Excerpt
Introduction: A Mysterious Moon
Europa is out there, circling Jupiter, locked in a never-ending dance with the biggest planet in the solar system. If you could stand on its surface—though you’d need a space suit because it’s freezing—you would see Jupiter taking up a huge chunk of the sky. It would be much bigger than the way the Moon looks from Earth. And unlike our familiar, gray, crater-filled Moon, Europa’s surface is bright and smooth, covered in ice that stretches as far as the eye can see. But the real excitement isn’t just what’s on top. It’s what’s hiding underneath.
Underneath that thick shell of ice is an ocean. A deep, dark ocean that might be teeming with life. And that’s what makes Europa one of the most fascinating places in our entire solar system.
Jupiter has a lot of moons. Over 90 of them, actually. Some are big, some are small, and a few are just chunks of rock floating along in Jupiter’s gravitational pull. But Europa is special. It’s one of the four Galilean moons—the biggest and brightest of Jupiter’s moons that were first spotted by astronomer Galileo Galilei back in 1610. Even with his simple telescope, he could see that Europa was something different.
Fast forward a few hundred years, and scientists have learned a lot more about it. Spacecraft have flown by, snapping pictures and collecting data. Every time we’ve gotten a closer look, Europa has only become more interesting. The surface is covered in cracks and lines, almost like someone took a giant ice cube and scratched it up with a knife. But these aren’t just random marks—they’re clues. Clues that Europa’s ice is moving, shifting, cracking open, and maybe even letting water from below rise up to the surface. That’s huge because where there’s liquid water, there’s a chance for life.
Earth’s oceans are filled with creatures in places we never expected. In the deepest parts of the ocean, where sunlight never reaches, life still thrives. Giant tube worms, glowing jellyfish, strange fish with see-through heads—all of them survive without sunlight. Instead of using the Sun’s energy like plants on land do, these creatures rely on heat and chemicals coming from deep-sea vents. These vents are like underwater volcanoes, spewing out hot, mineral-rich water. That’s important because Europa might have something similar.
Under its ice, Europa’s ocean could have hydrothermal vents, places where heat from inside the moon escapes into the water. If that’s true, then Europa could be home to alien life. Not the kind of aliens in movies with flying saucers and laser beams, but microscopic creatures, bacteria, or even something swimming around in the dark, completely unaware that a giant planet looms above them.
Of course, no one knows for sure. That’s the mystery scientists are trying to solve. They’ve sent probes to take pictures, studied Europa from telescopes on Earth, and even designed missions that will one day dive beneath the ice and see what’s hiding down there. If we ever find life on Europa, it will change everything we know about the universe.
Right now, Earth is the only planet we know for sure has life. But if there’s life on Europa, it means that life might not be as rare as we thought. It might mean that oceans all across the universe, on moons and planets we haven’t even discovered yet, could be full of strange, alien creatures. And that’s the kind of discovery that could reshape how we think about space forever.
What makes Europa so special?
Out of all the moons in the solar system, why does Europa stand out? Jupiter has dozens of moons, and some of them are massive. Ganymede, for example, is even bigger than the planet Mercury. Io is covered in active volcanoes, constantly spewing lava into space. Callisto is covered in craters and might have an underground ocean, too. But Europa is different. There’s something about it that keeps scientists coming back, asking questions, and sending missions to learn more.
For starters, there’s the ice. Europa’s surface is like a frozen puzzle, covered in long, dark lines that crisscross like the cracks on a frozen lake. That might not sound exciting at first—lots of places in the solar system have ice. Pluto has ice, Saturn’s moon Enceladus has ice, even comets are made of frozen material. But Europa’s ice is special because of what’s underneath it.
A long time ago, scientists thought Europa was just another cold, dead moon, the kind of place where nothing ever changed. Then spacecraft like Voyager and Galileo sent back images showing something unusual. The cracks on Europa’s surface didn’t look like old, weathered scars. They looked fresh, as if something had broken through the ice recently. And when scientists studied how Jupiter’s gravity pulls on Europa, they realized something incredible—the ice wasn’t sitting on solid rock. It was floating on liquid water.
That discovery changed everything. It meant Europa wasn’t just an icy moon. It was an icy moon with an ocean, possibly the biggest ocean in the entire solar system. Scientists believe that beneath its thick ice shell, Europa holds more water than all of Earth’s oceans combined.
Think about that for a second. Earth is a water planet. Oceans cover most of its surface. Whales, sharks, dolphins, and millions of other creatures live in the depths of the sea. But Europa—this tiny moon orbiting Jupiter—might have even more water than Earth. And where there’s water, there’s the potential for life.
