1. Juno's Journey to Jupiter
Juno was launched on August 5, 2011, and after a journey of about five years, it entered Jupiter's orbit on July 4, 2016.
The main objectives of the mission included investigating Jupiter's atmosphere, magnetic field, gravitational field, and internal structure.
2. Why Was It Necessary to Look Beneath Jupiter's Clouds?
Jupiter's visible surface is actually not a solid surface.
The planet's upper atmosphere contains dense cloud layers at different altitudes, and these clouds prevent direct observation of the atmosphere below.
Juno's scientific instruments collected information about the structure of the atmosphere by probing depths unreachable by visible light using different methods.
3. How Deep Do Jupiter's Cloud Belts Go?
The colorful belts and zones of Jupiter seen from Earth have long been considered superficial features of the planet's atmosphere.
Juno's gravity measurements showed that the eastward and westward jet streams associated with these structures extend to about 3,000 kilometers below the cloud tops.
This result revealed that atmospheric motions on Jupiter are much deeper than previously thought.
4. Deep Atmosphere with the Microwave Radiometer
Juno's Microwave Radiometer (MWR) can measure microwave radiation from Jupiter's atmosphere at different depths.
This method provided information about the distribution of gases beneath the visible clouds.
In particular, the distribution of ammonia within the atmosphere provided important clues for understanding motions in Jupiter's deep atmosphere.
5. The Unexpected Distribution of Ammonia
Juno's measurements showed that ammonia is not present in the same amount everywhere in Jupiter's atmosphere.
In some regions, the amount of ammonia decreases, while at greater depths, increases can be observed again.
This distribution indicates the presence of complex circulation systems in which gases are transported up and down within the atmosphere.
6. What Do Ammonia and Water Do Together?
Juno's observations revealed complex cloud processes in Jupiter's atmosphere where ammonia and water coexist.
Powerful storms can carry water ice crystals to high atmospheric layers.
Here, ammonia can alter the freezing and melting properties of water, contributing to the formation of a unique ammonia-water mixture not found on Earth.
7. Structures Called "Mushballs"
The ammonia-water mixture can interact with ice particles, causing the formation of heavier particles.
NASA researchers named these structures "mushballs".
These particles can fall toward deeper regions of the atmosphere, affecting the distribution of ammonia and water within the atmosphere.
8. Shallow Lightning on Jupiter
Before Juno's observations, it was thought that lightning on Jupiter occurred largely in deep water clouds.
However, Juno detected a different type of electrical discharge occurring in higher atmospheric layers.
These shallow lightning events are associated with clouds containing ammonia-water solution.
9. Giant Cyclones at Jupiter's Poles
One of Juno's most striking discoveries is the giant cyclone systems at Jupiter's poles.
It was revealed that there are giant storms at the north and south poles, some approaching the scale of Earth.
Although these storms circulate very close to each other, they can persist for long periods without fully merging into one another.
10. The Arrangement of Polar Cyclones
The storms in Jupiter's polar regions are not randomly distributed.
Especially at the north pole, a complex arrangement was observed with a central cyclone surrounded by other large cyclones.
How these systems remain stable for long periods is one of the important atmospheric questions raised by Juno's observations.
11. The Depth of the Great Red Spot
Juno's gravity and atmospheric measurements also provided new information about Jupiter's famous Great Red Spot.
It was found that this giant storm is not just a superficial spot in the atmosphere, but is connected to the deep atmospheric structure.
Juno's measurements made significant contributions to understanding the vertical structure of the Great Red Spot.
12. Jupiter's Magnetic Field
Juno's magnetometer measured Jupiter's magnetic field in unprecedented detail.
The measurements showed that the magnetic field is stronger and more irregular than expected.
In some regions, the field was measured to be much stronger, while in others it was weaker.
13. The Source of the Magnetic Field
The basis of Jupiter's strong magnetic field lies in the movement of highly electrically conductive materials deep within the planet.
In particular, liquid metallic hydrogen formed under high pressure is thought to play an important role in the dynamo process that generates Jupiter's magnetic field.
Juno's measurements indicated that some features of this magnetic field may arise at shallower depths.
14. Jupiter's Core Is Not as Expected
Juno's gravity measurements showed that the structure at Jupiter's center may be different from what was long assumed.
Instead of having a small, dense, sharply bounded solid core, the planet may have a larger, partially dissolved core structure.
This structure is sometimes described as a "fuzzy core".
15. Mapping Jupiter's Internal Structure
Juno's extremely precise measurements of the gravitational field enabled the investigation of the planet's internal mass distribution.
Features such as the depth of atmospheric jet streams and the structure of the core made it possible to infer the properties of internal layers that cannot be directly observed, thanks to these measurements.
16. Jupiter's Auroras
Juno also studied the powerful auroras at Jupiter's poles.
These emissions are linked to the interactions of charged particles in the planet's magnetosphere with the atmosphere.
Juno's measurements showed that Jupiter's auroras involve processes that differ in some important ways from Earth's polar lights.
17. Lightning at the Poles
On Earth, lightning is mostly seen in water clouds under certain temperature and humidity conditions.
On Jupiter, however, Juno's observations revealed that lightning is also common in the polar regions.
This shows that electrical processes in Jupiter's atmosphere can occur under conditions different from those on Earth.
18. Why Are Juno's Measurements Different?
Some spacecraft that previously visited Jupiter observed the planet mostly from orbits close to the equatorial plane.
Juno, however, with its pole-to-pole orbit, provided the opportunity to directly study Jupiter's poles and high latitudes.
This different perspective played an important role in the discovery of previously unseen polar storms.
19. Juno's Subsequent Observations
Juno's mission was not limited to the initial discoveries.
Results published in 2025 provided new information about the long-term movements of cyclones at Jupiter's north pole and the temperature structure of the atmosphere.
Radio occultation measurements also enabled the investigation of temperature and density variations in Jupiter's atmosphere.
20. A New Image of Jupiter's Atmosphere
Juno's data showed that Jupiter is not just a giant gas planet with colorful clouds on top, but a world where complex atmospheric motions extend thousands of kilometers deep.
The cloud belts, jet streams, ammonia circulation, giant cyclones, and magnetic field are not independent phenomena; they are physical systems connected to Jupiter's deep atmosphere and internal structure.
21. Conclusion and Evaluation
Juno's close flybys of Jupiter revealed many structures beneath the planet's thick clouds that could not previously be directly studied. The measurements showed that Jupiter's atmospheric belts and jet streams extend thousands of kilometers deep, that ammonia moves through the atmosphere in a complex way, and that there are giant cyclone systems at the poles. Previously unexpected atmospheric processes such as shallow lightning and ammonia-water mixtures were also discovered.
Juno's gravity and magnetic field measurements also revealed that the planet's internal structure is more complex than expected. Findings suggesting that Jupiter's core may be large and partially dissolved, along with detailed measurements of the strong and irregular magnetic field, contributed to the reevaluation of models of how the gas giant formed and how it operates today.
One of Juno's most important contributions is showing that Jupiter's visible clouds are actually only the upper part of a much deeper and more dynamic atmosphere.