galileo moon callisto


The Discovery of Callisto

The Discovery of Callisto

Callisto is the fourth of jupiter's moons to be discovered by Galileo Galiei on Jan. 7, 1610. The discovery, along with three other Jovian moons, was the first time a moon was discovered orbiting a planet other than Earth. Galileo’s discovery eventually led to the understanding that planets orbit the sun, instead of our solar system revolving around Earth.

Callisto’s Name

Galileo called this moon Jupiter IV. When the numerical naming system was abandoned in the mid-1800s, the moon was named after the daughter of the King of Arcadia, Lycaon, who was a companion of Artemis, the chaste hunting goddess. Like all of the Greek mythological figures used to name the Jupiter moons, Callisto was seduced by Zeus and became pregnant. To protect Callisto and their son from his jealous wife, Hera, Zeus transformed them into bears and positioned them in the sky where he could watch over them.

Exploration of Callisto

Several spacecraft have flown by Jupiter and its moons. Pioneer 10 arrived first, in 1973, followed by Pioneer 11 in 1974. Voyager 1 and Voyager 2 returned striking photos during their flybys. The Galileo spacecraft passed as low as 162 miles (261 km) over the surfaces of the Galilean moons and produced detailed images.

facts about callisto

Jupiter’s moon Callisto is the most heavily cratered object in the solar system. It also has the oldest landscape. It is thought to be a long dead world, with hardly any geologic activity on its surface. Age: Callisto is about 4.5 billion years old, about the same age as Jupiter.

Callisto: Jupiter's Dead Moon | Video

Callisto is the outermost of Jupiter's large moons. Only slightly smaller than the planet Mercury, (roughly 3000 miles in diameter) Callisto is the most heavily cratered moon in our solar system.

With the oldest surface in our solar system, Callisto's exterior still displays the elements it was born with over four billion years ago.

Though the geology of Callisto remains a mystery, there is evidence that below its ancient, icy surface may lay a narrow salty ocean.

Callisto has been called "boring" since its features are not as remarkable as the other three main moons. Callisto is also the darkest of the moons, but is in fact brighter than our Moon (by reflection - called Albedo).Callisto is 4,800 km in diameter and is 1,883,800 km away from Jupiter.

The surface of Callisto is best described as "dirt ice" and is covered with an unknown dark mineral deposit.

The feature above is called Valhalla Basin, and is one of the larger impact craters discovered. The multi-ring appearance is a result of the shock of impact.

Like Ganymede, Callisto does have a tenuous atmosphere composed of mostly carbon dioxide. It is believed the gas emanates from the poles - where its cold enough for carbon dioxide ice to form. This is a surprise since the Voyager data suggested Callisto is a "dead world" meaning there is no magnetic field, no geological activity and no atmosphere.

While geologic activity is not evident, what is present is a small magnetic field. Because its believed Callisto has a very small non-metallic core, a liquid ocean under the crust might be responsible.

The image above demonstrates a large number of impacts - evidence that little or no geologic activity is present.