The Jupiter Icy Moons Explorer (JUICE) is a pioneering interplanetary spacecraft developed by the European Space Agency (ESA) in collaboration with Airbus Defence and Space as the primary contractor. Launched on April 14, 2023, JUICE’s main objective is to investigate Ganymede, Callisto, and Europa – three of Jupiter’s Galilean moons – which are believed to harbor vast liquid water reservoirs beneath their icy exteriors, potentially rendering them habitable environments. Notably, the mission does not target Io, Jupiter’s volcanically active, non-icy moon.
Setting off on its journey on April 14, 2023, at 12:14 UTC, JUICE is scheduled to arrive at Jupiter in July 2031 after leveraging four gravity assists during its eight-year voyage. By December 2034, the spacecraft will enter orbit around Ganymede to embark on its close-up scientific mission, making history as the first spacecraft to orbit a moon other than Earth’s Moon. JUICE was chosen for the L1 launch slot of ESA’s Cosmic Vision science program, with the selection announced on May 2, 2012. The spacecraft’s operational period will coincide with NASA’s Europa Clipper mission, set to launch in 2024.
Jupiter’s Moons
The Galilean moons – Ganymede, Callisto, Europa, and Io – were first discovered by Italian astronomer Galileo Galilei in January 1610, using a small telescope. These four large moons of Jupiter were the first celestial objects found to orbit a planet other than Earth, and their discovery was crucial in supporting the Copernican view of a heliocentric solar system.
Ganymede, the largest moon in our solar system and larger than the planet Mercury, has a rocky core and an icy outer shell. Callisto, the most distant of the Galilean moons from Jupiter, has an ancient, heavily cratered surface and is thought to contain a subsurface ocean. Europa, slightly smaller than Earth’s Moon, is believed to have a vast, salty subsurface ocean beneath its icy crust, making it a prime target for the search for extraterrestrial life. Io, the innermost Galilean moon, is characterized by its extreme volcanic activity and lack of ice.
Several spacecraft have made close approaches to the Galilean moons throughout the years:
- Pioneer 10 (1973) and Pioneer 11 (1974): These two NASA spacecraft were the first to fly by Jupiter and provided the first close-up images of the Galilean moons, albeit at low resolutions.
- Voyager 1 (1979) and Voyager 2 (1979): These NASA spacecraft made closer flybys and provided more detailed images and data of the Galilean moons, revealing their diverse geology and increasing scientific interest in their potential for hosting life.
- Galileo (1995-2003): This NASA orbiter was the first spacecraft to enter orbit around Jupiter and made multiple flybys of the Galilean moons, providing high-resolution images and in-depth data on their composition, geology, and magnetic fields. Galileo’s closest approach to Europa was 206 km (128 miles), while it got as close as 264 km (164 miles) to Ganymede and 138 km (86 miles) to Callisto.
- New Horizons (2007): On its way to Pluto, this NASA spacecraft conducted a flyby of Jupiter and its moons, capturing additional data and images.
The upcoming Jupiter Icy Moons Explorer (JUICE) mission by the European Space Agency will focus on Ganymede, Callisto, and Europa, while NASA’s Europa Clipper mission, set to launch in 2024, will specifically target Europa for further study.
The Evolution of the JUICE Mission: From Concept to Reality
The JUICE mission was initially conceived as a restructured version of the Jupiter Ganymede Orbiter proposal, which was originally intended to be ESA’s contribution to the ultimately cancelled Europa Jupiter System Mission – Laplace (EJSM-Laplace). As the project evolved, JUICE became a contender for the first L-class mission (L1) of the ESA Cosmic Vision Programme, with its selection announced on May 2, 2012.
In the same month, JUICE was chosen over two other advanced proposals: the Advanced Telescope for High Energy Astrophysics (ATHENA) X-ray telescope and the New Gravitational wave Observatory (NGO), a gravitational wave detection facility. This decision reinforced ESA’s commitment to exploring Jupiter’s icy moons and their potential for hosting life.
The next milestone came in July 2015, when Airbus Defence and Space was chosen as the prime contractor for the JUICE mission. Tasked with designing and constructing the probe, Airbus Defence and Space assembled the spacecraft in Toulouse, France, paving the way for its groundbreaking journey to Jupiter’s Galilean moons.
JUICE’s Journey: Launch, Gravity Assists, and Exploration of Jupiter’s Moons
Originally slated for launch on April 13, 2023, the JUICE mission was postponed due to unfavorable weather conditions at the Guiana Space Centre. The spacecraft successfully lifted off aboard an Ariane 5 launch vehicle on April 14, 2023, at 12:14 UTC, with its solar arrays deploying shortly thereafter. ESA declared the launch a triumph.
