Celestia Forums

This picture shows Mimas's oblateness.
http://saturn.jpl.nasa.gov/multimedia/images/raw/raw-images-details.cfm?feiImageID=40563

Wikipedia has the same picture and said that the long axis is 10% longer than the short one, which I also got with measurements of the picture.

The mean radius is 298.6 km, so is this ok to do?

Long axis radius = 298.6 * 1.05
Short axis radius = 298.6 * 0.95

Oblateness = (long - short) / long = 0.09524



I did measurements on an image of Mimas from Celestia using that oblateness and got the same result as I did from the Cassini image.

I am not sure you can take that picture at face value. There apears to be a distinct shadow line on the one side and that would the Mimas in a gibous phase in this picture and not even full on forward view. So where posibly could these numbers be coming from?

Don.

I found something about Mimas's shape here. http://www.shatters.net/forum/viewtopic.php?t=6572&highlight=oblateness+mimas

Won't Mimas's long axis be pointed at Saturn? The oblateness parameter makes it oblate all the way around.

I am no full fledged astonomer, pre-amature at best, but if Mimas was knocked with an asteroid big enough to create that Death Star appearance, I would venture that it became semi molten late in the game. Enough to reform with Saturn's gravity tugging on it. I think Iapetus is far cooler, maybe it even split in half and reformed causing that equatorial ridge. The impact basin on Iapetus is 3 times this size of Mimas'...

http://antwrp.gsfc.nasa.gov/apod/ap050201.html

Mimas is actually a triaxial ellipsoiid. A simple oblateness assumption would lead to some things that have trouble matching.