# Mimas

Saturn I

Mimas [MY-mass] is one of the innermost moons of Saturn. Mimas was a Titan who was slain by Hercules. William Herschel discovered the moon in 1789. The surface is icy and heavily cratered. Mimas has a low density, meaning it probably consists mostly of ice. Because Mimas has such a low temperature of about -200° C (-328°F), the impact features may date back to the time of the moon's creation.

One of the craters, named Herschel, is surprisingly large in comparison to the size of the moon. The crater is 130 kilometers (80 miles) wide, one-third the diameter of Mimas. Herschel is 10 kilometers (6 miles) deep, with a central mountain almost as high as Mount Everest on Earth. This central peak rises 6 kilometers (4 miles) above the crater floor. This impact probably came close to disintegrating the moon. Traces of fracture marks can be seen on the opposite side of Mimas.

Although Mimas is heavily cratered, the cratering is not uniform. Most of the surface is covered with craters greater than 40 kilometers (25 miles) in diameter but in the south polar region, craters greater than 20 kilometers (12 miles) are generally lacking. This suggests that some process removed the larger craters from these areas.

## Mimas Statistics

    Discovered by .............................. William Herschel
    Date of discovery ...................................... 1789

    Mass (kg) .......................................... 3.80e+19
    Mass (Earth = 1) ................................. 6.3588e-06
    Equatorial radius (km) .................................. 196
    Equatorial radius (Earth = 1) .................... 3.0731e-02
    Mean density (gm/cm^3) ................................. 1.17

    Mean distance from Saturn (km) ...................... 185,520
    Rotational period (days) ........................... 0.942422
    Orbital period (days) .............................. 0.942422
    Mean orbital velocity (km/sec) ........................ 14.32

    Orbital eccentricity ................................. 0.0202
    Orbital inclination .................................... 1.53°

    Escape velocity (km/sec) .............................. 0.161

    Visual geometric albedo ................................. 0.5
    Mean surface temperature ............................. -200°C
    Magnitude (Vo) ......................................... 12.9

## Views of Mimas

Mimas & Herschel Crater (GIF, 13K)
This image of Mimas was acquired by the Voyager 1 spacecraft on November 11, 1980. The large crater on the right limb is named Herschel. It is 130 kilometers (80 miles) wide and one-third the diameter of Mimas. Herschel is 10 kilometers (6 miles) deep, with a central mountain almost as high as Mount Everest on Earth. This impact probably came close to disintegrating the moon. (Credit: Calvin J. Hamilton)

Mimas (GIF, 87K)
This image of Mimas was acquired by the Voyager 1 spacecraft on November 13, 1980. Traces of fracture marks, probably due to the Herschel Impact, can be seen on this side of Mimas. (Credit: Calvin J. Hamilton)

Saturn Janus Enceladus

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