-00
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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