How Big Is Callisto Compared To Earth? An In-Depth Comparison

Discover how Callisto stacks up against Earth in size, composition, and other key features, providing a comprehensive comparison on COMPARE.EDU.VN and helping you understand their place in the solar system. This guide breaks down the celestial comparison and other aspects.

1. What Is the Size Comparison Between Callisto and Earth?

Callisto, one of Jupiter’s largest moons, is significantly smaller than Earth. Callisto has a diameter of approximately 4,821 kilometers (2,996 miles), while Earth has a diameter of about 12,742 kilometers (7,918 miles). This means Earth is approximately 2.6 times larger than Callisto in diameter. This size difference profoundly influences their geological activities, atmospheres, and potential habitability, making Earth a dynamic planet and Callisto a relatively inactive moon.

Diameter: Callisto: 4,821 km (2,996 mi), Earth: 12,742 km (7,918 mi)
Volume: Earth is roughly 15 times the volume of Callisto.
Surface Area: Earth’s surface area is about 6.3 times that of Callisto.

2. What Are the Key Physical Characteristics of Callisto?

Callisto, the second-largest moon of Jupiter and the third-largest in our solar system, presents a unique and heavily cratered surface. Unlike many other celestial bodies, Callisto’s surface is ancient and has remained relatively unchanged over billions of years, offering scientists a glimpse into the early solar system.

Surface Composition: Callisto’s surface is composed of approximately 40% ice, 35% rock, and 25% other ices, such as carbon dioxide, sulfur dioxide, and organic compounds.
Atmosphere: Callisto possesses a very thin atmosphere composed primarily of carbon dioxide and trace amounts of molecular oxygen.
Geological Activity: One of the most distinguishing features of Callisto is its lack of significant geological activity. The surface is old and heavily cratered, indicating minimal internal processes compared to other moons like Io or Europa.
Notable Features:
- Valhalla: The most prominent feature on Callisto is the Valhalla impact crater. This multi-ring structure spans approximately 3,800 kilometers (2,361 miles) in diameter, making it one of the largest impact craters in the solar system.
- Gipul Catena: A long chain of impact craters stretching across Callisto’s surface, likely formed by an object that was tidally disrupted before impact.
Internal Structure: Scientists believe Callisto has a differentiated interior, consisting of a core, mantle, and crust. However, unlike other Jovian moons, Callisto’s interior is not fully differentiated. It likely consists of a mixture of rock and ice.
Magnetic Field: Callisto has a weak magnetic field that varies depending on Jupiter’s magnetic field. This suggests the possibility of a subsurface ocean of salty liquid water.

3. How Does Callisto’s Density Compare to Earth’s?

Callisto is less dense than Earth due to its composition, which includes a significant amount of ice and rock. Callisto has a density of about 1.83 g/cm³, while Earth has a density of approximately 5.51 g/cm³.

Callisto’s Density: 1.83 g/cm³
Earth’s Density: 5.51 g/cm³
Implications: The lower density of Callisto indicates that it is composed of lighter materials such as water ice, whereas Earth is primarily composed of heavier rocky and metallic materials.

4. What Are the Surface Features of Callisto Compared to Earth?

Callisto’s surface is characterized by its ancient, heavily cratered terrain, in stark contrast to Earth’s dynamic and ever-changing landscape. Callisto’s surface features are primarily impact craters and multi-ring structures, indicating minimal geological activity over billions of years.

Heavily cratered surface of Callisto

Callisto:
- Impact Craters: Dominated by numerous impact craters of varying sizes.
- Valhalla Crater: A massive multi-ring structure, one of the largest impact features in the solar system.
- Gipul Catena: A chain of craters believed to be formed by a string of impacts.
- Lack of Tectonic Activity: No evidence of plate tectonics, volcanoes, or mountains.
Earth:
- Diverse Terrain: Features mountains, valleys, plains, and oceanic trenches.
- Plate Tectonics: Active plate tectonics result in the formation of mountain ranges, volcanic activity, and earthquakes.
- Erosion: Significant erosion due to wind, water, and ice.
- Oceans: About 71% of Earth’s surface is covered by water.

