Juice Mission Launches to Explore Jupiter and Its Icy Moons

The spacecraft will investigate oceans that might lie beneath the moons’ surfaces and study whether they could support life

A rocket lifting off from Earth
The rocket carrying the Jupiter Icy Moons Explorer launches from French Guiana on April 14.  JODY AMIET / AFP via Getty Images

The Jupiter Icy Moons Explorer, or Juice for short, began its long journey toward the fifth planet from the sun on Friday morning. The European Space Agency’s (ESA) uncrewed spacecraft launched from French Guiana at 8:14 a.m. Eastern time.

Juice will study Jupiter and three of its largest moons, Ganymede, Callisto and Europa. Scientists hope the spacecraft can learn more about large oceans of water that might lie beneath the lunar surfaces and offer hints at whether or not any of the moons have ever supported life.

“The main goal is to understand whether there are habitable environments among those icy moons and around a giant planet like Jupiter,” Olivier Witasse, a planetary scientist and Juice team member, said at a press conference last week, per Space.com’s Mike Wall.

To take off toward its Jovian destination, Juice needed perfect conditions. The spacecraft had only a one-second launch window to get off the ground, in which it could get to Jupiter with the least fuel. Originally, its launch was scheduled for Thursday morning, but a risk of lightning pushed the takeoff to the same time on Friday, according to the Guardian’s Ian Sample. Had the conditions not been right Friday morning, the mission would have had more chances to leave Earth—in a one-second window every day for the rest of April.

Juice’s successful launch kickstarts its eight-year odyssey to Jupiter. To get there, the spacecraft will perform several flybys of Earth and Venus that will propel it deeper into the solar system with the help of the planets’ gravity. First, Juice will swing around the moon in August 2024—then around Earth only 1.5 days later. Next, it’s scheduled to fly by Venus in August 2025, then pass by Earth two more times—in 2026 and 2029—before reaching Jupiter in July 2031, according to an ESA statement.

Once it arrives at the gas giant, Juice will spend the next 3.5 years performing 35 flybys of three of the planet’s moons, all of which are thought to contain water. In orbit around Jupiter, it will pass the cratered moon Callisto 21 times and soar by Europa twice.

Finally, in December 2034, Juice will enter into orbit around Ganymede, Jupiter’s largest moon, where it will remain for nine months. The plan is to then crash the spacecraft into Ganymede at the mission’s end in 2035, unless researchers determine this might contaminate the moon, per the New York Times’ Jonathan O’Callaghan.

NASA’s Pioneer and Voyager missions examined Jupiter up close in the 1970s, and the agency’s Juno orbiter is currently studying the planetary system. These and other past studies have helped researchers build our understanding of Jupiter and its moons. Scientists think that Europa, for example, has a salty ocean and is one of the best places to search for life in the solar system, according to NASA. In 2030, NASA’s Europa Clipper mission—currently slated for launch next year—is planned to perform nearly 50 flybys of that moon, per CNN’s Ashley Strickland.

One of the primary goals of the Juice mission is to learn more about the oceans Jupiter’s moons might have. “If I had one objective to highlight, it is the need to know more about the liquid water underneath the surface of the icy moons,” Witasse said at the press conference, per Space.com.

Juice will map the moons’ topography, which could provide a key clue about whether oceans exist there: The larger the deformations on a moon’s surface, caused by the gravity of Jupiter and its other moons, the more likely there is to be a liquid beneath it, rather than a solid, per Nature News Davide Castelvecchi.

Scientists also hope to learn how deep the oceans might be, whether they are salty or fresh water and how they interact with the moons’ icy surfaces, writes CNN. The spacecraft’s ten instruments will study the moons’ atmospheres, as well as the magnetic field and radiation around Jupiter.

And, of course, the mission will examine whether each of the orbs are hospitable for life.

“For habitability, you need liquid water, a heat source and organic materials,” Michele Dougherty, a space physicist at Imperial College London who worked on the Juice mission, tells the Times. “If we confirm or deny those three things, we’ve done what we said we were going to do.”

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