The giant next door: What clues does Jupiter hold to the future of the solar system?

Elsewhere, gas giants occupy central positions; often, by pushing engulfing smaller planets. Is this where our solar system is headed? Or how it was formed?

Jupiter is the oldest, most influential (being by far the biggest), and arguably the most intriguing planet in the neighbourhood.

A close-up of Jupiter’s south pole taken by NASA’s Juno Probe in 2016. It is a composite of multiple images taken by the JunoCam on three separate orbits, combined to show the entire area in daylight. Each swirl is an Earth-sized cyclone; they are so densely clustered that some are colliding at the edges. (NASA, ESA, CSA, Jupiter ERS Team; image processing by Ricardo Hueso (UPV/EHU), Judy Schmidt)

It was the first to form, three million years after the birth of the solar system. (Saturn came next, within the first 10 million years; as did the ice giants Uranus and Neptune). Jupiter is a gas giant, with no known solid land. Beneath its giant storms is a sea of liquid metallic hydrogen, and a dense metal core.

It is so large that it maintains a massive orbital system of its own, with over 90 known moons, including the four planet-sized ones: Io, Europa, Ganymede and Callisto.

It draws in comets and asteroids, giving it the nickname “vacuum cleaner of the solar system”. But this can make it a tricky neighbour. While it draws space objects away from Earth, it can also fling things our way.

A rather whimsical view of the gas giant Jupiter, taken by NASA’s James Webb Space Telescope. This composite image represents the planet as seen through two filters. In a rare bonus, its faint rings are visible, as are two tiny moons – Amalthea and Adrastea. (NASA, ESA, CSA, Jupiter ERS Team; image processing by Ricardo Hueso (UPV/EHU) and Judy Schmidt)

In 2021, two scientists at Harvard University presented a new theory about how the Chicxulub impactor ended up here. The paper (by astronomer Avi Loeb and astrophysics student Amir Siraj, published in the journal Nature) states that the massive asteroid / comet got caught in Jupiter’s gravitational field, and hurled towards Earth.

It landed, of course, in what is now Mexico; leaving a crater 93 miles across and 12 miles deep; sparking a wave of devastation that rolled across the planet, altered the climate, and began the mass extinction that wiped out the dinosaurs 66 million years ago.

But there are other reasons Jupiter matters. Astrophysicists believe it played a key role in shaping the solar system as we know it. Over and over, in other solar systems, gas giants such as this one occupy central positions. They are often found to have migrated to these positions by pushing smaller terrestrial planets aside, or engulfing them. Is this where the solar system is headed? Or how it was formed?

“We can’t understand the origin of the solar system – and how Earth came about – without understanding how Jupiter formed,” says the why-we’re-exploring-Jupiter statement on the website of the US National Aeronautics and Space Administration (NASA).

This close-up of a swirling vortex on Jupiter was captured by Juno in 2018, from just 7,000 km from the gas giant’s cloud tops, on its 16th close fly-by. (NASA / JPL-Caltech / SwRI / MSSS / Gerald Eichstädt / Sean Doran)

And, as our search for sentient life continues, the focus is on the moons Ganymede (which is larger than Mercury and Pluto), Callisto and Europa, which are suspected to hold subsurface oceans of water.

Three new missions aim to study these moons in the coming decade. The European Space Agency (ESA’s) Jupiter Icy Moons Explorer or JUICE was launched in 2023 and will take about five years to get there. NASA’s Europa Clipper, due for launch in 2024, aims to focus on Europa when it arrives there in 2030. And the China National Space Administration’s Tianwen-4 mission will launch a Jupiter orbiter in 2029.

The key challenge will be analysing the composition of the water, which is hidden beneath several hundred kilometres of ice. Infrared and microwave cameras, among other instruments, will hopefully offer a clearer view of the moons and their planet too.

“There is still so much we don’t know about what lies beneath Jupiter’s thick gases,” says Anil Bhardwaj, director of the Physical Research Laboratory in Ahmedabad, a unit of the Government of India’s Department of Space. “We don’t know why its satellites are dominated by elements that are quite different from its own. These are some of the intriguing questions, and every mission tells us a little bit more.”