Constraints on the Location, Magnitude, and Dimensions of Ganymede's Mass Anomalies

Details Constraints on the Location, Magnitude, and Dimensions of Ganymede's Mass Anomalies Constraints on the Location, Magnitude, and Dimensions of Ganymede's Mass Anomalies

Dec 2008

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008agufm.p23a1360p&link_type=abstract

American Geophysical Union, Fall Meeting 2008, abstract #P23A-1360

Physics

6218 Jovian Satellites, 6222 Ganymede

Scientific paper

Previously, radio Doppler data, generated with NASA's Galileo spacecraft, were utilized to infer the locations and magnitudes of mass anomalies on the satellite. These earlier models used point masses to fit the line- of-sight acceleration obtained from the Doppler data. However, the point-mass solutions cannot provide the vertical and horizontal extent of the anomalous mass concentrations. We report here on a new study using spherical cap disks to model Ganymede's mass anomalies. The spherical cap disk models not only provide the locations and magnitudes of the mass anomalies, but also their vertical and horizontal dimensions. Although four or five point masses were required to fit the line-of-sight acceleration data, our new models show that three disks can reproduce all the major acceleration features. The three-disk solution results in a positive mass anomaly in Galileo Regio (53.0° N, 127.0° W) and two negative mass anomalies in the bright terrain on either side of the regio at (22.0° N, 87.0° W) and (49.0° N, 219.0° W). The magnitudes of these mass anomalies are on the order of 1018 kg and the diameters are a few thousand kilometers. The positive anomaly is about 100 meters thick and both negative anomalies have a thickness of less than a kilometer. Additionally, we explore the viability of mass anomalies at the satellite's surface using the new information provided by the disk models to make a comparison between the sizes of the anomalies and the regions of dark and bright terrain on Ganymede. We find that the dimensions of the mass anomalies likely can be explained by concentrations of rock in Galileo Regio and rock-free ice in the sulci. These results confirm that mass anomalies may reside on or near Ganymede's surface and that positive mass anomalies are correlated to areas of dark terrain and negative mass anomalies to areas of bright terrain.

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