5. How Does the Gravity of Callisto Compare to Earth?

The gravity on Callisto is much weaker than on Earth due to its smaller mass and lower density. Callisto has a surface gravity of about 1.235 m/s², which is approximately 0.126 g (where g is the acceleration due to gravity on Earth, approximately 9.8 m/s²).

Callisto’s Surface Gravity: 1.235 m/s² (0.126 g)
Earth’s Surface Gravity: 9.8 m/s² (1 g)
Implications: On Callisto, you would weigh only about 12.6% of what you weigh on Earth. This lower gravity would significantly affect the environment and potential for sustaining life as we know it.

6. What Is the Atmospheric Composition of Callisto Compared to Earth?

Callisto’s atmosphere is extremely thin and primarily composed of carbon dioxide and trace amounts of molecular oxygen, while Earth has a dense atmosphere composed mainly of nitrogen and oxygen.

Callisto:
- Main Components: Carbon dioxide (CO₂) and trace amounts of molecular oxygen (O₂).
- Density: Extremely thin, with a surface pressure that is negligible compared to Earth’s.
- Origin: The oxygen may be produced by the decomposition of water ice on the surface due to radiation.
Earth:
- Main Components: Nitrogen (N₂) approximately 78%, Oxygen (O₂) approximately 21%, Argon (Ar) approximately 0.9%, and trace amounts of other gases.
- Density: Relatively dense, providing a protective layer against solar radiation and maintaining a stable temperature.
- Importance: Essential for supporting life, regulating temperature, and protecting the surface from harmful radiation.

7. How Do the Orbital Characteristics of Callisto Differ From Earth?

Callisto orbits Jupiter, while Earth orbits the Sun. Callisto takes approximately 16.7 Earth days to orbit Jupiter, whereas Earth takes about 365.25 days to orbit the Sun. The distance from Callisto to Jupiter is about 1.88 million kilometers (1.17 million miles), while Earth is about 149.6 million kilometers (93 million miles) from the Sun.

Callisto:
- Orbit: Around Jupiter
- Orbital Period: Approximately 16.7 Earth days
- Distance from Primary: About 1.88 million kilometers (1.17 million miles) from Jupiter
- Tidal Locking: Callisto is tidally locked with Jupiter, meaning one side always faces the planet.
Earth:
- Orbit: Around the Sun
- Orbital Period: Approximately 365.25 days
- Distance from Primary: About 149.6 million kilometers (93 million miles) from the Sun
- Seasons: Earth’s axial tilt of about 23.5 degrees results in distinct seasons.

8. What Is the Temperature Range on Callisto Compared to Earth?

Callisto experiences extremely cold temperatures due to its distance from the Sun and thin atmosphere, whereas Earth has a wider range of temperatures due to its atmosphere and proximity to the Sun.

Callisto:
- Temperature Range: Approximately -193°C to -108°C (-315°F to -162°F)
- Factors: Distance from the Sun, thin atmosphere, and low albedo.
Earth:
- Temperature Range: Approximately -89°C to 57°C (-128°F to 135°F)
- Factors: Atmosphere, proximity to the Sun, and diverse geographical features.

9. How Does the Magnetic Field of Callisto Compare to Earth?

Callisto has a very weak induced magnetic field, while Earth has a strong intrinsic magnetic field generated by its molten iron core.

Callisto:
- Magnetic Field: Very weak induced magnetic field.
- Origin: Believed to be caused by the interaction of Jupiter’s magnetic field with a subsurface ocean of salty liquid water.
- Strength: Approximately 100 times weaker than Earth’s magnetic field.
Earth:
- Magnetic Field: Strong intrinsic magnetic field.
- Origin: Generated by the movement of molten iron in Earth’s outer core (the geodynamo effect).
- Function: Protects the planet from harmful solar wind and cosmic radiation.

10. What Is the Potential for Life on Callisto Compared to Earth?

The potential for life on Callisto is considered low compared to Earth, primarily due to its lack of a substantial atmosphere, extreme temperatures, and limited energy sources.

