If there is life beyond Earth, it could be lurking in the deepest oceans of a moon of Jupiter, keeping its secret from humans since the dawn of time.
But Ganymede, Europa and Callisto are not the hiding places they once were, with a spacecraft about to be launched that could get us closer to what European scientist Nicolas Altobelli calls “the smoking gun”.
“It’s like a big ship that we send to discover America,” said Mr Altobelli, the mission manager of the Jupiter Icy Moons Explorer, or Juice, which launches in April.
Engineers are taking no chances. When The National saw Juice up close at an Airbus factory in France, nobody could even look at the spacecraft without changing into shower caps and surgical gowns and handing in their smartphones.
The uncrewed orbiter is about the size of a garden shed, has gadgets strapped to its hull and is expected to reach Jupiter in 2031. It will carry vast solar panels to soak up what little energy it can, 800 million kilometres away, where the Sun could barely power a hairdryer.
Scientists in Toulouse, the hub of European aerospace from where Concorde first took off in 1969, will feel the weight of history when they let their “baby” go to the launch pad.
Project manager Giuseppe Sarri likes to leaf through Galileo Galilei’s diaries from 1610, when he discovered Jupiter’s biggest moons, and imagine what the father of modern astronomy was doing on a January day back then.
An engraving of Galileo’s work was mounted on the spacecraft last week, in tribute to the giant upon whose shoulders Juice is standing. (A joke at Airbus: let’s hope any aliens who find it can read Latin).
The mission is a big test for the European Space Agency, its first tour to the outer solar system without Nasa taking the lead. It comes amid a wider push to make Europe less reliant on the US in defence and technology.
Two European space launches have recently gone wrong, including Britain’s Virgin Orbit mission, but those on the Jupiter project are adamant they have a superior rocket in the experienced Ariane 5.
Still, Mr Sarri admits to having some butterflies in his stomach as the April launch window approaches.
“When you launch, there is always a little bit of tension. But we are not concerned with a new launcher, or an almost new launcher or a launcher that just had a problem,” he told The National.
Life on the moons?
The case for life on the moons goes like this. Ganymede, Europa and Callisto are thought to have hidden oceans beneath their surfaces. We know that life can exist without sunlight deep in the Earth’s oceans. Indeed, it might have started there. Ganymede is virtually planet-sized and has an unusual magnetic field, a bit like Earth’s, that shields it from radiation. All this means that Jupiter’s worlds might be a bit like ours.
Juice’s instruments could pick up clues — an organic molecule here, a surprising atom there — that show the moons are habitable.
That would be enough to delight Mr Altobelli’s team, even if it leaves the ultimate question unanswered.
“We are now doing oceanography in the outer solar system, we are doing astrobiology,” Mr Altobelli said.
“Potentially you have conditions favourable for life. That would be really exciting.”
The Galileo plaque was one of the final finishing touches before Juice is transferred to French Guiana for launch.
A launch has to be timed with the orbit of the planets and the ideal date would be April 14, when the stars would so align that Juice would save fuel and have more in the tank for Jupiter.
It means the weather this spring could determine how close Juice gets to Ganymede many years down the line, said Mr Altobelli, who hopes it might fly within 200km of the surface.
Before then, Juice will take an eight-year cruise through the solar system, passing by Venus and Earth to pick up momentum and slingshot itself towards Jupiter.
That means it will have to withstand the 250ºC heat of Venus and the minus 230ºC cold of Jupiter, adding to the challenges of the long distance and harsh radiation.
The craft will be in virtual hibernation while en route but become a powerful computer once it reaches Jupiter, said Justin Byrne, the head of science at Airbus’s defence and space division.
Juice’s 2.4-metre antenna will beam so much data back to Earth that it will take months to download everything, which could include stunning new images of the moons.
“The spacecraft is designed to take care of itself. It’s fully autonomous. If there are any failures it reconfigures itself into a safe mode,” Mr Byrne said.
“When it gets to Jupiter, it’s really full-on. It is moon fly-bys every few days, the amount of operational data is really unique”.
Once it reaches Ganymede in 2034, Juice will attempt a first: entering the orbit of a moon that is not our own.
“Knowing what is below the moon is important,” Mr Sarri said.
“Are these oceans like ours, or are there maybe 100km of water? We cannot see because it’s too deep. If we see that there are profiles, structures, difference of temperatures, maybe current, that make these oceans like ours, then we can hope that maybe this is a potential place of life.”
Ganymede’s greatest secret could remain tantalisingly out of reach, but Juice should get closer than ever before, literally as well as figuratively. At the end of its life, expected in 2035, it will run out of fuel and crash into the moon’s icy surface, sitting above the oceans in its final resting place.