Mass Anomalies on Ganymede

Details Mass Anomalies on Ganymede Mass Anomalies on Ganymede

Dec 2004

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2004agufm.p31a0967p&link_type=abstract

American Geophysical Union, Fall Meeting 2004, abstract #P31A-0967

Other

6062 Satellites, 6218 Jovian Satellites

Scientific paper

The discovery of mass anomalies on Ganymede was reported this summer (Anderson et al., Science 305, 989 (2004)). We report here on a more detailed characterization of the source of the anomalies. In order to reduce the noise evident in the Doppler residuals previously used, we applied a variable-width Gaussian filter to the time series. The filter width in the time domain increases with the spacecraft altitude, reducing the noise before and after closest approach. The smoothed Doppler data were numerically differentiated and the resulting accelerations along the line of sight were fit with a multiple point-mass model. The variable-width filter reveals a previously obscured positive acceleration feature about 300 s before closest approach. Rather than two or three mass points as reported in Anderson et al., we find that five mass points provide a much improved fit to the data, including the new acceleration feature before closest approach. Two of the five masses are near the previous masses from the two-point fit, and are in good agreement with their mass values. There is a positive anomaly at about 60o north latitude and a negative anomaly at about 24o north latitude. We conclude that the two-point fit reveals two major anomalies on Ganymede, but misses three more revealed by the five-point fit. Further, the mass anomalies can be divided into two groups. Three of the five masses could indicate a single broad anomaly under the outgoing flyby trajectory centered roughly at 45o north latitude and 18o west longitude. The other two masses could indicate a single extended anomaly under the incoming trajectory centered roughly at 20o north latitude and 173o west longitude. We also include results on placing the five masses at different depths from zero to 1450 km below the surface. A good fit is obtained at any depth from surface to rock-ice interface at about 800 km depth, but the fit deteriorates at greater depth. It is highly unlikely mass anomalies exist within Ganymede's ice shell. We prefer either the near surface or the rock-ice interface. The rock-ice interface is attractive based on rigidity arguments, and the suggestion of two major extended anomalies is even more striking at greater depth. In order to fit the acceleration data, the anomalies must be six or seven times more massive at the 800 km depth than at the surface.

Affiliated with

Also associated with

No associations

Rating

Mass Anomalies on Ganymede does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Mass Anomalies on Ganymede, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Mass Anomalies on Ganymede will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-1452993