Fascinating Facts About Jupiter’s Moon Europa


Europa is one of the four Galilean moons of Jupiter, in addition to Io, Ganymede, and Callisto. It’s also one of the most talked about moons, as it has made several headlines over the years for its interesting characteristics, discovered through observation from various spacecrafts.

A major component in table salt has been discovered on Europa, as well as the real possibility of life being able to survive there – some even say that there’s a better chance of life being found on Europa than on Mars. From the size and the location of the moon, to who actually discovered it, let’s take a look at some very interesting facts that you may not know about Europa. 

9. Age, Location, And Size

Europa is approximately 4.5 billion years old – around the same age as the planet it orbits, Jupiter. It is the smallest of the Galilean moons with a diameter of 1,900 miles. In comparison, Europa is smaller than Earth’s moon, but bigger than Pluto.

As for its location in our Solar System, Europa’s average distance from the sun is around 485 million miles. Since it’s the second innermost of Jupiter’s moons, it orbits at a distance of 414,000 miles. To get a better understanding of Europa’s distance from Jupiter, Earth’s moon has an average distance of almost 239,000 miles away from us. And just like our moon, Europa also has only one side that continuously faces Jupiter. Additionally, it takes Europa three and a half Earth days to complete a full orbit around Jupiter. 

8. Galileo Discovered Europa In 1610

On January 8, 1610, Galileo Galilei discovered Europa. That’s why the moon — along with the three others — are named the Galilean moons. The famous Italian astronomer used a telescope (which he also designed) to study the “three fixed stars, totally invisible by their smallness.”

He noticed that the “stars” had changed their positions and one of them had completely disappeared as it was positioned behind Jupiter. Just a few days later, he realized that they were not stars, but in fact moons that were orbiting the giant gas planet. Not long after that, he discovered the fourth of the Galilean moons.

Of Jupiter’s 79 moons, the four Galilean moons are the largest. In fact, Io, Europa, Ganymede, and Callisto are some of the largest moons in our solar system – ranking fourth, sixth, first, and third biggest, respectively. Earth’s moon is ranked fifth. 

7. Origins of Europa’s Name

 According to Greek mythology, Europa was a Phoenician noblewoman and the daughter of the king of Tyre. She ended up being abducted by Zeus who, in order to try and seduce her, transformed himself into a spotless white bull. After she had adorned the bull with flowers, she got on its back and they rode off to the island of Crete. Zeus transformed back into himself once they arrived on Crete, and seduced Europa. She became the queen of Crete and she and Zeus had many children together.

It was the German astronomer Simon Marius who first proposed that the moons be named after the lovers of Zeus. Marius claimed that he discovered the moons prior to Galileo, although it was never proven to be true. Galileo, on the other hand, called the moons the Medicean planets after the Medici family. The moons were officially given their names in the 19th century. 

6. Extremely Cold Environment

Europa is made of silicate rock with an iron core and rocky mantle – quite similar to Earth. Also like Earth, Europa is believed to have tectonic plates. This is quite stunning, as it was previously thought that Earth was the only planetary body in our solar system to have a dynamic crust, which scientists say is important in the evolution of life. On the other hand, unlike Earth, it is believed that the rocky interior of Europa has liquid water and/or ice surrounding it that could be around 50 to 105 miles thick.

Europa has a very thick icy crust that creates a light reflectivity of 0.64, making it one of the most reflective moon surfaces in our entire solar system. And it’s very cold to say the least, as the temperature at the moon’s equator does not rise above -260 degrees Fahrenheit. It’s even colder at the moon’s poles, as the temperatures don’t get any warmer than -370 degrees Fahrenheit.

5. Many Satellites Have Studied Europa

Numerous spacecrafts have flown by Europa in order to study the fascinating moon. The spacecrafts that conducted short-term studies on the moon are the Pioneer 10 (flew by in 1973), Pioneer 11 (flew by in 1974), Voyager 1 (flew by in 1979), and Voyager 2 (also flew by in 1979). The Voyager 2 made the discovery of brown stripes, indicating that there were cracks on the surface of the moon.

The Galileo spacecraft conducted a long-term mission of Jupiter and its moons from 1995 to 2003, making the most famous and biggest discovery in the moon’s history of a potential subsurface ocean beneath its icy crust.

NASA and the European Space Agency plan to go back to study Europa, as well as other moons, in the 2020s. The Europa Clipper is scheduled to conduct 40 to 45 flybys of Europa in the 2020s in order to get evidence of the water plumes that have been previously spotted. The JUpiter ICy moons Explorer (or JUICE) is also expected to leave Earth sometime in the 2020s (they’re aiming for the year 2022) and travel to Europa to search for organic molecules that could indicate life, as well as determine how thick the crust is. That mission is expected to last at least three years. 

