Hi All

Here's an abstract from an American Astronomical Society meeting...

[5.07] The Orbits of the Major Saturnian Satellites and the Gravity Field of the Saturnian System
R. A. Jacobson, P. G. Antreasian, J. J. Bordi, K. E. Criddle, R. Ionasescu, J. B. Jones, R. A. Mackenzie, M. C. Meek, F. J. Pelletier, D. C. Roth, I. M. Roundhill, J. R. Stauch (JPL/Caltech)

...just the title since there's no point duplicating it for my purposes, chiefly pointing out the new GM value for Enceladus = 7.205 ± 0.017. This indicates a mass within the error bars on the previous best estimate, GM = 7.88 ± 0.75, and a density of ~ 1.673 ± 0.002. This is a lot higher than dynamical studies of its oblateness and other lines of evidence have suggested, including theoretical values from Andrew Prentice's Modern Laplacian Theory (~ 1.00.) Possibly Enceladus had a large volatile fraction, say CH4, and this has been totally lost to space leaving a 50/50 ice/rock mix. Or Enceladus has a relatively low water ice fraction and a lot more ammonia - as indicated by recent spectroscopy. That would drive up the rock fraction even more perhaps leading to a lot more chondritic heating as the cause of Enceladus' extensive cryovolcanism.

Adam