ESA’s JUICE set to explore Jupiter’s mysterious moons

​Astronomers have always been fascinated by the gas giant Jupiter. A planet over 1000 times the size of Earth with 63 natural moons, 4 of whom are nearly as big as planets themselves, Jupiter and its moons are considered to be a mini solar system and are popularly known as the Jovian system. 

Jupiter's massive size and gravitational pull have led to some unique features on the planet's 4 largest moons, Io, Europa, Ganymede, and Callisto. They are also known as the Galilean moons as they were discovered by Galileo Galilei in January 1610 and were the first satellites found to orbit a planet other than Earth. While Io is known to be extremely dry with over 400 active volcanoes, scientists believe that Europa, Ganymede and Callisto have subsurface oceans below their icy surfaces which may harbor life.

​​Each image shows Jupiter's appearance at a range of different wavelengths. Image credit: NASA/ESA

The possibility of large life supporting oceans of water, especially on Europa and Ganymede has led to a flurry of exploration proposals from major space agencies worldwide. The most prominent among them is the European Space Agency's Jupiter Icy Moon Explorer Mission (JUICE).

​JUICE is the ESA's first Large class (L-Class) mission which will be launched in June 2022. The spacecraft will be launched on an Ariane 5 rocket and is expected to have a cruise duration of 7.6 years and will reach the Jovian system by 2030. Juice will spend over 3.5 years in the Jovian system, studying Jupiter and its large moons Ganymede, Castillo and Europa finally orbiting Ganymede in 2033. 

The aim of JUICE (JUpiter ICy moon Explorer) is to provide the most comprehensive exploration of the giant planet and, in particular, of its moons; supposedly hiding habitable zones under their icy crusts. Video credit: ESA

JUICE will carry a payload of 10 sensitive instruments and one experiment developed by scientific teams from 15 European countries, the United States and Japan. These payloads will include cameras and spectrometers, a laser altimeter and an ice-penetrating radar. The mission will also carry a magnetometer, plasma and particle monitors, and radio science hardware among other instruments. NASA will be contributing one Ultraviolet Spectrometer and will fund 2 more instruments aboard the solar powered JUICE spacecraft. The spacecraft will also carry a high gain antenna, approximately 3 meters (9.9 feet) in diameter which will provide daily data downlink of 1.4 Gb with a maximum signal round trip time of up to  1h 46 m.

These instruments represent the most sophisticated and state of the art scientific package that will travel to the outer reaches of the solar system. JUICE's payloads will allow it to complete all its scientific objectives which will include a detailed study of Jupiter's atmosphere and magnetosphere and a close look at the surface and interior of the three icy moons, Ganymede, Europa and Callisto, looking for evidence of subsurface liquid oceans. The last stage of the mission will involve the spacecraft orbiting Ganymede for 8 full months and perform a detailed analysis of its environment. The mission will end with the JUICE spacecraft impacting the surface of Ganymede.

Combined NASA ESA Jupiter system mission. Video credit: Space Telescopes 

The JUICE mission will concentrate on 2 major themes. They are detailed below.

The Jupiter system as an archetype for gas giants

Jupiter can be considered to be an archetype for the gas giants of our solar system and large exoplanets which orbit other stars.The mission will study Jupiter, its atmosphere and magnetosphere on a detailed basis. 

Jupiter's atmosphere will be investigated from the cloud tops to the thermosphere and its structure, dynamics and composition will be studied thoroughly. This study will be carried out over a sufficiently long period of time and will cover the entire latitudinal structure of Jupiter enhancing the authenticity of the recorded data. 

The JUICE spacecraft moving through Jupiter and its large moons: Ganymede, Europa, Io and Callisto. ​Image credit: ESA/M Carroll

The study of Jupiter's magnetosphere will include a 3D analysis of the magnetodisc and will also study the coupling processes within Jupiter's magnetosphere, ionosphere and thermosphere. JUICE will also study the magnetosphere's interaction with the Galilean moons and its impact on their tidal evolution.

Jupiter Icy Moon Explorer Mission. Video credit: SatTV

Internal oceans – harborers of life?

JUICE will focus on the 3 ocean-bearing worlds, Ganymede, Europa, and Callisto and will specifically focus on Ganymede because of its unique magnetic and plasma interactions with the Jovian magnetosphere.

For Ganymede and Callisto, JUICE will focus on a study of the physical properties of the ice crust, a topographical, geological and compositional study of the surface and finally a description of the ocean layers and detection of any subsurface water bodies.

For Europa – the strongest contender for the presence of extraterrestrial life, JUICE will focus on the presence of the building blocks of life like organic molecules and it will also study the composition of the non-water material on the moon's surface.

Artist's impression of the JUICE spacecraft. Image credit: ESA/ATG Medialab

​The JUICE mission represents a key milestone in the study of the outer solar system and also offers an exciting opportunity to study the presence of water and extraterrestrial life in the 3 largest Jovian moons.

• ESA/JUICE homepage

Featured image credit: Artist's impression of the JUICE spacecraft. Image credit: ESA/ATG Medialab