Almost 10 years ago the European Space Agency (ESA) selected Jupiter and the largest of its moons, Ganymede, to develop one of its most ambitious missions to explore the solar system. It’s all about the mission JUICE (JUpiter ICy Moons Explorer), which is scheduled to be released on April 13. JUICE will travel to the Jupiter system and its moons exploring icy worlds that have oceans of liquid water hidden under icy crusts of unknown thickness.
trip to the oceans
Liquid water is the fundamental requirement for life, but it is very scarce in the solar system and is rare on terrestrial planets like ours. However, it is abundant in the interior oceans of the moons of Jupiter and Saturn, where they might realize the right conditions for life to develop. Studying the similar miniature solar system that makes up Jupiter and its moons helps to learn about other systems. Indeed, many stars have gas giant planets, and many of these could have similar satellites, with icy materials rich in water.
The orbital diversity of these exoplanets could make many of these moons suitable environments for the emergence of life. So, JUICE will study the Jupiter system as an archetype of a miniature planetary system with worlds rich in water. Their journey will serve to determine the habitability of the subterranean oceans of their moons.
Jupiter, its moons and liquid water
Jupiter is the largest of the planets in the solar system. At 318 times the mass of Earth and orbiting the Sun five times farther, its training dominated the history of the solar system. Jupiter was formed after accumulating huge amounts of hydrogen and helium that closed it into a gas giant without a defined surface. Given its immense gravity, the same processes that led to the formation of planets orbiting the Sun gave rise to the formation of small worlds orbiting Jupiter.
Among these worlds, four satellites comparable in size or larger than our Moon stand out: they are Io, Europa, Ganymede and Callisto, four worlds as different from each other as are the terrestrial planets. These four moons are heated in their interior by the tidal forces generated by Jupiter’s gravity.
Ganymede, Io, Europa and Callisto
Io it is a rocky world covered in sulfur compounds. It has gigantic volcanoes through which the material from massive eruptions escapes into space.
Europe it has a surface that shows countless lines and faults in a geologically young landscape without craters or mountains. In Europa occasional geysers are activated by escaping water vapor from a hot but less active interior than Io. Its icy crust could be as little as 20 kilometers thick.
ganymede, orbiting Jupiter a little further away, is the largest of the moons in the solar system and has large craters in huge areas that melted and solidified in the remote past. in its inland and saline ocean a magnetic field is formed that creates auroras at its equator.
CallistoOrbiting Jupiter nearly two million kilometers away, it is a dark, cratered world covered in water ice, carbon dioxide, and organic compounds.
an extreme planet
in the gigantic Jupiter superlative scale phenomena occur. In its superficial atmosphere we find permanent winds of 500 kilometers per hour that 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 a horizontal size 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 a magnetosphere of 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, producing dark mists of complex organic molecules.
JUICE’s mission on the move
JUICE will arrive on Jupiter in 2032 and during 4 years it made 66 orbits around the planet, progressively approaching the orbit of Ganymede. During that time JUICE will study Jupiter’s atmosphere and magnetosphere, allowing us to understand how such a complex world works.
JUICE will observe the dark rings that surround the planet and examine its smaller moons. These data will provide us with essential details to understand how Jupiter and its moons formed and the impact their formation had on the history of the solar system.
Life can be on 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 entering its 500 km high orbit. There he will explore this world larger than Mercury for 2 more years.
At the end of the mission, and if it has enough fuel, it will descend to a closer orbit, 200 km from the surface. Thanks to its 10 scientific instruments and the exploration of the upper geology of Jupiter’s moons, JUICE will tell us how thick the icy crusts of these worlds are, do they have liquid water and how they are formed, and will give us fundamental information about the molecules organic matter found on their surfaces.
The insights that JUICE will generate, together with the information we have on exoplanets, will give us key information about how abundant icy satellites are in the universe, and what their potential habitability is. Perhaps it is on icy worlds like these, and not terrestrial planets like ours, where elusive life abounds.