Amalthea And Company Options

[Tayfun Öner]

Phil,

I once saw renderings of Metis, Thebe and Amalthea from 3d models, probably by Peter Thomas. Do you know if they are available somewhere?

[Phil Stooke]

Hi - I don't recall ever seeing these. Are you thinking of one of the commercial products like the Dorling Kindersley Eyewitness Atlas of the Solar System? I think they have animated renderings, maybe not of Metis, though.

Somewhere I have a shape model for Thebe, not very good though, and certainly one of Amalthea, which is on the PDS Small Body Node.

Phil.

[Tayfun Öner]

Hi Phil, I found the image, it was originally in the Galileo website:

http://rhein-zeitung.de/on/98/09/16/topnews/jupiter.jpg

[Guest_BruceMoomaw_*]

One interesting abstract from last year's LPSC on Galileo's gravity-field measurements of Amalthea during its close flyby: http://www.lpi.usra.edu/meetings/lpsc2005/pdf/1279.pdf . They weren't able to establish a 2-way transponder link during the flyby as they had hoped, and had to settle for a somewhat less sensitive 1-way link -- but the abstract says that in the end this may not have made much difference:

"GALILEO made its final experiment of its successful mission on November 5, 2002: a close Amalthea flyby. The spacecraft’s state vector (radius, velocity) at closest approach and the gravity models of Amalthea have been integrated and various spacecraft trajectories around closest approach have been calculated. Because of the moon’s low density of about 860 kg/cubic meter, no information about the quadrupole or higher degree moments of gravitation could be derived. Thus no analysis of Amalthea’s interior could be made from this specific flyby. Predictions for future flyby scenarios show that not even a closer flyby would generate a much higher gravity signal, which implies that other means like in-situ geological measurements are needed to get information about the moon’s interior structure."

One interesting thing jumps out at me from this passage: that 0.86 g/cc density for Amalthea. We were told after the Galileo flyby that this proved that Amalthea was not only a rubble pile, but one that must be made of ice. But the innermost moons of Saturn -- rubble piles made of ice -- have been measured by Cassini as having densities as low as 0.36 to 0.5 g/cc, and Janus and Epimetheus are only about 0.65 to 0.7 g/cc ( http://www.lpi.usra.edu/meetings/lpsc2006/pdf/2289.pdf ). Is it possible, given Amalthea's higher density, that it may be a loose rubble pile made out of rock after all?