# Callisto

Man's mind and spirit grow with the space in which they are allowed to operate. - Krafft A. Ehricke

Jupiter IV

Callisto [kah-LISS-toe] is the second largest moon of Jupiter. It has no atmosphere and is about the same size as Mercury. It is composed of approximately equal proportions of ice-water and rock. Its crust is very old and heavily cratered with remnant rings of enormous impact craters. The largest craters have been erased by the flow of the icy crust over geologic time. Craters and the associated concentric rings are about the only features to be found on Callisto.

The moon is probably composed of a large rocky core surrounded by water and ice, giving it a dark color. Meteorites have punctured holes in the crust, causing water to spread over the surface and forming bright rays and rings around the crater.

## Callisto Statistics

    Discovered by ................ Simon Marius & Galileo Galilei
    Date of discovery ...................................... 1610

    Mass (kg) .......................................... 1.08e+23
    Mass (Earth = 1) ................................. 1.8072e-02
    Equatorial radius (km) ................................ 2,400
    Equatorial radius (Earth = 1) .................... 3.7629e-01
    Mean density (gm/cm^3) ................................. 1.86

    Mean distance from Jupiter (km) ................... 1,883,000
    Rotational period (days) ........................... 16.68902
    Orbital period (days) .............................. 16.68902
    Mean orbital velocity (km/sec) ......................... 8.21

    Orbital eccentricity .................................. 0.007
    Orbital inclination ................................... 0.281°

    Escape Velocity (km/sec) ............................... 2.45

    Visual geometric albedo ................................ 0.20
    Magnitude (Vo) ......................................... 5.65

## Views of Callisto

Callisto (GIF, 240K)
This image shows the heavily cratered surface of Callisto. It was taken by Voyager 2 on July 7, 1979. An enormous impact basin with concentric rings is located near the top and slightly left of center. (Credit: Calvin J. Hamilton)

High-Resolution Image of Callisto (GIF, 2M)
This high-resolution image of Callisto shows its heavily cratered surface. The impact basin, Valhalla, is located towards the bottom-left of the image. (Credit: Calvin J. Hamilton)

Callisto's Valhalla Region (GIF, 775K)
This close up of Callisto shows the heavily cratered surface and the prominent ring structure known as Valhalla. It was acquired by Voyager 1 on March 6, 1979. Valhalla's bright central area is about 300 kilometers across with sets of concentric ridges extending out to 1,500 kilometers from the center. (Credit: Calvin J. Hamilton)

Gipul Catena (GIF, 114K)
This image of an chain of craters on Callisto is 620 kilometers long. The largest crater is 40 kilometers across. This is the longest of 12 or so such chains on Callisto. The chain probably formed from the collision of a comet that was tidally disrupted during close passage of Jupiter, such as the comet Shoemaker-Levy 9. (Credit: Calvin J. Hamilton)

Jupiter Ganymede Leda

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