‘It’s like finding needles in a haystack’: the mission to discover if Jupiter’s moons support life
For most of the past 200 years, were you to ask an astronomer where the most likely place in the solar system is to find life, the answer will have been Mars. The red planet and its potential inhabitants have captured our collective imagination for centuries, transforming from an imaginary canal-building civilisation in the 19th century to the much more scientifically plausible microbes of today. But now, the thinking is different.
In the past few decades, astronomers have been increasingly drawn to the deeper, darker realms of the solar system. Specifically, they have become fascinated by the icy moons of Jupiter and Saturn. Years of research have all but proved that some of these moons contain vast oceans of liquid water below their frozen surfaces.
On Earth, water is the number one prerequisite for supporting life. So could these icy moons be habitable too?
In April, the European Space Agency (Esa) will launch a mission designed to find out.
The Jupiter Icy Moons Explorer (Juice) is now at Esa’s spaceport in Kourou, French Guiana. It is undergoing final testing and fitting to its launch vehicle, an Ariane 5 rocket similar to the one that propelled the James Webb space telescope into orbit in December 2021.
Yet even to those in the field of astrobiology there is a sense of incredulity about the idea of investigating planetary habitability on Jupiter’s moons.
“If you said to someone 50 years ago, I’m gonna go and look for life in the outer solar system around the gas giant planets, people would have thought you were mad because there was no reason to think that it was a reasonable proposition at all,” says Charles Cockell, one of the directors of the UK Centre for Astrobiology at Edinburgh University.
What changed was a set of measurements from a Nasa mission in the 1990s that, at first, made no sense.
Every time the Galileo spacecraft drew near to Europa, one of Jupiter’s icy moons, readings from the magnetometer instrument indicated that something inside the moon was interfering with the mighty magnetic field generated by Jupiter.
To collect more of these strange readings, Margaret Kivelson, the instrument’s principal investigator, and