Facts for Kids

Callisto is one of Jupiter's moons, and it’s the second-largest moon of this giant planet, next to Ganymede! 🌌

Callisto is about 4,820 kilometers (or 2,995 miles) across, which is almost as wide as the planet Mercury! It was discovered in 1610 by the famous scientist Galileo Galilei, along with three other big moons of Jupiter. Callisto is known for its icy surface with many craters, making it a fascinating place to study! It circles Jupiter about every 17 days and is part of the "Galilean moons" along with Io, Europa, and Ganymede. 🚀

The most famous missions that studied Callisto include NASA's Voyager and Galileo missions. 🚀

Voyager 1 and 2 visited Callisto in 1979, taking important photos. Galileo then orbited Jupiter from 1995 to 2003, capturing incredible details about the moon's surface and atmosphere! In 2024, the European Space Agency’s mission called JUICE (JUpiter ICy moons Explorer) will also explore Callisto along with Ganymede and Europa! 🌟

This mission hopes to gather lots of information about these icy moons and their potential for life!

Scientists are curious if Callisto could host any form of life. 🦠

Some believe that beneath its icy surface, there may be an ocean of salty water! Water is essential for life as we know it. However, the extreme cold temperatures and thin atmosphere make it less likely for us to find life like on Earth. 🤔

Scientists are excited to study this moon more because if life does exist, it could be very different from life on our planet!

Callisto has been explored by several spacecraft! 🛰

️ In 1979, NASA's Voyager 1 and Voyager 2 flew by Jupiter and took some amazing pictures of Callisto. These missions helped us learn more about this moon. Then, the Galileo spacecraft studied Callisto in greater detail in the 1990s. Galileo went into orbit around Jupiter and sent back lots of data! 📊

Today, scientists are still studying images and information sent back by these missions to understand Callisto better.

The surface of Callisto is very interesting! 🪨

It has many large craters, like Valhalla, which is over 4,000 kilometers (2,485 miles) wide and has rings around it. When asteroids or comets crash into Callisto, they leave behind big dents or craters. There are also grooves and valleys that scientists believe may have formed from the icy layers below shifting. Even though Callisto is rocky and icy, it doesn’t have any volcanoes like some other moons! 🌌

Instead, it’s mostly quiet and stable, making it a unique place in our Solar System.

Exciting plans for exploring Callisto are in the works! 🚀

The European Space Agency's JUICE mission, launching in 2024, aims to study Callisto and its fellow moons. 🛰

️ Scientists want to learn more about its surface and see if an ocean lies beneath. Other missions may follow, including searches for other moons or robots that could land on Callisto! In the future, we might even send humans to explore it! 🌍

Who knows what we might find? Exploring Callisto could answer many questions about our Solar System!

Callisto's surface is very old, filled with craters! 🌑

It has one of the oldest and most heavily cratered surfaces in the Solar System. Some craters are more than 4 billion years old! This icy moon also has a thin atmosphere made mostly of carbon dioxide. Callisto is covered with frozen water and ice, and scientists think that some areas might have underground oceans of salty water! 🧊

The temperatures on Callisto can be extremely cold, reaching around -139 degrees Celsius (-218 degrees Fahrenheit) at night. It’s like a giant ice ball floating in space!

Callisto is the second-largest of Jupiter's moons. 🌕

While Ganymede is the biggest, Callisto has the most craters of any moon! Its surface is much older than Io, which has many volcanoes. Europa is different too—it is believed to have an ocean beneath its ice. Callisto is more stable and less geologically active than its siblings, making it unique. ☄

️ The other moons have very different features, so learning about each one helps scientists understand more about our Solar System!

Callisto has a very thin atmosphere, mainly made of carbon dioxide. 🌬

️ This atmosphere is too thin for humans to breathe! It doesn't have much pressure, which means it can't keep heat very well. Callisto is also outside of Jupiter's strong magnetic field, so it’s less affected by radiation than other moons, like Io! However, its thin atmosphere means that it can’t hold heat, so it remains extremely cold all the time. ❄

️ Unlike Earth, where our atmosphere protects us from space rocks, Callisto's atmosphere will not help much if something were to fall onto it!

Callisto is named after a figure from Greek mythology. 🌠

According to the myth, she was a beautiful nymph and a follower of the goddess Artemis. There are many stories about Callisto, which show how ancient people tried to explain the world around them! 🌌

This moon has also been featured in popular films and cartoons, sparking imagination and curiosity in young explorers everywhere. Callisto inspires scientists, writers, and artists alike, making it a well-loved name in both science and storytelling! 💫