In the artist's impression, which is not to scale, Ganymede is shown in the foreground, Callisto to the far right, and Europa centre-right. Volcanically active moon Io is also shown, at left. The moons were imaged by NASA's Galileo spacecraft; Jupiter is seen here with a vivid aurora, captured by the NASA/ESA Hubble Space Telescope.
These moons have water. They may also contain life
02:22 - Source: CNN Business

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The European Space Agency is about to send a spacecraft to explore Jupiter and three of its largest and most intriguing moons.

The Jupiter Icy Moons Explorer mission, or Juice, was expected to lift off Thursday at 8:15 a.m. ET aboard an Ariane 5 rocket from Europe’s Spaceport in Kourou, French Guiana. But a lightning risk postponed the launch, which has been rescheduled for Friday at 8:14 a.m. ET.

Watch the launch live on ESA’s website or YouTube channel.

Weather can often cause launch delays and postponements. Specific weather criteria must be met in order for rockets to safely lift off. The James Webb Space Telescope, which launched aboard an Ariane 5 from the same location in December 2021, also faced similar delays due to adverse weather conditions around Kourou.

Once launched, the spacecraft will separate from the Ariane 5 launcher after 28 minutes. Over the course of the next 17 days, Juice will deploy its solar arrays, antennas and other instruments, followed by three months of testing and preparing the instruments.

Children from around the world shared art inspired by Juice two years ago. Ten-year-old Yaryna's artwork won the competition to become the mission's logo and it was added to the nose of the rocket carrying Juice.

Juice will take eight years to reach Jupiter, the largest planet in our solar system. During its lengthy cruise, the spacecraft will utilize some gravitational slingshots as it flies by Earth, our moon and Venus to help with the journey.

INTERACTIVE: The search for life in our solar system

Once Juice arrives at Jupiter in July 2031, the spacecraft will spend about three and a half years orbiting the gas giant and conducting flybys of three of its moons: Ganymede, Callisto and Europa. Toward the end of the mission, Juice will focus solely on orbiting Ganymede, making it the first spacecraft to ever orbit a moon in the outer solar system.

An illustration depicts Juice on its way to Jupiter.

Ganymede, Callisto and Europa are ice-covered worlds that may contain subsurface oceans that are potentially habitable for life.

Meanwhile, NASA’s Europa Clipper mission, launching in 2024, is expected to reach Jupiter in April 2030 and conduct nearly 50 flybys of Europa, eventually reaching just 16 miles (25 kilometers) above the moon’s surface.

Together, the two missions could unlock some of the biggest mysteries about Jupiter and its moons.

Up close with the king of the solar system

Exploration of Jupiter began with NASA’s Pioneer and Voyager missions in the 1970s, followed by dedicated Jupiter missions like Galileo and the Juno probe. Juno has been orbiting Jupiter and flying by some of its moons since 2016.

The Juice mission has five main objectives, including using its powerful suite of 10 instruments to characterize the three icy moons and determine whether they harbor oceans, uncover what makes Ganymede so unique and determine if the moons are potentially habitable for life.

Planetary scientists want to know how deep the oceans are, if they contain salty or fresh water and how that water interacts with the ice shell of each moon. Ganymede, Callisto and Europa also have different surfaces. Juice could reveal what kind of activity has caused some of them to look dark and cratered or paler and grooved.

Ganymede is the largest moon in the solar system, larger than Pluto and Mercury, and it’s the only one that has a magnetic field similar to Earth. Juice’s instruments can reveal the moon’s rotation, gravity, shape, interior structure and composition and peer through its icy crust using radar.

An artist's rendering depicts Juice flying by Ganymede with Jupiter in the background.

Juice will also conduct a detailed analysis of Jupiter to determine how the complex magnetic and radiation environment around this massive planet shaped its moons, as well as how Jupiter formed in the first place. Understanding more of Jupiter’s origin story can help scientists apply those findings to Jupiter-like planets found outside of our solar system.

Jupiter’s magnetic field is 20 times stronger than Earth’s and it has a harsh radiation environment, both of which impact its moons. The Juice mission was designed to unravel what takes place as Jupiter interacts with its moons, including auroras, hot spots, radio emissions and waves of charged particles.

The potential for life

Although the three moons are encased in thick ice shells, interior heating could be taking place at each moon’s core — and that warmth could make the interior oceans possible habitats for past or existing life.

Juice can search the moons for evidence of the building blocks of life, including elements like carbon, oxygen, nitrogen, iron and magnesium.

Previous missions like Galileo and Cassini, which visited Saturn and its moons, confirmed that liquid water can be found on planets and moons far away from the sun — and that water is likely to exist under the surface.

“I think Juice is a confirmation that our understanding of where to search for potential habitability has changed in the last 20 years,” said Michele Dougherty, Royal Society research professor at Imperial College London and principal investigator of Juice’s magnetometer.

Life as we understand it on Earth requires liquid water, a heat source and organic material — “and then you need those first three ingredients to be stable enough over a long enough period of time that something can actually happen,” Dougherty said.

Juice will fly by Europa twice.

“With Juice, we want to confirm there’s liquid water in these moons, confirm their heat sources. Other instruments will be able to remotely sense whether there’s organic material on the surface as well. And so it’s putting all of those ingredients together,” she said.

Surviving Jupiter

Juice’s truck-size spacecraft has been designed to survive a long journey to Jupiter — and it has to survive the extremes of the gas giant’s environment once it arrives. Two cross-shaped solar arrays will provide the spacecraft with power and lead-lined vaults protect its most sensitive electronics.

The ESA-led mission includes contributions from NASA and the Japanese Aerospace Exploration Agency. Testing and modeling of Jupiter’s radiation belts allowed engineers to prepare for what Juice will encounter.

“A key achievement of this model for us was to show that what at first seemed to be a dangerous place was not completely out of reach,” said Christian Erd, Juice spacecraft and system manager, in a statement. “Around three and a half years at Jupiter will involve the equivalent radiation exposure of a telecommunications satellite in geostationary Earth orbit for 20 years — which we have plenty of experience in managing.”

Juice can investigate why each moon, like Callisto, has a different surface.

In order to help Juice survive, its trajectory was designed to fly past Callisto 21 times but only swing by Europa twice. Europa is the closest to Jupiter and sits well within its radiation halo. Just two orbits of the moon will cause the spacecraft to experience a third of its overall radiation exposure.

Some of Juice’s instruments are shielded, while others will be exposed to the elements to probe the atmospheres of Jupiter and its moons. Multiple imagers and sensors will capture and send back data across different wavelengths of light.

Given the eventual distance between the spacecraft and Earth, it will take 45 minutes to send a one-way signal to Juice. But that’s nothing compared to the years-long wait for Juice to arrive at Jupiter.

Scientists are already anticipating the unique data Juice will return.

“I think the most critical time is the first flyby we have of Ganymede,” Dougherty said. “The first one or two flybys is when we are going to confirm the existence of an ocean.”

CNN’s Katie Hunt contributed to reporting.