Europa is one of the 79 known moons orbiting Jupiter. An interesting thing to note is that if Jupiter had continued to grow it would be a gas giant that could have become a sun and the moons would give it its own solar system.

Over the years, scientific research has led astronomers to believe that Europa may be the most promising objects in our solar system for potential life. Europa is just a bit smaller than our moon and when you see a picture of it you can easily see criss-cross lines over the water-ice surface as well as the ridges, cracks, fractures, and bands.

Europa moon with margins Introduction

Science as well as science fiction professionals have long held the moon Europa in the imaginative grasp. As we have learned more about this unusual moon, science fiction has transformed into a potential reality. It seems that Europa has a rocky mantle and an iron core beneath the ocean ice shell which is estimated to be around 40-100 mi/60-150 km deep. Scientists think that there is an excellent opportunity for life to exist in the oceans below the ice.

Europa Statistics:

  • Orbits: Jupiter
  • Discovered By: Galileo Galilei
  • Discovery Date: January 8, 1610
  • Diameter: 22.2 km
  • Mass: 4.80 x 10^22 kg (65.2% Moon)
  • Orbital Period: 3.55 days
  • Orbit Distance: 671,000 km
  • Surface Temperature: – 171 degrees C

The ice that covers Europa is what gives it the reflective ability to appear so bright. Three of the moons of Jupiter, Io, Europa, and Ganymede, are orbiting in what is known as “resonance.”  Each time Ganymede completes one orbit around Jupiter, Europa has orbited twice, and Io has orbited four times.

The importance of this is that most moons will eventually change their orbit so that they are circular, however, these three moons have created a forced eccentricity due to the fact that they repetitively line up with each other at the same points in each other orbits. When this happens they give a small pull on each other that keeps them from have circular orbits.


Europa was one of the three moons discovered by Galileo Galilei in 1610. Up until this discovery, astronomers had historically thought that the Earth was the center of the universe and all celestial objects orbited around the Earth, including the sun. Galileo’s discovery changed all of that as he proved that moons orbited the planets and the planets, including Earth, orbited the sun.

Europa was named after a mythological woman who was supposed to have been abducted by the god Zeus. In Roman mythology, the named the same god Jupiter.

Formation, Structure and Surface:

Scientists have estimated that the 4 largest moons of Jupiter, also called “Galilean satellites,” Io, Europa, Ganymede, and Callisto, were more than like created from the material that remained after Jupiter condensed from the initial dust and gas cloud. The four moons are around 4.5 billion years old, which is the same age as the rest of our solar system.

Europa, like the other two moons has an elliptical orbit and the moon’s nearest side is affected by the gravitation pull from Jupiter more than its far side. The condition creates tides that relax and stretch on its surface. This constant flexing is more than likely what causes the fractures that appear on the surface.

If there is liquid water under the ice, the tidal heating may be the main reason for hypothermal activity or volcanic activity on the floor of the sea. It is due to all of these potentials that Europa may have an ocean condition that supplies nutrients that could make life possible in the ocean.

With 79 known moons, Jupiter has been referred as a mini solar system. In our own solar system, each of the planets in the inner solar system are less dense than the next one. The moons orbiting Jupiter follow the same principle.

Scientists believe that the density is directly related to the temperature. Materials that are dense, such as rock and metal condense out first while the less dense materials, such as ice, condense at greater distances where it’s colder.

The distance from Jupiter that each of the moons has will also be a determining factor on the tidal heating. Those that are closest to Jupiter will be affected by the gravitational pull the most. Io is the closest and it’s the most volcanically active object in our solar system.

Europa is covered in a layer of ice and water over a rocky, metal core; and both Ganymede and Callisto have high percentages of water ice and are at lower densities.

Europa shares some of the features of Earth: it’s believed to have an iron core, a rocky mantle, and a salt water ocean. However, there are some features on Europa that are totally different.

The most obvious one is the Europa has an ice layer that is around 10-15 mi/15-25 km thick that lays over an ocean that is nearing 40-100 mi/60-150 km deep.

Europa has one of the most unique and beautiful surface appearances. The water-ice surface has long linear fractures that criss-cross each other. It also has splotchy reddish-brown patterns all over the surface which might be salts and sulfur compounds that were mixed with water ice and affected by radiation.

Europa also has very few craters that can be seen so scientists believe that the surface is young, at around 40-90 million years old. As a comparison, Callisto’s surface is thought to be a few billion years old.

The importance of what Europa’s surface is made of may be the key to figuring out whether Europa could harbor life.

During NASA’s 1995-2203 Galileo spacecraft expedition, it made a lot of flybys of Europa. Galileo captured images of domes and pits on Europa’s surface that is believed to be caused due to the slow churning or convecting process. Convecting is a condition where the denser, cooler ice will sink to allow the less-dense, warmer ice to rise up.

The elongated, linear fractures on the surface are usually only 1-2 km wide but they can be as long as thousands of kilometers. The fractures are important to study because some have built up into ridges that are hundreds of meters tall, while others have created parallel fractures as they pull apart in multiple wide bands.

Europa Earth Moon Comparison Formation

Galileo also took images of “chaos terrain” regions which are portions of the landscape that are blocky, broken, and covered in a reddish material. It was the 2011 data that indicated that the chaos terrains might be locations where there is a collapsing surface over lakes that are lens-shaped and embedded inside the ice.

