The search for alien life extends to Jupiter’s icy moons

Could the vast, long-hidden oceans teem with alien life in our solar system?

A new chapter in humanity’s search for extraterrestrial life begins Thursday with the launch of the European spacecraft JUICE on a mission to investigate the icy moons of Jupiter.

First discovered by Italian astronomer Galileo Galilei more than 400 years ago, these ice-covered moons are so far from the Sun that they were long ruled out as potential candidates to host life in our backyard.

Until recently, it was believed that the habitable zone of the solar system “ends at Mars,” French astrophysicist Athena Costinis, one of the science leaders of the European Space Agency (ESA) mission, told AFP.

But NASA’s Galileo probe to Jupiter in 1995 and the more recent Cassini spacecraft’s trip to Saturn caused scientists to broaden their horizons.

The gas giants themselves have been properly ruled out, but their icy moons — notably Jupiter’s Europa and Ganymede, and Enceladus and Saturn’s Titan — have given new hope for life nearby.

Beneath their icy surfaces are believed to hold huge oceans of liquid water – a crucial ingredient for life as we know it.

It will be “the first time we’ve explored habitats beyond the frost line” between Mars and Jupiter, said Nicholas Altobelli, JUICE project scientist at the European Space Agency.

Beyond that line, temperatures drop sharply and “liquid water can no longer exist on the surface,” Altobelli told AFP earlier this year.

“giant” ocean

The Jupiter Icy Moons Explorer (JUICE) mission lifts off from European Spaceport in Kourou, French Guiana, on Thursday for an eight-year journey through space.

By July of 2031, it will have entered Jupiter’s orbit, from which it will explore Ganymede, Europa, and fellow icy moon Callisto.

Then, in 2034, JUICE will enter the orbit of Ganymede, the first time a spacecraft has done so around a moon other than our own.

In addition to being the largest moon in the solar system, Ganymede is also the only one that has its own magnetic field, which protects it from dangerous radiation.

This is just one of several signs that Ganymede’s hidden ocean could provide a stable environment for life.

Unlike similar missions to Mars, which focus on finding signs of ancient life long since extinct, scientists hope that Jupiter’s icy moons will still be home to organisms, even if only small or single-celled.

This habitability requires a power source. Lacking energy from the sun, the moons can instead take advantage of the gravity that Jupiter exerts on its moons.

The force creates a process called tidal heating, which warms the interior of the moons and keeps the water liquid.

Ganymede’s “giant” liquid ocean is trapped between two dense layers of ice tens of kilometers below the surface, said Carole Lariguderie, JUICE project leader at the French space agency CNES.

“On Earth, we still find life forms at the bottom of the abyss,” she added.

Tiny microbes like bacteria and archaea have been found to be able to survive on Earth without sunlight, raising hopes that life elsewhere will be able to do the same.

In addition to water and energy, life needs nutrients.

“The big question, then, is whether Ganymede’s ocean contains” the necessary chemical elements, Kostinis said.

She added that the ocean should be able to absorb nutrients from anything that falls on the moon’s surface, for example, which will eventually dissolve into the water.

Not alone

The JUICE instrument suite will sound the vicinity of Ganymede to determine its depth, its distance from the surface, and, hopefully, its composition.

The European Space Agency’s €1.6 billion ($1.7 billion) probe will spend eight months orbiting Ganymede, coming as close as 200 kilometers (125 miles) to the moon, all shielded from radiation.

It wouldn’t be the only spacecraft lurking around Jupiter.

NASA’s Europa Clipper mission is scheduled to launch in October next year. It will take a faster route to Jupiter, reaching Europa in 2030.

If one — or more — of Jupiter’s moons ticks all the boxes for hosting life, Cyril Cavill, JUICE project manager at Airbus, said the “logical next step” would be to send a mission to land on the surface.

Although there are no plans for such a mission, which could definitively prove the existence of life beyond Earth, “this is part of the dream,” he said.

© 2023 AFP