Callisto:
- Factors Against Life:
  - Thin Atmosphere: Offers minimal protection from radiation and micrometeoroids.
  - Extreme Temperatures: Surface temperatures are extremely cold.
  - Limited Energy Sources: Lack of volcanic activity or other internal heat sources.
  - Simplicity: There may be a liquid ocean within the moon but it lacks interaction with mineral layers.
- Potential Habitable Zones:
  - Subsurface Ocean: Some scientists speculate that a subsurface ocean could potentially harbor microbial life, similar to Europa.
  - Radiation Shielding: The icy surface might provide some protection from radiation.
Earth:
- Factors Supporting Life:
  - Abundant Liquid Water: Covers approximately 71% of the surface.
  - Protective Atmosphere: Regulates temperature and shields the surface from harmful radiation.
  - Stable Climate: Provides a stable environment for life to evolve.
  - Energy Sources: Sunlight, geothermal energy, and chemical energy support a wide range of ecosystems.

11. How Does Callisto’s Internal Structure Compare to Earth’s?

Callisto is believed to have a less differentiated internal structure compared to Earth, with a possible subsurface ocean. Earth has a distinct layered structure with a solid inner core, a liquid outer core, a mantle, and a crust.

Callisto:
- Core: Likely composed of compressed rock and ice.
- Mantle: Primarily a mix of ice and rock.
- Crust: Icy and heavily cratered.
- Subsurface Ocean: Possible layer of salty liquid water.
Earth:
- Inner Core: Solid iron and nickel.
- Outer Core: Liquid iron and nickel, responsible for Earth’s magnetic field.
- Mantle: Composed of silicate rocks.
- Crust: Thin outer layer composed of either oceanic or continental crust.

12. What Missions Have Explored Callisto and Earth?

Several missions have explored Callisto, providing valuable data about its surface and composition, while numerous missions have extensively studied Earth from space and the ground.

Callisto:
- Voyager 1 and 2: Provided initial images and data about Callisto’s surface.
- Galileo: Orbited Jupiter from 1995 to 2003 and provided detailed images and data about Callisto’s geology, atmosphere, and magnetic field.
- Future Missions: The Europa Clipper mission, launching in 2024, may provide additional data about Callisto during its exploration of Jupiter’s moons.
Earth:
- Numerous Satellites: Missions like Landsat, Terra, Aqua, and many others monitor Earth’s climate, weather, and environment.
- Space Shuttle Missions: Conducted numerous experiments and observations of Earth.
- International Space Station (ISS): Provides a platform for long-term observations and research.

13. How Does the Surface Age of Callisto Compare to Earth?

Callisto has a very old surface, estimated to be around 4 billion years old, making it one of the oldest and most heavily cratered surfaces in the solar system. Earth’s surface is relatively young, with continuous geological activity renewing and reshaping it over time.

Callisto:
- Surface Age: Approximately 4 billion years old.
- Characteristics: Heavily cratered, indicating minimal geological activity.
Earth:
- Surface Age: Varies depending on the region, but much younger on average than Callisto.
- Characteristics: Continuously reshaped by plate tectonics, erosion, and volcanic activity.

14. What Geological Processes Are Evident on Callisto and Earth?

Callisto exhibits minimal geological activity, with its surface primarily shaped by impact cratering. Earth displays a wide range of geological processes, including plate tectonics, volcanism, erosion, and sedimentation.

Callisto:
- Impact Cratering: The primary geological process.
- Lack of Tectonic Activity: No evidence of plate tectonics or volcanic activity.
- Surface Degradation: Slow degradation of surface features due to micrometeoroid impacts and sublimation.
Earth:
- Plate Tectonics: Drives the formation of mountain ranges, ocean trenches, and volcanic activity.
- Volcanism: Eruptions release molten rock and gases onto the surface.
- Erosion: Wind, water, and ice erode and reshape the landscape.
- Sedimentation: Deposition of sediments forms sedimentary rocks.

15. How Do the Sizes of Impact Craters on Callisto and Earth Compare?

Callisto has some of the largest impact craters in the solar system, such as the Valhalla crater, due to its ancient surface and lack of geological activity. Earth’s impact craters are generally smaller and less numerous due to erosion and tectonic activity.

