View Full Version : Is Phoebe a comet?

2004-Jun-14, 04:01 PM
Saturn's moon reveals violent past (http://www.newscientist.com/news/news.jsp?id=ns99995106)

The new pictures show that most of the moon is dark, but impacts have blasted holes in the surface to reveal much brighter material underneath, which is probably a mixture of ices. So Phoebe looks like a dirty snowball - the term coined to describe comets.

2004-Jun-14, 04:39 PM
There are four outer moonlets, less than 10 km across, that have similar orbits to Phoebe. When they were discovered in 2001, scientists suggested they might have been chipped off the moon by violent impacts. If so, they predicted that the impacts would have blasted out huge craters 50 km across - and now Cassini's images have borne that prediction out.

Sounds like the explanation for Iapetus's mysterious appearance is becoming more plausible.

2004-Jun-14, 08:16 PM
Wouldnt it probably be more plausible that its a captured asteroid though? Several have orbits beyond Saturn.

2004-Jun-14, 09:36 PM
In my personal opinion ('cause I've never heard this in any books/papers), there is a blurred line between asteroids and comets. Asteroids are generally rocky bodies that orbit between Jupiter and Mars, and comets are transient icy bodies that produce lovely comas and tails when they get inside about 5 A.U.

But what about small bodies between Jupiter and the Kuiper belt -- is there some imaginary line where something becomes a comet once it has enough ice?

Anyway, I guess that's just food for thought when asking if Phoebe is a comet vs asteroid. Let's just say it's a moon and leave it. 8)

Donnie B.
2004-Jun-15, 12:48 PM
Is Phoebe a comet?

In the immortal words of Inspector Clouseau: "Not any more!"

2004-Jun-15, 04:12 PM
Saturn's Moon Phoebe: Old, Beaten and Still Mysterious (http://www.space.com/scienceastronomy/phoebe_unveiled_040615.html)

And if preliminary analyses of new images are correct, this tiny moon of Saturn is quite the wanderer, a vagabond of the frigid fringes of the solar system that's been lured inward, grabbed by Saturn's mighty gravity, and turned into an awkward satellite.