Saturn is the second-largest planet in our solar system and one of the most fascinating ones. It has a complex and dynamic atmosphere, with swirling clouds, powerful winds, and storms that can last for months or even years. But what causes these storms, and how do they affect the planet’s environment? A new study published in the journal Science Advances on August 11, 2023, sheds some light on these questions, by using radio observations to probe below the visible cloud layers on Saturn. The study reveals that Saturn has long-lasting megastorms that can affect the distribution of ammonia gas in its atmosphere for centuries. In this article, we will explain the methods and findings of the study, and discuss their implications and significance for our understanding of Saturn’s atmosphere and weather.
How Did the Researchers Conduct the Study?
The study was conducted by astronomers from the University of California, Berkeley, and the University of Michigan, Ann Arbor, who used radio observations from the Karl G. Jansky Very Large Array (VLA) in New Mexico to study Saturn’s atmosphere. The VLA is a network of 27 radio telescopes that can work together as a single instrument to observe objects in space with high resolution and sensitivity. The VLA can detect radio waves emitted by molecules in Saturn’s atmosphere, such as ammonia, which is a key ingredient for cloud formation and weather on the planet.
The researchers used data from the VLA collected between 2010 and 2018, covering two seasons on Saturn (one season on Saturn lasts about seven Earth years). They focused on a region near Saturn’s north pole, where a giant megastorm erupted in 2010 and lasted for nine months. This storm was similar to a hurricane on Earth, but much larger and more intense. It created a huge bright spot in Saturn’s atmosphere that was visible even with small telescopes from Earth. The researchers wanted to see how this storm affected the distribution of ammonia gas below the visible cloud layers on Saturn.
What Did the Researchers Find Out?
The researchers found out that the megastorm on Saturn created a large bright band at northern latitudes that indicates a depletion of ammonia gas just below the ammonia-ice cloud, which is what we see with the naked eye. This depletion of ammonia gas lasted for hundreds of years after the storm dissipated, implying that the storm had a deep impact on the atmospheric circulation and chemistry of Saturn. The researchers also detected fainter bright bands at other latitudes that could be the remnants of older storms that occurred hundreds of years ago.
The researchers suggest that the megastorms on Saturn are driven by moist convection, similar to thunderstorms on Earth, but on a much larger scale. Moist convection occurs when warm and humid air rises from lower altitudes to higher altitudes, where it cools down and condenses into clouds and rain. On Saturn, this process involves ammonia gas, which is abundant at lower altitudes but scarce at higher altitudes. When a megastorm erupts, it brings up large amounts of ammonia gas from deep within Saturn’s atmosphere to higher altitudes, where it forms ammonia-ice clouds. This creates a bright spot in Saturn’s atmosphere that we can see from Earth. However, this also depletes the ammonia gas below the cloud layer, creating a dark spot in radio waves that we can detect with the VLA.
The researchers also propose that the difference between the storms on Saturn and Jupiter could be related to the different rotation rates and internal heat fluxes of the two planets. Jupiter rotates faster than Saturn and has more internal heat than Saturn. This means that Jupiter has stronger winds and more stable atmospheric layers than Saturn. As a result, Jupiter has a persistent anticyclone called the Great Red Spot that is 10,000 miles wide and has been observed for hundreds of years. On the other hand, Saturn has weaker winds and less stable atmospheric layers than Jupiter. This means that Saturn has more frequent and violent storms than Jupiter, but they are shorter-lived and less organized than Jupiter’s Great Red Spot.
Why Is This Study Important and What Are Its Implications?
This study is important because it contributes to our understanding of Saturn’s atmosphere and weather, which are still poorly understood compared to other planets in our solar system. By using radio observations to probe below the visible cloud layers on Saturn, the researchers were able to reveal new information about how megastorms affect the distribution of ammonia gas in Saturn’s atmosphere for centuries. This information can help us better understand how Saturn’s atmosphere works, how it evolves over time, and how it compares to other planets’ atmospheres.
This study also has implications for future research on Saturn’s atmosphere and weather. For example, it raises some questions and gaps that remain unanswered or unresolved by the study, such as:
- What causes megastorms on Saturn? What are the triggers and conditions that lead to their formation and dissipation?
- How do megastorms affect other aspects of Saturn’s environment, such as its rings, moons, and magnetosphere?
- How do megastorms compare to other types of storms in our solar system, such as the Great Red Spot on Jupiter, the hexagon on Saturn’s north pole, or the polar vortices on Earth?
- How can we improve our methods and instruments to observe and measure Saturn’s atmosphere and weather more accurately and comprehensively?
These questions and gaps provide opportunities for further research on this topic, using different data sources, methods, and models. For example, the researchers plan to use data from NASA’s Cassini spacecraft, which orbited Saturn from 2004 to 2017, to compare with the VLA data and validate their results. They also hope to use data from future missions to Saturn, such as NASA’s Dragonfly mission, which will send a drone-like rotorcraft to explore Saturn’s moon Titan in 2034.
