Callisto

Definition

Callisto is one of the four major moons of Jupiter, discovered by Galileo Galilei in 1610. It is the second-largest and third-most-massive of the Galilean moons, and the fourth-largest moon in the Solar System.

5 Must Know Facts For Your Next Test

1. Callisto has a heavily cratered surface, indicating an ancient and geologically inactive world.
2. It has the lowest density of the Galilean moons, suggesting a composition dominated by water ice.
3. Callisto's orbit around Jupiter is in a retrograde direction, meaning it orbits in the opposite direction to Jupiter's rotation.
4. The surface of Callisto is characterized by a lack of tectonic activity and a heavily cratered appearance, similar to the surface of Earth's Moon.
5. Callisto is the most distant of the Galilean moons from Jupiter, with an average orbital radius of about 1.88 million kilometers.

Review Questions

• Describe the key physical characteristics of Callisto, the second-largest of Jupiter's Galilean moons.
  • Callisto is a heavily cratered, geologically inactive moon with a composition dominated by water ice. It has the lowest density of the Galilean moons, suggesting a high ice content. Callisto's surface is characterized by a lack of tectonic activity and a heavily cratered appearance, similar to Earth's Moon. It is the most distant of the Galilean moons from Jupiter, orbiting at an average distance of about 1.88 million kilometers.
• Explain the significance of Callisto's retrograde orbit around Jupiter.
  • Callisto's orbit around Jupiter is in a retrograde direction, meaning it revolves around the planet in the opposite direction to Jupiter's own rotation. This retrograde orbit is an important characteristic that provides insights into the formation and evolution of the Jovian system. Retrograde orbits are relatively rare in the Solar System and can offer clues about the early conditions and processes that shaped the Jupiter system, including the capture or formation of its moons.
• Analyze how Callisto's heavily cratered surface and geologically inactive nature compare to the other Galilean moons, and what this suggests about its history and evolution.
  • Compared to the other Galilean moons, Callisto's heavily cratered surface and lack of tectonic activity suggest that it is the most geologically inactive of the group. This indicates that Callisto has experienced a relatively quiescent history, with little internal heating or resurfacing events, unlike the more geologically dynamic moons such as Io and Europa. The ancient, heavily cratered appearance of Callisto's surface implies that it has not undergone significant geological change for billions of years, providing insights into the early formation and evolution of the Jovian system.

Related terms

Galilean Moons:

The four largest moons of Jupiter, discovered by Galileo Galilei, which include Io, Europa, Ganymede, and Callisto.

Retrograde Orbit:

An orbit in which a moon or planet revolves around its parent body in the opposite direction to the parent's rotation.

Cryosphere: The frozen component of a planetary body, including ice caps, glaciers, and permafrost.