The European Space Agency (ESA) is embarking on one of its most ambitious missions ever by launching a satellite mission to the planet Jupiter. The Jupiter Icy Moons Explorer (Juice) mission aims to investigate whether the major moons of Jupiter, Callisto, Europa, and Ganymede, could support life. The satellite will take eight years to reach the planet, with a series of flybys of Venus and Earth helping to propel it towards its intended destination. Upon arrival in the Jovian system in July 2031, the mission will perform 35 close passes of the moons, getting as close as 400km to their surfaces.
Juice will not be designed to detect life, nor will it be sending back images of alien fish. Instead, the mission will study the moons’ hidden oceans to determine whether they could support simple microbial organisms. The icy worlds are thought to hold oceans of liquid water at depth, and it is hoped that Juice can establish whether they might also have the conditions needed to sustain life.
Although Mars has been the focus of much research into the possibility of extraterrestrial life, the icy moons of Jupiter and Saturn have also started to pique the interest of astrobiologists. Despite being in the cold outer reaches of the solar system and far from the sun, these worlds could potentially satisfy the four inputs necessary for life: liquid water, nutrients, an energy source, and time. The constant gravitational squeezing and pushing the giant planets exert on the moons provide a means to keep water in liquid form and could drive the kind of volcanic vent systems on ocean floors that could have been the origin of life on Earth.
Juice will carry ten instruments, including cameras, particle detectors, and a radar to map sub-surface features. The mission will also carry a lidar that is used to create 3D maps of surface terrain. However, it is the UK-provided magnetometer that could provide some of the most influential data. The experiment, built by Imperial College London, will provide crucial information on the moons’ hidden oceans, including their depth, salt content, and whether they are in contact with the rocky mantle. At Ganymede, in particular, the information should be quite detailed.
“If we find evidence for life on the moons of Saturn or Jupiter, then almost certainly it would be of independent origin,” says Astronomer Royal, Prof Sir Martin Rees. “That then would carry a momentous message that life – if it had started twice, independently, in our Solar System – can’t be a rare fluke, and almost certainly exists in a billion places in our galaxy, and it completely transforms the way we look at the sky.”
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