Cloud gazing can be a joy and a sign of weather. It can be peaceful to watch the winds carry fluffy clouds away and beautiful to watch sunlight pass through a grey ceiling of rain clouds. More than just pleasing to watch, these clouds are signs of the atmosphere at work. In an intricate dance of air warmed by the Sun, moisture from large bodies of water, and the many intertwined air currents, the atmosphere plays a very important role in how the Earth functions.
Over centuries, we’ve learned how to understand Earth’s atmosphere through the scientific field of meteorology. But, are these atmospheric characteristics the same everywhere in the universe? Does every planet with an atmosphere have a similar meteorology as Earth? These questions become even weirder when we consider gas giants, planets that are almost entirely made of gases like hydrogen and helium. To understand how the atmospheres of gas giants shape their planetary processes, we need to closely explore them.
To do just that, scientists at NASA, the European Space Agency, and the Italian Space Agency developed a spacecraft called Cassini that they sent to Saturn back in 1997. After seven years and 2 billion miles of travel, Cassini finally reached its destination in 2004. Cassini was equipped with powerful spectrometers, cameras that can read different wavelengths of light, such as UV, radio, and visible light. By studying how light changes when it passes through different atmospheres, scientists can study the temperature of the planet, how gas molecules move, and what gases make up the atmosphere.
In the case of Saturn’s atmosphere, Cassini measured the changes in extreme UV light that passed through the atmosphere from the Sun. Extreme UV light is special because it can interact with hydrogen gas, the most common gas in the universe and in the atmosphere of Saturn. By taking pictures of the extreme UV light passing through the atmosphere, scientists could track the movement and energy of the gas particles. As the Cassini spacecraft sank into Saturn to be crushed by the giant’s massive gravity, the spacecraft made a few final measurements from deep in the atmosphere and sent all of its data to Earth.
Back home, scientists took all of the atmospheric snapshots and began sifting through them. Some data had to be removed since it was distorted when Cassini shook or had too much sunlight in the spectrometer, which blurred the data. After analyzing tens of thousands of data images, the scientists were then able to put the high quality data together to develop a history of Saturn’s atmospheric properties. Cassini had orbited from near the southern pole to the northern pole and at different altitudes in the Saturnian atmosphere.
This big picture of the data was then compared to existing atmospheric models of Saturn and revealed an interesting finding. The poles of Saturn weren’t nearly as hot as they had been predicted to be. It was assumed that like here on Earth, air currents would cycle warm air throughout the atmosphere. However, a huge portion of the atmosphere on Saturn has an air current that cycles back towards the equator before warm air can reach the poles. This difference between Saturn and Earth may be due to the sheer size of Saturn. It’s 764 times larger and is almost entirely gas, meaning there is no ocean or solid surface to stand on. Earth has oceans that can absorb heat and alter how the atmosphere cycles.
Another key finding was that Saturn has atmospheric waves. Similar to waves on the water, the gases of Saturn ripple and interact with each other, creating different effects depending on how they collide. These waves were found to disturb air circulation and can have huge effects on how temperature and wind move across the gas giant’s atmosphere, though more research is needed.
As scientists discover more planets around other stars, we are realizing how diverse they can be. Studies like this teach us more about how these planets operate and develop our understanding of our own planet. Though many questions are still left unanswered, scientists can continue analyzing the Cassini data and hope to one day send more spacecraft to the far-off space giants of our solar system.