So far, we can only be sure that life exists in one place across the entire universe – Earth. In the past, the planets either side of ours have been considered good candidates for new discoveries, but it seems unlikely: Venus has a toxic atmosphere and surface temperatures of around 475 degrees celsius, while Mars lost its atmosphere and dried up billions of years ago. That isn’t going to stop us looking, though, and a new, £1.4 billion mission is set to take the search further into the solar system, to the icy moons of the gas giant Jupiter.

Dubbed Juice, AKA the Jupiter Icy Moons Explorer, the probe is scheduled to be blasted into space today (April 13) at 8:15 am ET, on board an Ariane 5 launcher (the same rocket that proved a huge success for the James Webb Space Telescope in 2021). Unlike the JWST, which took around a month to reach its final destination, Juice will travel for around eight years to reach Jupiter, slingshotting around Earth and Venus to maintain its speed.

The main target? Ganymede, the largest moon in Jupiter’s orbit (and the rest of the solar system) at about one and a half times the size of our own moon. After flying by a couple more of Jupiter’s moons, Callisto and Europa, Juice is set to settle into an orbit around Ganymede in 2034, marking the first time a spacecraft has established a permanent orbit around a non-Earth moon.

That’s not the only groundbreaking part of the Juice mission, though. There’s strong evidence that, underneath their icy surfaces, Ganymede, Europa, and Callisto have salty oceans that might even hold more water than Earth’s surface. This is significant because liquid water is a prerequisite for life on Earth – if Jupiter’s moons have it too, that boosts the chances of finding some sort of alien life. Back in 2005, it was also discovered that Enceladus, a tiny moon orbiting Saturn, has an underground ocean that’s spewing water and organic material out into space.

Obviously, it will be a while until we get any kind of confirmation of alien life from Juice, which will be launched from the European Space Agency’s spaceport in Kourou, French Guiana. During its journey, in fact, it will be overtaken by a separate NASA probe, the Europa Clipper, taking a slightly shorter route to investigate... you guessed it, Europa, by April 2030.

Unfortunately, the Europa Clipper’s investigation is predicted to be limited to just three and a half years, due to radiation complications. Juice, on the other hand, is thought to be able to survive in Ganymede’s orbit. 

Any discoveries of extraterrestrial life from either probe would be revolutionary. Not only would it settle the debate about our exceptional existence on Earth once and for all, proof that life can evolve elsewhere would also open up the likelihood of life flourishing in the wider universe.

The launch of Juice is streamed by ESA below.