Of course, not just any water will do. A frozen block of ice floating through space isn’t going to have fish swimming around inside it. Life needs liquid water, a place where molecules can move around, mix together, and form something new. That’s why Europa’s hidden ocean is such a big deal. Scientists believe it has been liquid for billions of years, meaning there has been plenty of time for life to develop, if the right conditions exist.
But there’s another mystery—how does Europa’s ocean stay liquid? The surface is extremely cold, much colder than the coldest places on Earth. The ice is frozen solid, and there’s no sunlight to warm it up. The secret lies in Europa’s relationship with Jupiter.
Europa isn’t just orbiting Jupiter like Earth orbits the Sun. It’s caught in a constant tug-of-war. Jupiter’s gravity pulls on Europa, stretching and squishing it like a stress ball. Other nearby moons, like Io and Ganymede, also pull on Europa, making its orbit slightly uneven. All this tugging creates friction deep inside the moon, and friction creates heat. That heat keeps the ocean from freezing, just like the inside of Earth stays warm even though space is freezing cold.
This process, called tidal heating, might also create something even more exciting—underwater volcanoes. On Earth, volcanic vents at the bottom of the ocean create environments where life thrives, even without sunlight. Bacteria feed off the minerals and heat from these vents, and larger creatures like giant tube worms, crabs, and strange fish survive because of them. If Europa has similar hydrothermal vents at the bottom of its ocean, they could be a source of energy for alien life.
Of course, no one has actually seen what’s under Europa’s ice. No spacecraft has ever landed there, no probe has ever drilled down to the ocean. Everything scientists know about Europa comes from spacecraft flying by, collecting data from a distance. But that’s about to change. NASA is planning to send a mission called Europa Clipper, which will orbit Jupiter and take the closest look at Europa yet. It will study the surface, measure the thickness of the ice, and look for signs of water plumes—jets of water shooting up from cracks in the ice.
Those plumes might be the key to finding life. If Europa’s ocean sometimes leaks water into space, a spacecraft could fly through it and test it for signs of living things. Scientists already know that another icy moon, Enceladus, has water plumes that contain organic molecules—the building blocks of life. If Europa’s plumes contain something similar, it would be one of the strongest clues yet that something is swimming around down there.
Europa is out there, circling Jupiter, locked in a never-ending dance with the biggest planet in the solar system. If you could stand on its surface—though you’d need a space suit because it’s freezing—you would see Jupiter taking up a huge chunk of the sky. It would be much bigger than the way the Moon looks from Earth. And unlike our familiar, gray, crater-filled Moon, Europa’s surface is bright and smooth, covered in ice that stretches as far as the eye can see. But the real excitement isn’t just what’s on top. It’s what’s hiding underneath.
Underneath that thick shell of ice is an ocean. A deep, dark ocean that might be teeming with life. And that’s what makes Europa one of the most fascinating places in our entire solar system.
Jupiter has a lot of moons. Over 90 of them, actually. Some are big, some are small, and a few are just chunks of rock floating along in Jupiter’s gravitational pull. But Europa is special. It’s one of the four Galilean moons—the biggest and brightest of Jupiter’s moons that were first spotted by astronomer Galileo Galilei back in 1610. Even with his simple telescope, he could see that Europa was something different.
Fast forward a few hundred years, and scientists have learned a lot more about it. Spacecraft have flown by, snapping pictures and collecting data. Every time we’ve gotten a closer look, Europa has only become more interesting. The surface is covered in cracks and lines, almost like someone took a giant ice cube and scratched it up with a knife. But these aren’t just random marks—they’re clues. Clues that Europa’s ice is moving, shifting, cracking open, and maybe even letting water from below rise up to the surface. That’s huge because where there’s liquid water, there’s a chance for life.
Earth’s oceans are filled with creatures in places we never expected. In the deepest parts of the ocean, where sunlight never reaches, life still thrives. Giant tube worms, glowing jellyfish, strange fish with see-through heads—all of them survive without sunlight. Instead of using the Sun’s energy like plants on land do, these creatures rely on heat and chemicals coming from deep-sea vents. These vents are like underwater volcanoes, spewing out hot, mineral-rich water. That’s important because Europa might have something similar.
Under its ice, Europa’s ocean could have hydrothermal vents, places where heat from inside the moon escapes into the water. If that’s true, then Europa could be home to alien life. Not the kind of aliens in movies with flying saucers and laser beams, but microscopic creatures, bacteria, or even something swimming around in the dark, completely unaware that a giant planet looms above them.