In 2014, scientists discovered that Europa may have a type of plate tectonics. So far, Earth has been the only known object in our solar system to have a dynamic crust, which is thought to be another encouragement in the development of life.

Ground-based telescopes offered scientists the theory that although the surface of Europa was mostly water ice, there was a possibility that there was slushy ice under the ice crust.

Scientists have used the Hubble Space Telescope to believe that there is a good chance that due to the constant movement, some of the ocean may be escaping into space. If this is the case, a passing spacecraft could snag samples of the ocean without ever trying to land on the surface.

Even if there aren’t any space-driven “plumes,” scientists have thought that there is an alternative way to get an ocean water sample simply by examining the areas where the ice shell distorts and brings ocean samples to the surface.

Scientists believe that underneath Europa’s ice surface is a salt-water ocean that contains twice as much water as we have with all of the oceans of the Earth combined.

Atmosphere and Magnetosphere:

Europa has only a light atmosphere, however, the discoveries of the 2013 Hubble Space Telescope research may have revealed that Europa is actively venting water into space. The discovery of the potential of active tectonic plates, make Europa the second planet to have such a condition.

The weak oxygen atmosphere is believed to be caused by charged particles from the sun hitting the surface water molecules and causing the hydrogen and oxygen molecules to break apart. The hydrogen molecules escape, leaving the oxygen molecules behind.

Europa Global Atmosphere

The Galileo mission revealed that the magnetic field of Jupiter is disrupting the space around Europa. The measurements taken imply that there is a special type of magnetic field being created inside Europa in a deeper layer of some form of under surface electrically conductive fluid.

Scientists believe that this fluid is more than likely the salt water and the magnetic field is one of the best pieces of evidence that there is an ocean under the icy surface.

Could Life Exist?

Scientists have established that in order to harbor life, a planet requires liquid water, the appropriate chemical elements, and a source of energy. Europa seems to have both the right chemical elements and a large amount of liquid water, however the energy source is the single thing that scientists haven’t been able to confirm.

Scientists have expanded their ideas of life after discovering the “extremophiles” that exist in Earth’s subterranean volcanoes and deep-sea vents.

It’s assumed that if life was found on Europa, or any of the moons, it would be more than likely in the form of microbes. Science continues to hope that if life could form independently in two different locations that orbits the same star, that there is a good possibility that it could form elsewhere in the universe.

Europa Exploration

Interesting Information:

  • A 2016 study used data to suggest that Europa produces ten times more oxygen than hydrogen. This condition is similar to the one on Earth and adds to the theory that life might be possible on Europa. In this situation, the moon might not require the kind of tidal energy that our Earth does to generate the energy needed, and instead have chemical reactions as the engine for the cycle.
  • Galileo might have actually discovered Europa a day earlier than announced. On January 7thhe had thought he had found a moon, but couldn’t be sure if it was one moon or two moons.
  • Europa was actually a mythological noblewoman and the continent of Europe was named after her. She was abducted by the Greek god Zeus and he took her to the island of Crete where she became queen.
  • The surface of Europa is the smoothest surface of any of our solar system objects. This makes sense, since the surface is covered in ice and ice is incredibly smooth.
  • While Europa might be around 4.5 billion years old, its surface is only about 20-180 million years old.
  • Europa has the highest reflectivity numbers of all of the solar system’s moons at 0.64.
  • There is a high enough radiation level on Europa to kill a human in a single day.
  • The NASA Galileo mission has given us most of the information that we know about Europa.
  • A single day on Europa is the same as 3.551 Earth days.
  • Europa only has one side that faces Jupiter and this is called being tidally-locked.


There have been five spacecraft that have been up close to Europa. A majority of what we know about Europa is thanks to the Galileo spacecraft mission. Flybys of Europa have been accomplished by the Pioneer 10, Pioneer 11, Voyager 1 and Voyager 2 spacecraft.

The Hubble Space Telescope has been focused on the study of Europa. The telescope detected a possible water plume jet on the south polar region of Europa in 2012, with other plumes being detected in 2014 and 2016.

Facts about Europa Moon for Kids:

  • Europa is almost the same size as the moon orbiting our Earth and both moons are tidally-locked around their parent planets.
  • Europa’s orbit is almost circular.
  • When Europa’s orbit nears Jupiter the gravitational pull squeezes it and causes its shape to distort. This is a kind of flexing that heats up the interior of Europa and may be what also keeps the ocean water below the ice in a fluid form.
  • The magnetic field of Europa is caused by the interaction with Jupiter’s magnetic field and may mean that there is something conductive beneath the ice.
  • The largest crater on Europa is named Pwyll.
  • A feature on Europa that some nickname “freckles” are the linae, which are jumbled lenticulae that are created by the release of meltwater due to the warm interior.

Pop Culture:

Europa was most well-known from the Arthur C. Clarke novel and later film 2010: The Year We Make Contact, when the aliens turned Jupiter in a second sun in our solar system and informed humans to leave Europa alone. The hint during the movie and at the end that new life was forming on Europa.

In the television show Futurama, Europa was featured in one of the episodes.

Europa was the setting for the Europa Report of 2013.