Callisto:
- Valhalla Crater: Approximately 3,800 kilometers (2,361 miles) in diameter.
- Other Craters: Numerous large craters covering much of the surface.
Earth:
- Larger Craters: Vredefort crater in South Africa (approximately 300 kilometers in diameter) and Sudbury Basin in Canada (approximately 250 kilometers in diameter).
- Smaller Craters: Erosion and tectonic activity have erased many impact craters over time.

16. What Is the Tidal Locking Status of Callisto and How Does It Affect Its Environment?

Callisto is tidally locked with Jupiter, meaning that it always presents the same face to the planet. This tidal locking affects the distribution of heat and potentially influences the moon’s internal structure and subsurface ocean.

Callisto:
- Tidal Locking: One side always faces Jupiter.
- Effects:
  - Heat Distribution: Uneven distribution of tidal forces and heat across the surface.
  - Internal Structure: May influence the shape and dynamics of the subsurface ocean.
  - Surface Features: Could affect the distribution and orientation of surface features over long periods.
Earth:
- Tidal Locking: Earth is not tidally locked with the Sun, but the Moon is tidally locked with Earth.
- Effects:
  - Tides: The Moon’s tidal locking causes tides on Earth, influencing coastal environments.
  - Stabilization: The Moon stabilizes Earth’s axial tilt, contributing to climate stability.

17. How Does Callisto’s Albedo Compare to Earth’s?

Callisto has a relatively low albedo (reflectivity) compared to Earth, meaning it reflects less sunlight back into space.

Callisto:
- Albedo: Approximately 0.22.
- Implications: Absorbs more sunlight, contributing to its cold surface temperatures.
Earth:
- Albedo: Average of about 0.3.
- Implications: Reflects more sunlight, helping to regulate Earth’s temperature.

18. What Are the Implications of Callisto’s Subsurface Ocean?

The potential existence of a subsurface ocean on Callisto raises intriguing questions about its habitability and internal structure. The ocean may be sustained by heat from radioactive decay and could potentially harbor microbial life.

Callisto:
- Subsurface Ocean: Possible layer of salty liquid water.
- Implications:
  - Habitability: Could potentially support microbial life.
  - Magnetic Field: May explain the induced magnetic field.
  - Internal Dynamics: Could influence the moon’s internal structure and dynamics.
Earth:
- Oceans: Extensive surface oceans covering approximately 71% of the planet.
- Implications:
  - Life Support: Essential for supporting a wide range of aquatic life.
  - Climate Regulation: Influences weather patterns and temperature distribution.
  - Geological Processes: Contributes to erosion and sedimentation.

19. How Does the Radiation Environment Around Callisto Compare to Earth?

Callisto is located within Jupiter’s strong magnetosphere, exposing it to high levels of radiation, whereas Earth is protected by its own magnetic field.

Callisto:
- Radiation Environment: High levels of radiation due to Jupiter’s magnetosphere.
- Implications:
  - Surface Processes: Can alter the chemical composition of the surface.
  - Habitability Challenges: Poses significant challenges for potential life.
Earth:
- Radiation Environment: Protected by Earth’s magnetic field and atmosphere.
- Implications:
  - Life Support: Allows for the existence of a diverse range of life forms.
  - Climate Stability: Contributes to a stable and habitable climate.

20. What Are the Future Exploration Plans for Callisto?

While there are no specific missions solely dedicated to Callisto currently planned, future missions to the Jovian system, such as the Europa Clipper, may provide additional data and insights about Callisto during their exploration.

Callisto:
- Europa Clipper: This mission will study Europa in detail but may also gather data about Callisto during its orbit around Jupiter.
- Future Missions: Future exploration concepts may include dedicated missions to study Callisto’s subsurface ocean and geological history.
Earth:
- Ongoing Missions: Numerous satellites and ground-based observatories continuously monitor Earth’s climate, environment, and geological processes.
- Future Missions: Planned missions include advanced Earth-observing satellites and research initiatives to address climate change and environmental challenges.

Callisto and Earth are vastly different celestial bodies, each with unique characteristics and histories. Understanding these differences enriches our knowledge of the solar system and the conditions that support life. Whether you’re comparing celestial bodies or evaluating everyday products, visit COMPARE.EDU.VN for detailed, objective comparisons that help you make informed decisions.

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