Image Credit: NASA

Jupiter, its magnetic environment and its moons form one of the most intriguing systems in the Solar System. Scheduled to launch in 2023 and reach Jupiter in 2031, ESA’s Juice Jupiter Icy Moon Explorer will reveal more about this fascinating planet and its natural satellites.

The mission will primarily investigate five areas, from Jupiter’s turbulent atmosphere to the putative liquid oceans on three of its planet-sized moons: Ganymede, Europa and Callisto.

What are the ocean worlds of Jupiter like?

Jupiter’s four largest moons are known as the “Galilee moons”; of these, three are believed to have liquid water oceans hidden beneath their icy crusts (Ganymede, Europa, and Callisto, except for Io, which is not known to be a water world). How far below the surface do these oceans begin, and how deep are they? Do they contain fresh or salt water? If so, how much of each?

Why is Ganymede so special?

Of the three moons, Juice’s main science target will be Ganymede, the largest moon in the Solar System (larger than Pluto and Mercury) and the only one to have an intrinsic magnetic field. Only two other solid bodies in the Solar System generate dipole fields like Ganymede, and both are planets (Mercury and Earth), one of which harbors life.

Ganymede offers an ideal natural laboratory to study the nature and properties of the icy worlds. Juice will become the first orbiter of this ocean world and will use its suite of ten sophisticated instruments to measure how Ganymede spins, its gravity, its interior shape and structure, its magnetic field, its composition, and to penetrate its icy crust using radar up to a depth of about nine kilometers.

Juice will also investigate water vapor and other substances in Ganymede’s atmosphere to fully understand the processes taking place in the space environment of the moon.

Could there be, or ever have been, life in the Jupiter system?

Determining whether the Jovian moons provide the right conditions for habitability is one of Juice’s main goals. Could life have appeared somewhere there? Do any of the Galilean moons have the building blocks necessary for life?

Studying these worlds in depth, Juice will investigate whether the conditions necessary for life could have once arisen on Ganymede, Europa, or Callisto.

It will also help to understand these moons not only as planetary bodies but also as possible habitats for life. Juice’s high-resolution mapping will search for biologically essential and important elements (such as carbon, oxygen, nitrogen, magnesium, and iron).

Knowing its habitability will have far-reaching scientific implications, far beyond the Jupiter system itself, and will help understand the general habitability of icy worlds throughout the Universe.

How has Jupiter’s complex environment shaped its moons, and vice versa?

Jupiter has a powerful and unique gravity, magnetic, and plasma environment. In particular, Jupiter’s magnetic field is about 20 times stronger than Earth’s; Understanding the complex magnetic environment of the planet remains one of the most outstanding mysteries of the Solar System, and Juice aims to solve it. Mainly: how has this harsh environment shaped the conditions of the Galilean moons and how do Jupiter and its moons interact?

Jupiter’s large moons orbit within this intense magnetic and radiation environment, leading to unique interactions between the moons and their environment.

Beyond that, Juice will also investigate Jupiter’s complex gravitational environment; how the moons interact with the tides with each other and with their parent planet.

What does a typical gas giant planet look like? How was it formed and how does it work?

The Jupiter system is an archetype not only for the gas giants of the Solar System, but also for the many giant planets now known to orbit stars other than our own.

One of Juice’s main goals is to understand how gas giant planets and their moons form and evolve.

For example, what processes drive Jupiter’s weather, chemistry, and climate, and how does this change over time on a typical giant planet? From its orbital vantage point, Juice will explore Jupiter’s ever-changing atmosphere on various timescales to reveal the processes that create and shape it.