Could the mysterious moons of Jupiter be hiding habitable zones under their icy crusts?
The Rosetta mission’s startling discovery that Comet 67P contains multiple organic compounds that make up the building blocks of life adds weight to a theory that Earth may have been seeded with those vital ingredients.
So could life exist elsewhere outside our own planet and indeed beyond our solar system?
Attention is now focusing on the Jovian system.
NASA has included $30 million in its 2016 budget to plan a mission to Europa — one of the moons of Jupiter — because there is some evidence of the presence of water. In 2012 the Hubble Space Telescope observed water vapor above the south polar region of Europa.
And work begins this summer on a spacecraft that will explore the gas giant Jupiter and several of its moons after Airbus Defence and Space in France was selected by the European Space Agency (ESA) to build the probe for a launch in 2022.
Called Juice, (from JUpiter ICy Moons Explorer) the mission aims to study not only Jupiter and Europa but two of its other moons — Ganymede, and Callisto.
It will spend 3.5 years exploring the Jovian system after a journey taking more than seven years.
Project scientist for the Juice mission, Olivier Witasse, told CNN that there was no direct proof, but hints that there could be oceans hidden below the moons’ crusts.
“The mission aims to try to confirm this and find out how deep they are,” he said.
Witasse said the project, which will cost about 900 million euros (about $993 million), is very exciting because it will allow for “multiple flybys of diverse moons.”
To date, most of the planets discovered beyond our own solar system — so-called exoplanets — have been gas giants. If Juice could find evidence of habitable zones on the moons of Jupiter then it gives hope to those looking for habitable environments in the wider universe.
ESA says on its Juice website: “Understanding the Jovian system and unravelling its history, from its origin to the possible emergence of habitable environments, will give us a better insight into how gas giant planets and their satellites form and evolve. In addition, new light should be shed on the potential for the emergence of life in Jupiter-like exoplanetary systems.”
It’s a possibility that fascinates Joanna Barstow, a researcher in planetary science at the University of Oxford.
“Since long before we started our robotic exploration of the solar system, we wondered if there was life on another world,” she said.
“Some of the moons of Jupiter, even though their surfaces are covered with ice, might have liquid water oceans hiding under the surface. Maybe they are sheltering bacterial life as well? We’d love to find out.
“Finding rocky planets around other stars is tricky, because they are so small — the Earth is less than a tenth the size of Jupiter. So finding Jupiter-sized planets is much easier, and there’s no reason why we wouldn’t expect other Jupiters to have moons. But a cautionary word — we have never found an exo-moon, and of course they are also small, and small things are hard to see.”
The Juice mission faces considerable challenges.
Didier Morancais, key account manager for science and exploration at Airbus Defence and Space, explained that the solar panels have to be huge to be able to generate enough power at Jupiter where he said the sunlight energy is 25 times lower than on Earth. The company says solar generators will cover 97 square metres — the largest ever built for an interplanetary mission.
The panels also have to be light but strong enough to withstand the forces of deceleration when the probe is put into orbit.
Juice will tour the three moons, spending eight months orbiting Ganymede. It requires a complex trajectory that Morancais described as “highly critical.”
If that wasn’t difficult enough, the instruments have to be shielded from the intense magnetic field around Jupiter which can interfere with the sensitive equipment.
So what does NASA say about the target moons on its website?
Europa: The moon stretches and flexes in its orbit, creating heat and possibly explaining the cracks seen on its surface. It is thought that there could be a saltwater ocean beneath a thin ice shell.
Callisto: NASA says it is the most heavily cratered object in the solar system. Its interior is a rocky core surrounded by a large ice mantle.
Ganymede: Although a moon, it is larger than both Mercury and Pluto and has an iron core surrounded by a shell of ice and rock.
Any discoveries from Juice are more than 15 years away but in the meantime, the search for more Earth-like planets goes on.
Barstow points to one particularly interesting discovery that is tantalizing scientists.
“Gliese 1214 b is a type of planet we call a Super-Earth — a bit bigger than Earth, a bit smaller than Neptune. It’s not dense enough to be rocky so it’s probably like a warm mini-Neptune. There’s nothing like it in our solar system and we don’t really know what to expect,” she said.
“On my wish list for the future is a telescope to study exoplanets like Gliese 1214 b in more detail. I want to know what’s going on beneath that cloud layer!”
