The solar system's weirdest moon once had a moon all its own

[Swede]

Saturn's moon Iapetus has a gigantic ridge running along its equator that's twice the height of Mount Everest and covers 75% of the moon's equator. And its existence points to something stranger still: Iapetus once had its very own moon.

You can always know immediately when you're looking at an image of Iapetus, because it's the moon that looks like a giant walnut hanging in space. The bizarre equatorial ridge that creates that effect is staggeringly huge: it's a couple thousand kilometers long, and up to 100 kilometers wide and 20 kilometers tall. So where did it come from?

http://io9.com/5713479/the-solar-systems-weirdest-moon-once-had-a-moon-all-its-own

[krispos42]

1. Neat! I'm starting to think that Saturn's system is far and above...

...the most interesting in the Sol System.

Maybe Author C. Clarke was right when he had 2010: A Space Oddessy wandering around Saturn instead of Jupiter.

[Nihil]

2. I like that explanation.

I've always been fascinated with Iapetus ever since seeing the early
photos of it.

Thanks for posting that! :hi:

[dimbear]

3. If cracked open on the seam, does it contain

toys or candy?

Seriously, since the earth's moon is scheduled to come back home in the future, we'll look just like that too, eh?

[Systematic Chaos]

4. I thought our Moon was slowly moving away....

I think I read somewhere that total solar eclipses would become impossible millions of years from now.

Hmmm.... :shrug:

[dimbear]

5. You are correct. Moving away now and scheduled to return much later.

It's all up to tidal forces, which are spinning the moon farther away now, and then the whole system will gradually slow down and come back together as the earth slows down its own spin. At least that's the theory I learned. At any rate, this won't happen for several more years. Well, several billion more years. :)