For centuries, people believed Jupiter was composed entirely of gas. Observations through telescopes and later with cameras revealed a turbulent atmospheric storm. This led to the belief it was a single, immense sphere of condensed gas. However, we now know that is not the case.
There are two theories on how Jupiter was created. The first, commonly taught in schools and called the “conventional” way, states that Jupiter formed as a large, solid core of rock and metal from collisions in the early solar system. As it became denser, it developed its own gravitational field and began attracting more material. Once massive enough, its gravity captured huge amounts of gas from the protoplanetary disc, eventually growing into what we see today.
The key point is that this theory predicts a big, dense solid core at Jupiter’s center.
There is another theory, which stands in contrast to the core-formation idea. According to this alternative, Jupiter formed more like a star: as a giant cloud of gas collapsed under its own gravity, it became a massive gas ball. Unlike the first theory, this model suggests that Jupiter did not form with a large solid core but instead formed primarily from gas, which later became part of the solar system.
The key point is that Jupiter lacks a solid core; instead, it is a layered ball of gas.
These theories are based on early observation, but like really, really early ones. Galileo was the first human to observe Jupiter using a telescope, and the first photo was taken in 1973 on the Pioneer 10 mission. It was the first mission to capture Jupiter close-up. It found the basic cloud belts, strong radiation, and a huge magnetic field. This showed that Jupiter was indeed not a giant ball of gas.
In 1979, Voyagers 1 and 2 arrived at Jupiter. They could capture images far sharper than their predecessors' and observe storms and cloud motions. They also discovered Jupiter’s rings and many more of its moons. This mattered because it revealed powerful atmospheric activity and hinted that deep winds and structure existed below the visible layer of clouds.
In 1995, Galileo (an orbiter and probe) reached Jupiter. The probe obtained the first—and so far only—direct sample of Jupiter’s atmosphere. It detected less water than expected, but we later learned it had entered a dry “hot spot,” an unrepresentative region.
The orbiter witnessed a truly rare event. The Shoemaker-Levy 9 comet was set to impact Jupiter. This event happens around every 6,000 years, and we would be alive to see it. However, we later found out that it would impact the far side of Jupiter, which we could not see from the Hubble telescope. Now, something incredibly lucky happened. The Galileo spacecraft would arrive just in time to see this event. It observed the comet hitting Jupiter and the impacts throwing materials from deeper layers upward. This means we could see what was underneath and study it.
This mission showed us that Jupiter is not the same everywhere. It really depends on where you look, because the atmosphere really differs from place to place. However, we still don’t know how much water Jupiter actually has overall. This is key to our understanding of its formation.
In the years 2000-2010, the Cassini spacecraft flew by. It observes aurorae and long-term changes in cloud cover. It received help from the Hubble Space Telescope and confirmed that Jupiter’s atmosphere is extremely dynamic and structured.
This suggests that the features we see on Jupiter's surface are driven by deep circulation and internal layers.
In 2016, the Juno spacecraft arrived and continues to operate. It measured Jupiter’s gravity by detecting subtle changes in the spacecraft’s speed to map the mass distribution. These measurements revealed asymmetries. A microwave radiometer penetrated hundreds of kilometers deep to assess water and ammonia distribution, while the magnetometer mapped Jupiter’s magnetic field in detail.
Juno therefore revealed that Jupiter does not have a small, solid core. Instead, it has a huge “fuzzy” core with heavy elements spread across a large region. Deep winds extend for thousands of kilometers, and water is unevenly distributed. The equator has more water than Galileo saw, and the magnetic field is lopsided and extremely complex.
This proves the first two theories incorrect. Jupiter does not have a big rocky core, nor is it a small hard ball. Instead, heavy elements are mixed into a giant, diluted region spanning much of the planet.
The second one fails because Jupiter contains many heavy elements (far more than the Sun does); therefore, it is not composed entirely of gas. The magnetic field is far more complex than a typical star-like collapse.
So what is Jupiter’s actual story? Based on all the observations we have at hand, the best current model is this:
Jupiter originally formed with a core, but that core later became mixed, stretched, or partly dissolved. This could be due to a massive inflow of hot gas, a major impact, or the slow erosion of the core into the surrounding metallic hydrogen.
This created today’s dilute, fuzzy core - a hybrid structure neither theory predicted.
Together, these findings reshape our understanding of Jupiter’s origins. Neither traditional theory alone explains its complex interior. Instead, Jupiter’s history reveals a rich interplay between initial core growth, dramatic mixing, and erosion, resulting in a planet with a uniquely layered and dynamic structure. This deeper insight not only changes how we view Jupiter but also broadens our perspective on how giant planets form throughout the universe.
Comments
Post a Comment