moon landing

JUICE: The spacecraft could change our understanding of life in the universe

Jupiter's moons are some of the most intriguing places in the solar system. JUICE will provide a closer look.

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Jupiter’s moons fascinate astronomers for several key reasons, but chief among them is the idea that some could host life.

To find answers to this and some of astronomers' most pressing questions, the European Space Agency plans to launch a new probe to study Jupiter and its many moons, aka JUICE, or JUpiter ICy moons Explorer.

Beyond a truly incredible acronym, what does JUICE hope to accomplish? Let’s delve into the science.

An artist's depiction of JUICE.


What is JUICE?

The JUICE spacecraft will travel from Earth to Jupiter equipped with ten scientific tools to study Jupiter’s moons, as well as the planet itself. The craft is an international effort, with the ESA getting help from America’s NASA and Japan’s Aerospace Exploration Agency (JAXA) to develop the spacecraft’s ten scientific instruments.

But the core hardware for the project is being built by ESA contractor Airbus Defence and Space, based out of Germany.

The four Galilean moons

Stocktrek Images/Stocktrek Images/Getty Images

Will JUICE study all of Jupiter’s moons?

No. Jupiter has 79 (or more) moons, some of which have been discovered quite recently. But JUICE will focus on three major ones, known as the Galilean moons. Together, Ganymede, Callisto, and Europa were named for their discoverer, none other than Galileo Galilei in the early 1600s (there’s also a fourth Galilean moon, Io).

JUICE’s acronym hints at what these three moons have that makes them worthy of study: icy surfaces that could be hiding vast depths below. There are tantalizing hints of “irregular lumps” underneath Ganymede’s surface, an ocean interacting with rock could exist on Callisto, and NASA notes that Europa is widely considered “the most promising place to look for life beyond Earth.”

Europa's surface, which features a wide-ranging network of cracks, ridges, and bands.

NASA/JPL-Caltech/University of Arizona

Ganymede, seen from the Galileo spacecraft in 1995.


Callisto, as seen from the Galileo spacecraft. The moon's deep surface scars suggest a long history of impacts.


Each of these moons offers its own mystery to scientists.

How will JUICE study them?

JUICE will use a variety of instruments to probe these moons' icy depths. These tools will be products of international collaboration, with contributions from France, Italy, Germany, Japan, America, Sweden, and others.

Here are four of the tools JUICE will have at its disposal:

  • Moons And Jupiter Imaging Spectrometer, or MAJIS, will study clouds in Jupiter’s troposphere, the highest element of Jupiter’s atmosphere, as well as minerals on the surface of the three moons.
  • Gravity & Geophysics of Jupiter and Galilean Moons tool, also known as 3GM promises to “revolutionize our understanding of the origin, evolution and structure” of Ganymede by using microwave frequencies to determine the nature and extent of any ocean that exists below the moon’s surface.

NASA's contribution to RIME, a transmitter.

  • Radar for Icy Moon Exploration, or RIME will be able to send out radio waves capable of going through seven miles of ice and water to detect whatever lies below. For Europa, which has an icy shell between 10 to 15 miles deep, RIME will examine the nature of that shell. For Ganymede and Callisto, it could be exploring oceans.
  • GAnymede Laser Altimeter, or GALA. Laser altimeters are used to study the topography of planets, NASA also uses one to study the Moon. By specifically focusing on Ganymede, scientists hope to understand a moon-wide crater that could be the largest impact structure in the Solar System.

What’s the timeline?

The ESA hopes to launch JUICE by 2022. After that, it’s a long voyage to Jupiter. The ESA estimates it will take JUICE 7.6 years to get to reach the Jovian system, so an ETA 2029 at the earliest.

Once the craft makes it there, it will start on a three and a half year mission between its four sites.

Will JUICE be alone?

Not all of the time. NASA is also planning a mission to study the Galilean moons, the Europa Clipper, to compliment JUICE.

Although the Clipper is launching in 2024, NASA hopes that its Space Launch System will be able to make up some of the time difference and have the two craft studying the moons for around the same time period.

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