# Tethys

Saturn III

Tethys [TEE-this] was discovered by Giovanni Cassini in 1684. It is an icy body similar in nature to Dione and Rhea. The density of Tethys is 1.21 gm/cm3, indicating that it is composed almost entirely of water-ice. Tethys's icy surface is heavily cratered and contains cracks caused by faults in the ice. There is one enormous trench on Tethys about 65 kilometers (40 miles) wide and extending from above the center to the extreme left. It covers three-fourths of Tethys' circumference. The fissure is about the size scientists would predict if Tethys were once fluid and its crust hardened before the interior. The canyon has been named Ithaca Chasma. A vast expanse of relative young plains also exists on Tethys. Tethys' surface temperature is -187° C (-305° F).

## Tethys Statistics

    Discovered by ..................... Giovanni Domenico Cassini
    Date of discovery ...................................... 1684

    Mass (kg) .......................................... 7.55e+20
    Mass (Earth = 1) ................................. 1.2634e-04
    Equatorial radius (km) .................................. 530
    Equatorial radius (Earth = 1) .................... 8.3098e-02
    Mean density (gm/cm^3) ................................. 1.21

    Mean distance from Saturn (km) ...................... 294,660
    Rotational period (days) ........................... 1.887802
    Orbital period (days) .............................. 1.887802
    Mean orbital velocity (km/sec) ........................ 11.36

    Orbital eccentricity ................................. 0.0000
    Orbital inclination .................................... 1.09°

    Escape velocity (km/sec) .............................. 0.436

    Visual geometric albedo ................................. 0.9
    Magnitude (Vo) ......................................... 10.2
    Mean surface temperature ............................. -187°C

## Views of Tethys

Tethys (GIF, 241K)
This view of Tethys was taken by Voyager 2 on August 26, 1981. It is the highest resolution image acquired by the Voyager spacecraft. An enormous trench named Ithaca Chasma extends from the left side of this image to the upper center. (Credit: Calvin J. Hamilton)

Tethys Color Composite (GIF, 101K)
This view of Tethys is a color composite of three images taken by Voyager 2 on August 25, 1981. (Credit: Calvin J. Hamilton)

Saturn Enceladus Telesto & Calypso

##### Author: Calvin J. Hamilton.