Journey to the underground oceans of Ganymede and the moons of Jupiter: what will JUICE discover?

Nearly 10 years ago, the European Space Agency (ESA) selected Jupiter and its largest moon, Ganymede, to develop one of its most ambitious solar system exploration missions. This is the JUICE (Jupiter ICy Moons Explorer) mission, which is scheduled to launch on April 13th. JUICE will travel to the Jupiter system and its moons, exploring icy worlds that have oceans of liquid water hidden under an ice crust of unknown thickness.

Journey to the oceans

Liquid water is a fundamental requirement for life, but it is very rare in the solar system and rare on terrestrial planets like ours. However, there is a lot of it in the inner oceans of the moons of Jupiter and Saturn, where, perhaps, suitable conditions for the development of life may exist. Studying the miniature solar system, made up of Jupiter and its moons, helps to learn about other similar systems. Indeed, many stars have gas giant planets, and many of them may have similar moons with water-rich icy materials.

The orbital diversity of these exoplanets could make many of these moons suitable environments for the emergence of life. Thus, JUICE will study the Jupiter system as an archetype of a miniature planetary system with water-rich worlds. Their journey will serve to determine the habitability of their moons’ subterranean oceans.

Jupiter, its moons and liquid water

Jupiter is the largest of the planets in the solar system. With a mass 318 times that of the Earth and orbiting the Sun five times as far, its formation has dominated the history of the solar system. Jupiter was formed after the accumulation of huge amounts of hydrogen and helium, turning it into a gas giant without a defined surface. Given its enormous gravity, the same processes that led to the formation of planets orbiting the Sun led to the formation of small worlds orbiting Jupiter.

Among these worlds, four satellites stand out, comparable in size or larger than our Moon: these are Io, Europa, Ganymede and Callisto, four worlds as different from each other as the terrestrial planets. These four moons are heated from the inside by tidal forces created by Jupiter’s gravity.

Ganymede, Io, Europa and Callisto

Io is a rocky world covered in sulfur compounds. It has giant volcanoes through which material from massive eruptions escapes into space.

Europa’s surface has countless lines and faults in a geologically young landscape with no craters or mountains. From time to time, geysers are activated on Europa, ejecting water vapor from hot, but less active bowels than on Io. Its ice crust can be only 20 kilometers thick.

Ganymede, orbiting Jupiter a little further, is the largest of the moons in the solar system and has large craters and a vast area that melted and solidified in the distant past. In its bowels and the salty ocean, a magnetic field is formed, creating auroras at its equator.

Orbiting Jupiter nearly two million kilometers away, Callisto is a dark, cratered world covered in water ice, carbon dioxide and organic compounds.

extreme planet

Phenomena of superlative scale occur on giant Jupiter. In its surface atmosphere, we find constant winds of 500 kilometers per hour, which carry clouds of ammonia that completely cover the planet. In the clouds, we see extreme convective storms that can last for weeks and grow to horizontal dimensions larger than the Moon, and whose roots are in water clouds 100 km deep.

In many places on the planet, inside and outside of storms, we see lightning that can be a thousand times more energetic than terrestrial lightning.

Jupiter’s magnetic field extends through the magnetosphere for hundreds of millions of kilometers, forming the largest structure in the entire solar system. This intense magnetic field generates permanent auroras that warm the polar atmosphere, creating dark fogs of complex organic molecules.

Mission JUICE is on the way

JUICE will arrive at Jupiter in 2032 and in 4 years will make 66 revolutions around the planet, gradually approaching the orbit of Ganymede. During this time, JUICE will study the atmosphere and magnetosphere of Jupiter, which will allow us to understand how such a complex world works.

JUICE will observe the dark rings surrounding the planet and explore its smaller moons. This data will provide us with important details to understand how Jupiter and its moons formed and what impact their formation had on the history of the solar system.

Life can be in frozen worlds

During the initial exploration of the Jupiter system, JUICE will fly over Europa twice, make 21 close flybys of Callisto and more than 20 flybys of Ganymede before reaching its 500 km altitude orbit. There he will explore this world larger than Mercury for another 2 years.

At the end of the mission, if it has enough fuel, it will descend to a closer orbit, 200 km from the surface. Through its 10 scientific instruments and its study of the upper geology of Jupiter’s moons, JUICE will tell us how thick the ice crusts of these worlds are, how much liquid water they contain and how they formed, as well as give us fundamental information about the organic molecules on their surface.

The knowledge that JUICE will generate, together with the information we have about exoplanets, will give us key information about how numerous icy satellites are in the universe and what their potential habitability is. Perhaps it is on such icy worlds, and not on terrestrial planets like ours, where elusive life abounds.

Ricardo Hueso Alonso, professor of physics at the University of the Basque Country. His research is focused on the study of planetary atmospheres, University of the Basque Country / Euskal Herriko Unibertsitatea.

This article was originally published on The Conversation. Read the original.

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