Mission to Jupiter will investigate whether its moons are habitable – 09/04/2023 – Science

The ESA (European Space Agency) is about to launch its first unmanned mission to Jupiter – and it will be the most daring ever dispatched to study the largest planet in the Solar System.

Juice, an acronym for Jupiter Icy Moons Explorer, or Explorer of the Icy Moons of Jupiter, resembles large NASA missions, made up of very expensive spacecraft transporting a complete set of instruments to make all kinds of observations. All this at a cost of 1.5 billion euros.

The European probe has already been encapsulated and placed on top of the Ariane 5 rocket, which should take it into space, barring technical or meteorological unforeseen circumstances, next Thursday (13). The launch will take place from the ESA-operated Kourou center in French Guiana.

It is the beginning of a long journey, which will involve using the gravity of the Moon, Earth and Venus to slingshot it to Jupiter (learn more below), arriving there only in July 2031, when it will become the first mission not America exploring the largest planet in the Solar System.

Its main objectives are to make a complete characterization of the gas giant and a detailed study of 3 of its 4 largest moons: Europa, Ganymede and Callisto. There are strong indications that at least the first two, but possibly all three, are ocean moons, that is, they have saltwater oceans beneath their frozen crusts.

“The main goal is to understand whether there are habitable environments on these icy moons and around a planet like Jupiter,” explained Olivier Witasse, the mission’s project scientist, at a press conference last Thursday (6). “We are going to characterize these oceans, determine where they are located, how deep they are, what the composition of that water is. And, to understand this question of habitability, we have to study the Jupiter system globally.”

With an impressive set of sensors, Juice will try to characterize these oceans and maybe even find possible biochemical signatures that there may be life thriving there (although this is not a declared objective of the initiative).

Notably, the most hyped of the three moons for prospecting for life, Europa, is the one that will get the least attention from the mission: of the 35 flybys planned for the first four years of the mission, only 2 will be aimed at Europa. Most of them (21) will be on Callisto, and the remaining 12 will be on Ganymede, the largest moon in the Solar System. At 5,268 km in diameter, it is larger than the planet Mercury and the only one to have its own magnetic field, one of many items that Juice will study in detail.

The apparent contempt for Europa does not come without reason: NASA (the American space agency) is also working on a new orbiter for Jupiter, called Europa Clipper, which will have as its main objective to carry out repeated flybys of this Jovian moon. It will launch next year and should reach Jupiter in 2030, a year before Juice itself.

In addition, the radiation environment on Europa is much more aggressive than on the two outermost moons, Ganymede and Callisto, which can lead to spacecraft degradation if it is not adequately shielded.

With some coordination between the American and European missions (which curiously were born from the proposal of a single gigantic international mission), it is possible to maximize the knowledge gathered by the two projects. The groups hold joint annual meetings and are in constant contact, even before their respective spacecraft launches.

If the American Europa Clipper will focus, as the name suggests, on Europa, the big star of the European Juice (besides the planet Jupiter, of course) will be the moon Ganymede. In late 2034, the probe will do something no other probe has ever done and orbit a Solar System moon other than our own, spending at least another ten months (and potentially much more time) studying it up close.

SIMILAR BUT DIFFERENT

The three Jovian icy moons each have a personality. Europa is the most active and stormy, with clear signs of constant renewal of its ice crust, displacement of plates and possibly the emission of water plumes from the subsurface ocean, through fissures. It is estimated that Europa’s ocean is in direct contact with a rocky core, making this environment very similar to the one that probably gave rise to life on Earth.

Ganymede, meanwhile, has both young and old land on its frozen surface, and there are clear signs that a saltwater ocean also exists beneath the ice crust. But models of the moon’s internal structure suggest that the watery layer is sandwiched between two layers of ice, one above and one below, preventing direct contact between the ocean and the rocky core. This makes it a less promising target for the search for life, but it cannot be ruled out entirely.

Finally, Callisto represents a testimony of what the Jupiter system was like at the beginning of the history of the Solar System. With a dark, ancient and heavily cratered surface, it may also have a subsurface ocean, but that’s something Juice will certainly help confirm or disprove.

A BIG SPACESHIP

To do all this, the European probe built by the company Airbus was equipped with the largest solar panels ever launched on an interplanetary mission. There are a total of 85 square meters of photovoltaic panels, carefully folded for launch, waiting for the command to open in space.

The need for the large panels is to provide adequate electricity for the spacecraft even as it orbits Jupiter, about five times farther from the Sun than Earth. The level of solar radiation is 25 times more intense here than there, but Juice will still have around 850 watts to power its instruments.

There are ten of them, in addition to an experiment involving the communication antenna for the precise determination of the position and speed of the probe and a radiation meter. With the set, the probe will produce complete data of the space environment in the Jovian system, as well as remote sensing of the turbulent clouds of the planet and mapping the surface of the moons visited.

Witasse sees the mission as an effort that goes beyond understanding the history of Jupiter and its satellites. “Jupiter is a miniature solar system, so understanding it helps us understand the formation of our own solar system, how it evolved over time, and it will also help us understand other extrasolar systems.”

To date, only two missions have orbited Jupiter, the American Galileo (which arrived there in 1995 and operated until 2003) and Juno (still in operation, arriving in the Jovian system in 2016). In a few more days, another journey to the giant begins.