Ithaca Chasma

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Ithaca Chasma is a valley on Saturn's moon Tethys. It is 100 km wide, 3 to 5 km deep and 2,000 km long, running approximately three-fourths of the way around Tethys' circumference. It is named after the island of Ithaca, in Greece.

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 craters 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 ocean after the moons escaped from the resonance may have generated the extensional stresses that created Ithaca Chasma.^[1][2]

An alternative theory is that it was formed at the same time as the large crater Odysseus which is on the opposite side of the moon. When the impact that created Odysseus occurred, the shockwave may have traveled through Tethys and fractured the icy, brittle surface on the other side.

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