View Full Version : Discussion: Amalthea is Just a Pile of Icy Rubble

2005-Jun-01, 04:58 PM
SUMMARY: By studying data gathered by NASA's Galileo spacecraft, researchers have come to the conclusion that Amalthea, one of Jupiter's moons, is probably just a jumble of icy rubble, held together by gravity. Scientists originally believed it was made of rock, but Galileo helped to discover that its density is actually lower than water. It probably formed further out in the solar system, but was then captured into a stable orbit by Jupiter's immense gravity.

View full article (http://www.universetoday.com/am/publish/amalthea_pile_rubble.html)

What do you think about this story? Post your comments below.

2005-Jun-01, 05:58 PM
I'd expect that since Amalthea is so close to Jupiter (so deep in it's gravity well) that just about every small asteroid that collides with it will have relatively extreme velocity. This should tend to keep the moon as a gravitationally bound bag of gravel.

2005-Jun-02, 02:24 AM
I agree with the theory that this is a captured object. It's icy characteristics and reddish hue suggest it spent some time wandering the outer solar system before arriving in its current orbit. Since it got too close to Jupiter, its tidal forces ripped it apart, leaving it a pile of rubble.

2005-Jun-02, 08:37 AM
The obvious question if we look at Amalthea's surface features is how such a supposed pile of icy rubble can support such a large crater. Why don't we hear more about how unlikely such features are, and how this moon looks more like an asteroid, just like Saturn's Phoebe.


2005-Jun-02, 11:37 AM
As I recall, Saturn itself would float in water, i.e., it has a density lower than water.

Some pumice (volcanic rock) has a low overall density.

Styrofoam has an even lower overall density.

The question is how tightly the material is compacted together.

Saturn is huge so there is little doubt it is made of light elements like H and He.

Amalthea may be made of light elements, too.

Or it may be loosely compacted, like pumice and styrofoam.

With kind regards,


2005-Jul-06, 05:09 AM
Maby it is a huge ball of ice and snow like a comet.