is a valley on Saturn
's moon Tethys
, named after the island of Ithaca
, in Greece
. It is 100 km wide, 3 to 5 km deep and 2,000 km long, running approximately three-quarters of the way around Tethys' circumference. Ithaca Chasma is approximately concentric with Odysseus crater
The chasma has a rather complex structure, being made of multiple parallel scarp
. Its width varies from only a few kilometers at some places to more than 100 km.
It is thought that Ithaca Chasma formed as Tethys' internal liquid water solidified, causing the moon to expand and cracking its surface to accommodate the extra volume within. Earlier crater
made before Tethys solidified were probably all erased by geological activity before then.
Tethys' subsurface ocean may have resulted from a 2:3 orbital resonance
between Dione and Tethys early in the solar system's history. The resonance would have led to orbital eccentricity
and tidal heating
that may have warmed Tethys' interior enough to form the ocean. Subsequent freezing of the... Read More