He is the giant among our planets. Moons orbiting it are themselves the size of planets. And it is now the target of the European Space Agency Esa's farthest-reaching mission to date: the gas giant Jupiter and its satellites. Hundreds of millions of kilometers away, the question is whether there could be life on Jupiter's moons.
The launch of the "Juice" (Jupiter icy moons Explorer) probe from the Kourou spaceport in French Guiana is scheduled for April 13th. With her ten instruments on board, she should then primarily take a look at the large moons, because there is water under a kilometer-thick ice shell. "Three moons have oceans, and they actually have a lot of water," says mission engineer Angela Dietz from the ESA control center in Darmstadt. This is where the mission, which will cost more than a billion euros, will be controlled in the coming years.
"Europa", "Kallisto" and "Ganymede" are the moons that the scientists want to look at from 2031 after the probe's journey of many years. For all three moons, the researchers assume that there are seas under ice. The conditions for life could be fulfilled there. Scientists assume that you need water, you need energy, you need stability over several million years, as Dietz explains. ""Europa" already has the greatest probability because it is closer to Jupiter, which has more heat and energy." So, theoretically, there could be life in the ocean there. "We can only examine whether the basics are there," says Dietz. A direct detection of living beings is not possible.
Is there life on Jupiter's moons?
Certain elements that can serve as building blocks for molecules are needed for the emergence of life. "There are chances on "Europa" and "Ganymed", says Dietz. With the ten instruments, nine from European partners and one from the US space agency Nasa, various investigations are possible, including radar and laser measurements. The radar can also collect data under the ice layer. According to Dietz, you can go up to 19 kilometers through the ice. No such radar was on board on previous NASA missions to Jupiter.
The Institute for Planetary Research at the German Aerospace Center (DLR) in Berlin was also on board with the instruments. The "Gala" laser altimeter (Ganymede Laser Altimeter) is to be used to measure the surface of "Ganymede", says Hauke Hussmann, who is responsible for the "Gala" experiment. "We scan virtually the entire "Ganymed"". This is important in order to understand the development of the moon. "The second important aspect to be added to the Jovian system is tidal deformation." The moons would deform as they orbited the planet.
"The extent of this change over time can tell us whether there is liquid water inside, i.e. whether there is a global ocean on 'Ganymed', as model calculations predict," says Hussmann. With the data and images from the "Janus" camera, in which DLR played a major role, a digital 3D model of the moon, which is completely covered with ice, can later be created.
How can it be that water exists there?
But how is it possible that liquid water should exist hundreds of millions of kilometers away from the sun? "Jupiter, with its enormous mass, has huge tidal forces that it exerts," says Hussmann. This leads to friction inside the moons and heat is generated as a result. "This is the energy source that plays a significant role in the moons."
Before the probe can start its work on Jupiter, it still has a long journey ahead of it. After launch, it will unfold its solar panels measuring 85 square meters. Before heading out to the outer solar system, however, it will fly once more around Venus and three times around Earth on its eight-year journey to gain speed.
Probe scheduled to arrive at Jupiter in 2031
According to Dietz, the journey through the asteroid belt between Mars and Jupiter is no problem for the flight. According to the plan, the six-ton probe should arrive at Jupiter in 2031. There "Juice" will fly past the moons. The probe will only fly past "Europa" twice. "The moon is close to Jupiter. Jupiter has a very high level of radiation and gravitational forces are also very strong there," says Dietz. That is also a question of safety for "Juice".
Finally, the probe will enter an orbit around Ganymede, the largest of the moons and the only satellite with a magnetic field in the solar system. The probe is expected to crash there in September 2035.