To reach Jupiter, JUICE will utilize a series of gravity assists, including an Earth–Moon system flyby in August 2024, a Venus flyby in August 2025, a second Earth flyby in September 2026, and a final Earth flyby in January 2029. The spacecraft will also traverse the asteroid belt twice and potentially conduct a flyby of asteroid 223 Rosa in October 2029.
Upon arriving in the Jovian system in July 2031, JUICE will first execute a Ganymede flyby before entering an elongated orbit around Jupiter approximately 7.5 hours later. Gradually, the spacecraft will adjust its orbit to achieve a circular path around the gas giant. In July 2032, JUICE will perform its first Europa flyby and subsequently enter a high inclination orbit to investigate Jupiter’s polar regions and magnetosphere.
In December 2034, JUICE will establish an elliptical orbit around Ganymede, initially at a distance of 5,000 km (3,100 mi). By 2035, the spacecraft will settle into a circular orbit 500 km (310 mi) above Ganymede’s surface, conducting in-depth studies of the moon’s composition and magnetosphere.
At the mission’s conclusion in late 2035, JUICE will be intentionally deorbited and guided to impact Ganymede’s surface after expending its remaining propellant.
Unveiling the Secrets of Jupiter’s Moons: JUICE’s Scientific Objectives
The JUICE orbiter aims to conduct comprehensive investigations of Ganymede, Europa, and Callisto, with a particular emphasis on Ganymede’s potential to support life. By studying these three Galilean moons, all believed to contain subsurface liquid water oceans, scientists hope to gain valuable insights into the habitability of icy celestial bodies.
For Ganymede and, to a lesser extent, Callisto, JUICE’s primary science objectives include:
- Characterizing the ocean layers and detecting potential subsurface water reservoirs
- Conducting topographical, geological, and compositional surface mapping
- Examining the physical properties of the icy crusts
- Characterizing the internal mass distribution, dynamics, and evolution of the moons’ interiors
- Investigating Ganymede’s sparse atmosphere
- Studying Ganymede’s intrinsic magnetic field and its interactions with Jupiter’s magnetosphere
When it comes to Europa, JUICE will concentrate on identifying the chemistry vital to life, including organic molecules. The mission will also seek to understand the formation of surface features and the composition of non-water-ice materials. Additionally, JUICE will perform the first-ever subsurface sounding of Europa, determining the minimum thickness of the icy crust above the most recently active regions.
The orbiter will also conduct more distant, spatially resolved observations of several minor irregular satellites and the volcanically active moon Io, further expanding our understanding of Jupiter’s diverse family of moons.
“We are ready to steer one of the most complex missions ESA has ever flown to adventures in the jovian system,” says Angela Dietz, deputy spacecraft operations manager. “From flybys of Jupiter’s moons over a period of two-and-a-half years, to the immense challenge of switching orbits from massive Jupiter to orbiting Ganymede, we’ll be solving challenges at mission control that have never been done before.”
The Juice Equipment
JUICE is equipped with two monitoring cameras situated on the spacecraft’s ‘body’ to document various deployments. These cameras capture 1024 x 1024 pixel images, which are then lightly processed and undergo preliminary color adjustments.
Once JUICE reaches the Jovian system in 2031, a dedicated scientific camera will be employed to capture high-resolution images of Jupiter and its icy moons.
Juice Monitoring Camera 1 (JMC1) is positioned at the front of the spacecraft, capturing images diagonally upward. Its field of view includes a portion of one solar array and will eventually record deployed antennas.
Juice Monitoring Camera 2 (JMC2) is installed on the top of the spacecraft and is designed to observe the multi-stage deployment of the 16-meter-long Radar for Icy Moons Exploration (RIME) antenna. RIME is an ice-penetrating radar that will probe the subsurface structure of Jupiter’s large moons remotely.
Currently, RIME is in a stowed configuration, but it will gradually unfold in the coming days, with images taken to document the full deployment process.
The monitoring cameras will also remain active during various mission operations, including gravity assist flybys of the Moon, Earth, and Venus en route to Jupiter.
Special Note about featured image:
Jupiter has 79 known moons, with the four largest being the Galilean moons: Ganymede, Callisto, Io, and Europa. In terms of mass, the Galilean moons make up more than 99.9% of the total mass of Jupiter’s entire moon system. Here are the percentages of the Galilean moons’ masses relative to each other:
- Ganymede: Approximately 2.02 x 10^23 kg (mass percentage ~ 46.0%)
- Callisto: Approximately 1.075 x 10^23 kg (mass percentage ~ 24.5%)
- Io: Approximately 8.93 x 10^22 kg (mass percentage ~ 20.4%)
- Europa: Approximately 4.8 x 10^22 kg (mass percentage ~ 10.9%)
Please note that these percentages are approximate and calculated based on the masses of the four Galilean moons. The remaining 75 smaller moons account for less than 0.2% of the total mass of Jupiter’s moon system.