Actions for Characterization of the Morphometry of Impact Craters Hosting Polar Deposits in Mercury's North Polar Region

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Characterization of the Morphometry of Impact Craters Hosting Polar Deposits in Mercury's North Polar Region

Author
Solomon, Sean C.
Published
March 19, 2012.
Physical Description
1 electronic document
Additional Creators
Neumann, Gregory A., Talpe, Matthieu, J., Zuber, Maria T., Vilas, Faith, 1952-, and Mazarico, Erwan
Online Version

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Summary
Earth-based radar images dating back two decades show that the floors of some polar craters on Mercury host radar-bright deposits that have been proposed to consist of frozen volatiles. Several hypotheses have been put forth to explain their source, including volcanic outgassing, chemical sputtering, and deposition of exogenous water ice. Calculations show that volatiles are thermally stable in permanently shadowed areas. An earlier study of the depths of north polar craters determined with photoclinometric techniques applied to Mariner 10 images yielded the conclusion that the mean ratio of crater depth d to rim-crest diameter D for craters hosting polar deposits is two-thirds that of the mean ratio for a comparable population of neighboring craters lacking such deposits. This result could be explained by (though doesn't require) the presence of a thick layer of volatiles within the polar deposit-hosting craters. Here we use altimetric profiles and topographic maps obtained by the Mercury Laser Altimeter (MLA) to revisit this analysis. MLA is an instrument on the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft, which has been orbiting Mercury since March 2011. MLA transmits a 1064-nm laser pulse at 8 Hz during MESSENGER's trajectory over Mercury s surface. The MLA illuminates surface areas averaging between 15 m and 100 m in diameter, spaced approx 400 m apart along the spacecraft ground track. The radial precision of individual measurements is <1 m, and the current accuracy with respect to Mercury s center of mass is better than 20 m. As of mid-December 2011, MLA coverage had reached to 15 S and has yielded a comprehensive map of the topography of Mercury s northern hemisphere. The MLA data are used here to quantify the shapes of craters in the north polar region and to avoid the shadowing bias of photoclinometric techniques.
Other Subject(s)
Collection
NASA Technical Reports Server (NTRS) Collection.
Note
Document ID: 20120009642.
GSFC.CP.00109.2012.
43rd Lunar Planetary Science Conference; 19-23 Mar. 2012; Woodlands, TX; United States.
Terms of Use and Reproduction
Copyright, Distribution as joint owner in the copyright.
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