A Search For Carbon In Mercury's Surface Material From Mariner 10 EUV Data
Abstract
Carbon, as graphite, emerged from analyses of Mercury MESSENGER spectrophotometry and theoretical modeling as a possible source for the darkening component in the Low Reflectance Material (LRM), pervasive across Mercury's equatorial surface. Based on the presence of a 600-nm absorption in the Mercury Dual Imaging System (MDIS) photometry, graphite in amounts consistent with the results from MESSENGER's elemental experiments for the presence of C was proposed as the most likely darkening component in LRM. Two general theories about the origin of the carbon have been proposed. In one scenario, graphite would be the only buoyant phase in an early magma ocean, and any primary flotation crust would have retained C in the form of graphite. Carbon from cometary sources has also been proposed to be the darkening material. Alternatively, nanophase and microphase iron (rather than C), produced by impacts into Mercury's crust before and during the late heavy bombardment, could darken the LRM. Graphitized carbon has distinctive far-UV spectral reflectance features that change with the level of graphitization. The MESSENGER Mercury Atmospheric and Surface Composition Spectrometer (MASCS) Ultraviolet and Visible Spectrometer (UVVS) did not extend to wavelengths low enough to observe these features. We are re-analyzing Mariner 10 Extreme Ultraviolet (EUV) airglow spectrometer data in a search for this distinctive UV signature of graphitized carbon across large areas of Mercury's surface. The spectrometer observed broad swaths of Mercury's surface during Fly-bys 1 (29 Mar 1974) and 3 (16 Mar 1975). One observation set includes counts through 10 filters at the wavelengths 304, 430, 580, 740, 869, 1048, 1216, 1304, 1480, 1659 Å, each having 20Å passbands. A slit cutting across the disk in one direction was stepped across the visible portion of the planet's disk. We have uncovered ~880 individual sets of photometry covering all or part of Mercury's surface. For each observation, we are projecting the slits onto the MESSENGER high-resolution (~665m/pixel) global color mosaic of Mercury, to view the surface area covered by the slit during the observation and derive the corresponding visible photometry. For each observation, we also expect to produce corrected I/F values in each filter.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMP014.0004J
- Keywords:
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- 6008 Composition;
- PLANETARY SCIENCES: COMETS AND SMALL BODIES;
- 6025 Interactions with solar wind plasma and fields;
- PLANETARY SCIENCES: COMETS AND SMALL BODIES;
- 6205 Asteroids;
- PLANETARY SCIENCES: SOLAR SYSTEM OBJECTS;
- 5410 Composition;
- PLANETARY SCIENCES: SOLID SURFACE PLANETS