4. Extremely High Radiation Levels

There’s enough radiation on Europa to kill a human in just one day. With the discovery of water plumes, scientists want to gather more evidence, but that may not be so easy. The high levels of radiation coming from Jupiter’s magnetosphere could destroy anything that reaches Europa’s surface.

Tom Nordheim, who is part of a team from NASA’s Jet Propulsion Laboratory in California, said, “When we examine materials that have come up from the subsurface, what are we looking at? Does this tell us what is in the ocean, or is this what happened to the materials after they have been radiated?”

The lander may have to dig or drill into the icy crust to get a better and non-radiated sample. And depending on where they are on the moon, the drilling depths differ. For example, the highest radiation levels are at the equator, so if the lander decides to dig for a sample there, it would have to drill between 4 and 8 inches. If it drills in a lower-radiation zone, like Europa’s poles, it would only have to drill down 0.4 inches to get a fresh sample. This, however, also poses a big concern for the spacecrafts as they may get destroyed by the extreme radiation if they get too close to the moon. 

3. Table Salt Compound Discovered On Europa

By using visible-light spectral analysis, scientists have discovered sodium chloride on Europa’s surface. Table salt is almost entirely made up of sodium chloride and it’s the main component in sea salt. This suggests that the subsurface ocean on Europa may be similar to the oceans found right here on Earth.

While it was first believed that the compound discovered on the Europa’s surface was magnesium sulfate, the high spectral resolution data revealed that it couldn’t have been that since the majority of sulfate salts had certain absorptions that should have been seen, but the characteristics weren’t observed.

Since sodium chloride can’t be detected in an infrared spectrum, scientists conducted tests on ocean salts from Earth that were introduced to the same Europa-like conditions and they found that the compound turned yellow – the same color that was observed on the visible spectrum. “Sodium chloride is a bit like invisible ink on Europa’s surface. Before irradiation you can’t tell it’s there, but after irradiation the color jumps right out at you,” explained scientist Kevin Hand. This could mean that the moon’s ocean floor may possibly be hydrothermally active. 

2. Subsurface Ocean

In the late 1970s and early 1980s, the Voyager 1 and 2 spacecrafts took pictures of Europa that showed significant and very interesting details. Its surface was brighter than our own moon’s. There were several bands and ridges on the surface, and there weren’t many craters, mountains, or tall cliffs. All in all, it had a very smooth surface compared to other icy moons in our solar system.

The pictures revealed dark icy material that was coming through the opened cracks on the surface, indicating that there had been activity at some point. Since the moon is 4.5 billion years old, it should have tons of impact craters on its surface, but surprisingly there were only a handful that were spotted by the spacecrafts. This suggests that something had erased the craters and that perhaps a layer of liquid water or even warmer ice was present between the crust and the deeper interior of the moon. With that being said, it is now believed that the surface of the moon is only about 20 to 180 million years old.

Europa’s interior may still be warm even to this day, suggesting a subsurface ocean of salty water. Several different research teams noticed possible water plumes jetting to the surface of the moon’s south polar region, suggesting that there could very well be liquid water under Europa’s icy surface.

In fact, NASA revealed that Europa has three pieces of evidence that strongly support a subsurface ocean. According to magnetometer surveys conducted by the Galileo spacecraft, an induced magnetic field close to the surface of the moon indicates that a large body of salty water resides at a depth of 20 miles or less. Second, the ridges, bands, fractures, and multi-ringed impact structures on the moon indicate that there is something mobile below the surface. And finally, the fractures and ridges on Europa are similar to the tectonic plates found on Earth which suggests that something mobile is allowing the crust to move.

1. There May Be Life on Europa

Since there’s a very real possibility that there may be a subsurface ocean beneath the surface, scientists have ranked Europa as being one of the best locations in our solar system to potentially have life. In order to have life, there needs to be three important factors: liquid water, chemical building blocks, and a source of energy – all three of things are believed to be present on Europa.

A subsurface ocean up to 100 kilometers (or 62 miles) deep is believed to exist on Europa, containing dissolved ions (specifically magnesium, sodium, potassium, and chlorine) that many organisms need in order to survive.

Ice and other materials that are found on Europa’s surface, mixed with Jupiter’s radiation, can create building blocks for life, such as oxygen, hydrogen peroxide, sulfur dioxide, and carbon dioxide.

Since the gravitational pull from when it orbits around Jupiter makes the moon have stronger and weaker forces, it creates friction inside of the moon that results with it heating up. The increased and decreased gravitational forces that cause the inside of the moon to heat up could be the reason why the subsurface ocean remains in liquid format. And since organisms have been found in the subglacial lakes of Antarctica, there’s a real possibility that they could also survive on Europa.

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