Out of the four Galilean moons, Europa is the smallest, but it is also the sixth-largest moon in the Solar System. It was named after the Phoenician mother of King Minos of Crete and lover of Zeus.
What sets Europa apart from the other Galilean moons, or the vast majority of satellites in general, is the fact that it may harbor life since optimal conditions for life to evolve are present.
Today, we are going to present to you some interesting pieces of information about Jupiter’s moon, Europa, and what sets it apart from other celestial objects. With that being said, we are going to answer some questions such as:
- Why is the moon Europa so special?
- Can Europa harbor life?
- What are some characteristics of Europa?
- How did Europa form?
- How was Europa discovered?
- How many missions were sent to Europa? Are there any more planned?
Why is the moon Europa so special?
Europa’s atmosphere is very thin, composed primarily out of oxygen. Its surface is very smooth, the smoothest of any known solid object in the Solar System [1].
This apparent youth of the smoothness of its surface led to the hypothesis that a water ocean exists beneath. This could conceivably harbor extraterrestrial life.
This makes Europa one of the most closely studied bodies in the Solar System. It probably has the highest chances of either having or developing life.
Ground-based telescopes were used in determining that Europa’s surface is made mostly out of water ice, and scientists have found strong evidence that an ocean of liquid water may be present underneath the surface.
Spacecraft and space telescope observations have also pointed towards this. Scientists believe that Europa’s ice shell is 15 to 25 km /10 to 15 mi thick, floating on an ocean 60 to 150 km/ 40 to 100 mi deep.
Though this moon is only one-fourth the diameter of Earth, its ocean may contain twice as much water as all of Earth’s oceans combined. A spacecraft could be able to take a sample of this water and analyze it properly.
Can Europa harbor life?
As far as we know, life seems to have three main requirements:
- Liquid water
- The appropriate chemical elements
- Energy source
Scientists have directly detected water vapor for the first time above Europa’s surface in 2019. The team measured the vapor using a spectrograph that measures the chemical composition of planetary atmospheres through the infrared light they emit or absorb.
It is possible that thin plumes of water are being ejected above Europa’s surface; this indicates that the moon may be geologically active.
If these plumes do exist, a spacecraft could analyze and study the material’s composition to determine whether Europa’s ocean is hospitable for some forms of life, without the need for the spacecraft to land on its surface.
On the other hand, astrobiologists believe the moon has abundant water and the right chemical elements; however, the problem is the energy source that hasn’t yet been determined.
However, on Earth, some life forms thrive near subterranean volcanoes, deep-sea vents, and other extreme environments. These life forms can give clues about how life may be able to survive beneath Europa’s icy shell.
Thus, the life forms on Europa may be microbial or possibly more complex.
What are some characteristics of Europa?
Europa has an equatorial diameter of 3,100 km/ 1,940 mi; it is about 90% of the size of our Moon. Its water ice surface reflects 5.5 times the sunlight than our Moon does [2].
Europa orbits Jupiter at around 671,000 km/ 417,000 mi from the planet, which itself orbits the Sun at a distance of about 780 million km/ 500 million mi.
Light from the Sun reaches Europa in about 45 minutes, and due to the distance, the light is 25 times fainter there than on Earth. Europa orbits Jupiter once every 3.5 days, and it is tidally locked to the planet, meaning it always shows just one side of it towards Jupiter.
Io, Europa, and Ganymede are in a resonance – every time Ganymede orbits Jupiter once, Europa orbits twice, and Io orbits four times. These gravitational tugs keep their orbits from becoming circular.
Since Europa’s orbit is elliptical, its distance varies, and its near side feels Jupiter’s gravity stronger than its far side. This creates tides that stretch and relax the moon’s surface.
In turn, the moon’s surface fractures. If indeed there is an ocean beneath Europa’s surface, the tidal heating could also lead to volcanic or hydrothermal activity on the seafloor, supplying nutrients that may make the ocean suitable for life.
How did Europa form?
All the Galilean moons likely formed out of leftover material after Jupiter condensed from the initial cloud of gas and dust surrounding the Sun, in the early history of the Solar System [3].
All four moons likely have the same age as the rest of the Solar System, about 4.5 billion years old. The four moons are sometimes referenced as a “mini solar system” since they formed similarly to how Earth and the other planets formed from gas and dust left over from when the Sun formed.
Another similarity is the fact that each planet in the inner system is less dense than their neighbor – Mars is less dense than Earth, which is less dense than Venus, and so on.
The Galilean moons follow the exact same principle. The farther they are from Jupiter, the less dense they are. This distance also dictates the tidal heating of the moons.
Io is the closest to Jupiter, and as such, it is so heated that it became the most volcanically active body in the Solar System. Europa, on the other hand, has a layer of ice and water on top of a rocky and metal interior.
How was Europa discovered?
The person most credited for the discovery of Europa is Galileo Galilei. Using a low-powered telescope, Galileo discovered Europa on January 8th, 1610.
Some believe he discovered the moon on January 7th, but he couldn’t distinguish it from Io, another moon of Jupiter. Galileo’s discovery had both astronomical and religious impacts [4].
In that era, it was believed that everything revolved around the Earth. Galileo’s observations concluded that not everything revolved around the Earth, as he noticed that Venus goes through similar phases as our Moon. The discovery of Jupiter’s moons also helped in this.
All the moons were named after Jupiter’s lovers or victims, depending on one’s point of view.
How many missions were sent to Europa? Are there any more planned?
Since Europa’s characteristics are conducive towards supporting life, the moon has received much attention and continues to do so to this day. Europa has been subjected to many missions, and even more are considered for the future, here is a list:
- 1973 – Flyby – Pioneer 10 – Observed variations in brightness.
- 1974 – Flyby – Pioneer 11 – Other variations were noticed.
- 1979 – Flyby – Voyager 1 – Insights on Jupiter’s moon system gravitational interactions.
- 1979 – Flyby – Voyager 2 – Brown stripes suggesting cracks in the icy surface were noted.
- 1995-2003 – Orbiter – Galileo – Uncovered strong evidence for the presence of an underground ocean.
- Proposed for the 2020s – Flyby – Europa Clipper – The primary goal will be to find evidence of the apparent plumes that were spotted.
- Proposed for the 2020s – Orbiter – JUICE – The purpose of this mission is to look for molecules, such as organic ones that are associated with life-giving processes.
With each new mission, we learn more and more about the beautiful Galilean moon Europa. The Galileo spacecraft is possibly the most successful on the list [5].
It measured how Jupiter’s magnetic field was disrupted in the space around Europa. The data implied that a particular type of magnetic field is being created within Europa by a deep layer of electrically conductive fluids beneath the surface.
The presence of a global ocean likely creates this magnetic signature, and this is currently the best evidence for its existence.
Did you know?
– Some claim that the German astronomer Simon Marius discovered Europa at the same time as Galileo; however, he did not announce his discovery.
– Galileo called the moons the Medicean planets in honor of the Medici family.
– Though the moon is old, its surface has been dated to be between 20 to 180 million years old.
– The radiation on Europa is so high that it would kill a human in just one day.
