Jupiter’s moon Europa is NASA’s next search for potential life

Where there’s water, there’s life. At least on Earth. So, do the same rules apply off-world? We sent the Perseverance rover to an ancient Martian lakebed to gather clues of past life. By that logic, could a probe to a presumed icy ocean on Jupiter’s moon, Europa, find potential for current life?

That’s the hope propelling the Europa Clipper, the largest NASA spacecraft developed for a planetary mission and the first detailed science investigation of Europa. The craft is slated to launch by Nov. 6 from Kennedy Space Center (KSC) aboard a SpaceX Falcon Heavy rocket, commencing a 1.8-billion-mile journey towards a Jovian orbit in April 2030. There it will spend four years, 80 circumnavigations of Jupiter, and 49 low-altitude flybys of Europa surveying conditions that might make her suitable for life.

The $5.2 billion mission has been a massive undertaking, involving 11 years of development and more than 4,000 individuals. A joint project between Johns Hopkins University’s Applied Physics Laboratory and NASA’s Jet Propulsion Laboratory (JPL), roughly 1,000 people currently work on the operation, including more than 220 scientists from the U.S. and Europe.

Why Europa?

The fourth largest of Jupiter’s 95 moons and roughly the size of ours, Europa presents strong evidence for a saltwater ocean some 40 to 100 miles deep beneath a layer of ice 10 to 15 miles thick. It’s thought to contain twice the liquid water of Earth’s oceans, making it one of the best places beyond our planet to look for a habitable microbial environment. (Even in spacesuits, humans wouldn’t last a day in the intense radiation.)

Clipper carries nine instruments and a gravity experiment to accomplish three main goals: determining the thickness of the moon’s icy shell and its surface interactions with the ocean below, investigating its composition, and characterizing its geology. A suite of cameras, spectrometers, and a thermal imager operating in visible, infrared, and ultraviolet light will detail Europa’s surface and atmospheric components, temperatures and topography, geologic movement, and plumes of water vapor. Magnetometers tracking variations in Jupiter’s magnetic field will determine the existence of Europa’s ocean, its depth, salinity, and—in concert with a gravity experiment and radar—the thickness of its icy crust. A plasma instrument will study the density, temperature, and flow of charged particles nearby.

“There’s very strong evidence that the ingredients for life exist on Europa, but we have to go there to find out,” says deputy project scientist Bonnie Buratti. “We’re not a life detection mission, we’re just looking for the conditions for life: water, chemicals, specifically organic compounds, that can serve as food for any primitive organisms, and finally, energy. If there is life on Europa, it will be underneath the ocean, so we wouldn’t be able to see it.”

The seven-body problem

The Clipper runs 100 by 58 feet, slightly larger than a basketball court—it’s size due to the massive solar arrays needed to capture the little sunlight reaching Jupiter. Ninety minutes after launch, the arrays will unfurl from the spacecraft in a 40-minute process, before the craft embarks on a challenging trajectory to Jupiter.

Although the average distance to Jupiter is 480 million miles, the Clipper will take the scenic route around Mars and back around Earth, using the gravity from both planets like a slingshot to add speed. Arriving at Jupiter, Clipper will fire its engines to enter her orbit and use solar energy to power its science instruments, electronics, and substations.  

“You’ve heard of the three-body problem that’s been popularized by a recent TV show; Jupiter’s essentially a seven-body problem,” says Europa Clipper project manager Jordan Evans. “You’ve got Jupiter, the sun, the spacecraft, and the four Galilean moons. There’s no other place in the solar system that is so dynamically complex in terms of gravity.”

Too hot to handle

But that was the starter kit. Navigating Jupiter’s radiation—the most powerful in the solar system after the sun—became the mission’s biggest challenge. And nearly its downfall.

Jupiter’s magnetic field is 20,000 times stronger than Earth’s and spins in time with the planet’s rotation, capturing and accelerating charged particles to create powerful and damaging radiation belts. It’s akin to flying the Clipper through a giant particle accelerator. That environment prevents the Clipper from orbiting Europa, despite encasing its electronics in a specially designed vault.

Instead, it will make a wide orbit of Jupiter, spending less than a day flying by Europa—swooping as low as 16 miles above its surface to gather data—before moving far enough away from the planet and its radiation onslaught for two to three weeks to enable its electronics to recover. During each flyby, the science instruments will operate simultaneously, with scientists combining the data for a complete picture.

Fly in, grab the science data, fly out, process the data, send it back to Earth, and repeat. “Each of those flybys, the surface of the spacecraft is exposed to the equivalent of a few million chest X-rays,” says Evans. “And yet the Europa Clipper instruments have to be sensitive enough to gather the critical information that scientists need to learn about the moon.”

And this is where things almost went south. Last spring, shortly after the Clipper moved from a JPL clean room to KSC, JPL engineers learned that the same transistors used on the Clipper fell short of the radiation-hardness standards in an unrelated satellite mission. Transistors are miniature semiconductors that amplify and switch electrical signals. Failing to resolve the issue by the launch window would push back the mission by 13 months or cancel it if not at all. After a nail-biting four months of testing, NASA gave the final clearance only last month.

“I began [the mission] thinking I had a really solid appreciation of how long and difficult the road ahead was going to be—and I was completely and utterly wrong about that,” says Europa Clipper program scientist Curt Niebur. “It was much harder than I anticipated, and it got harder with each year. There was no harder year than this past year, culminating in the transistor problems that we’ve recently overcome.”

Greetings from Earth

The Europa Clipper is also continuing a NASA tradition of gracing its spacecraft with inspirational messages and images from Earth. Here, its triangular metal vault plate sealing the vault doubles as a small art gallery. Engravings on both sides depict water as the shared connection of humanity, Earth and Europa, and potentially extraterrestrial life.

The outward side features audio waveforms of people saying the word “water” in 103 spoken languages extending from an American Sign Language symbol for water. (You can listen to those pronunciations on this waveform generator.) The reverse sports a poem by U.S. Poet Laureate Ada Limón and a microchip with some 2.6 million names submitted by the public. (I submitted my pet snail, Flash.) There’s also a drawing of the Jovian system; a tribute to the late planetary scientist Ron Greenley, who helped lay the foundation for the Clipper; the Drake Equation, which estimates the likelihood of advanced alien civilizations; and “Water Hole” radio frequencies that are theorized best for interstellar communication. If you can’t make it to Jupiter, you can see a replica in JPL’s Blended Worlds: Experiments in Interplanetary Imagination exhibit that’s part of Getty’s PST Art: Art and Science Collide arts event across Southern California.

The mission’s end will see Clipper potentially crash into Ganymede, another Jupiter moon. Before so, the mission will overlap with that of ESA’s JUICE (Jupiter Icy Moons Explorer) which will be in the neighborhood studying Ganymede, giving the two space agencies an opportunity for collaboration there.

“Right now, we’re searching for whether Europa is habitable or not,” says Gina DiBraccio, acting director of NASA’s Planetary Science Division. “Depending on what we see, we might choose to send a mission back to actually determine if life currently exists.”