Meet the Solar System: Europa

How well do you know your astronomical neighborhood? Let’s go on a trip through our solar system and explore the weird, the wild, and the beautiful all around us. Today, we are learning all about Europa.

Where is it?

Europa is one of Jupiter’s moons, orbiting Jupiter at about 417,000 miles (671,000 kilometers) from the planet. Light from the Sun takes about 45 minutes to reach Europa. Because of the distance, sunlight is about 25 times fainter at Jupiter and Europa than at Earth.

What’s up with the name?

Europa is named for a woman who, in Greek mythology, was abducted by the god Zeus – Jupiter in Roman mythology. Europa was a princess of Phoenecia and the mother of King Minos of Crete.

Zeus appeared to Europa as a white bull on the beach. When Europa climbed on the bull’s back, it plunged into the sea and swam away with her. Eventually, the two touched down on the island of Crete.

It’s there that Europa became the island’s first queen and, thus, had the future King Minos. Later, Minos would turn cruel and end up with the Minotaur as his son, building a labyrinth beneath his palace to hide the monster.

Whether its fitting that a moon of Jupiter, which is the Roman name for Zeus, is named after a woman Zeus kidnapped and isolated, who’s to say?

Who “discovered” it?

Our old friend Galileo Galilei discovered Europa on Jan. 8, 1610. It’s been a minute since we talked about Galileo, but it’s not surprising that he was the first to record and name Europa. His telescopes and observations were integral to our new understanding of the solar system.

That’s also why Jupiter’s four largest moons, including Europa, are known as Galillean moons.

What’s it made of?

Like our planet, Europa is thought to have an iron core, a rocky mantle, and an ocean of salty water. Unlike Earth, however, Europa’s ocean lies below a shell of ice probably 10 to 15 miles (15 to 25 kilometers) thick, and has an estimated depth of 40 to 100 miles (60 to 150 kilometers). While evidence for an internal ocean is strong, its presence awaits confirmation by a future mission.

Can we live there?

You know that possible internal ocean we just mentioned? It’s very important for the possibility of life on Europa. We may not be able to live there. But there may be life on Jupiter’s moon.

Life as we know it seems to have three main requirements: liquid water, the appropriate chemical elements, and an energy source.

Astrobiologists – scientists who study the origin, evolution, and future of life in the universe – believe Europa has abundant water and the right chemical elements, but an energy source on Europa has been difficult to confirm. On Earth, life forms have been found thriving near subterranean volcanoes, deep-sea vents, and other extreme environments. These “extremophile” life forms give scientists clues about how life may be able to survive beneath Europa’s ice shell.

If we eventually find some form of life at Europa (or Mars or Enceladus for that matter), it may look like microbes, or maybe something more complex. If it can be demonstrated that life formed independently in two places around the same star, it would then be reasonable to suspect that life springs up in the universe fairly easily once the necessary ingredients are present, and that life might be found throughout our galaxy and the universe.

How long is a year there? What about a day?

Europa orbits Jupiter every 3.5 days and is locked by gravity to Jupiter, so the same hemisphere of the moon always faces the planet. Jupiter takes about 4,333 Earth days (or about 12 Earth years) to orbit the Sun (a Jovian year). Jupiter’s equator (and the orbital plane of its moons) are tilted with respect to Jupiter’s orbital path around the Sun by only 3 degrees (Earth is tilted 23.5 degrees). This means Jupiter spins nearly upright so that the planet, as well as Europa and Jupiter’s other dozens of moons, do not have seasons as extreme as other planets do.

Has NASA sent any missions there?

There have been a few NASA missions to Jupiter that have studied Europa briefly. NASA’s Galileo spacecraft explored the Jupiter system from 1995 to 2003 and made numerous flybys of Europa.

Soon, though, NASA will be launching a mission specifically to the moon called the Europa Clipper. The Europa Clipper spacecraft will conduct a detailed survey of Jupiter’s moon Europa to determine whether the icy moon could harbor conditions suitable for life. The spacecraft, in orbit around Jupiter, will make about 40 to 50 close passes over Europa, shifting its flight path for each flyby to soar over a different location so that it eventually scans nearly the entire moon.

After each flyby, the spacecraft will send its haul of data back to Earth. The time between flybys will also give scientists time to study the data and consider adjusting the timing and trajectory of future flybys if they find regions that spark curiosity and need more study.

Can I see it from here?

Yes! Europa is one of four Jovian moons you can see with a telescope. When looking at Jupiter, Europa is usually the closest moon to the planet. The other four that are visible are Io, Callisto, and Ganymede.