Of course, no one knows for sure. That’s the mystery scientists are trying to solve. They’ve sent probes to take pictures, studied Europa from telescopes on Earth, and even designed missions that will one day dive beneath the ice and see what’s hiding down there. If we ever find life on Europa, it will change everything we know about the universe.
Right now, Earth is the only planet we know for sure has life. But if there’s life on Europa, it means that life might not be as rare as we thought. It might mean that oceans all across the universe, on moons and planets we haven’t even discovered yet, could be full of strange, alien creatures. And that’s the kind of discovery that could reshape how we think about space forever.
What makes Europa so special?
Out of all the moons in the solar system, why does Europa stand out? Jupiter has dozens of moons, and some of them are massive. Ganymede, for example, is even bigger than the planet Mercury. Io is covered in active volcanoes, constantly spewing lava into space. Callisto is covered in craters and might have an underground ocean, too. But Europa is different. There’s something about it that keeps scientists coming back, asking questions, and sending missions to learn more.
For starters, there’s the ice. Europa’s surface is like a frozen puzzle, covered in long, dark lines that crisscross like the cracks on a frozen lake. That might not sound exciting at first—lots of places in the solar system have ice. Pluto has ice, Saturn’s moon Enceladus has ice, even comets are made of frozen material. But Europa’s ice is special because of what’s underneath it.
A long time ago, scientists thought Europa was just another cold, dead moon, the kind of place where nothing ever changed. Then spacecraft like Voyager and Galileo sent back images showing something unusual. The cracks on Europa’s surface didn’t look like old, weathered scars. They looked fresh, as if something had broken through the ice recently. And when scientists studied how Jupiter’s gravity pulls on Europa, they realized something incredible—the ice wasn’t sitting on solid rock. It was floating on liquid water.
That discovery changed everything. It meant Europa wasn’t just an icy moon. It was an icy moon with an ocean, possibly the biggest ocean in the entire solar system. Scientists believe that beneath its thick ice shell, Europa holds more water than all of Earth’s oceans combined.
Think about that for a second. Earth is a water planet. Oceans cover most of its surface. Whales, sharks, dolphins, and millions of other creatures live in the depths of the sea. But Europa—this tiny moon orbiting Jupiter—might have even more water than Earth. And where there’s water, there’s the potential for life.
Of course, not just any water will do. A frozen block of ice floating through space isn’t going to have fish swimming around inside it. Life needs liquid water, a place where molecules can move around, mix together, and form something new. That’s why Europa’s hidden ocean is such a big deal. Scientists believe it has been liquid for billions of years, meaning there has been plenty of time for life to develop, if the right conditions exist.
But there’s another mystery—how does Europa’s ocean stay liquid? The surface is extremely cold, much colder than the coldest places on Earth. The ice is frozen solid, and there’s no sunlight to warm it up. The secret lies in Europa’s relationship with Jupiter.
Europa isn’t just orbiting Jupiter like Earth orbits the Sun. It’s caught in a constant tug-of-war. Jupiter’s gravity pulls on Europa, stretching and squishing it like a stress ball. Other nearby moons, like Io and Ganymede, also pull on Europa, making its orbit slightly uneven. All this tugging creates friction deep inside the moon, and friction creates heat. That heat keeps the ocean from freezing, just like the inside of Earth stays warm even though space is freezing cold.
This process, called tidal heating, might also create something even more exciting—underwater volcanoes. On Earth, volcanic vents at the bottom of the ocean create environments where life thrives, even without sunlight. Bacteria feed off the minerals and heat from these vents, and larger creatures like giant tube worms, crabs, and strange fish survive because of them. If Europa has similar hydrothermal vents at the bottom of its ocean, they could be a source of energy for alien life.
Of course, no one has actually seen what’s under Europa’s ice. No spacecraft has ever landed there, no probe has ever drilled down to the ocean. Everything scientists know about Europa comes from spacecraft flying by, collecting data from a distance. But that’s about to change. NASA is planning to send a mission called Europa Clipper, which will orbit Jupiter and take the closest look at Europa yet. It will study the surface, measure the thickness of the ice, and look for signs of water plumes—jets of water shooting up from cracks in the ice.
Those plumes might be the key to finding life. If Europa’s ocean sometimes leaks water into space, a spacecraft could fly through it and test it for signs of living things. Scientists already know that another icy moon, Enceladus, has water plumes that contain organic molecules—the building blocks of life. If Europa’s plumes contain something similar, it would be one of the strongest clues yet that something is swimming around down there.