The findings of a 40-year study of Jupiter’s atmosphere point to unusual hot and cold periods that are not tied to seasons or temperature cycles known to scientists.
If astronomers can understand the cause of these changes, it will help them predict climate patterns on Jupiter and potentially other gas giants in our Solar System.
“Measuring these temperature changes and periods over time is a step toward ultimately having a full-on Jupiter weather forecast, if we can connect cause and effect in Jupiter’s atmosphere,” said Leigh Fletcher of the University of Leicester in a statement.
“And the even bigger-picture question,” she added, “is if we can someday extend this to other giant planets to see if similar patterns show up.”
The study found that Jupiter’s temperatures rise and fall following definite periods that are outside the planet’s normal seasonal cycle. Scientists did not expect to find temperatures on Jupiter shifting in such regular cycles. Jupiter has weak seasons because it is on an axis of three degrees compared to Earth’s 23.5 degrees.
The study also found a strange connection between temperature shifts in different regions across the planet. As temperatures rose in specific latitudes in the Northern Hemisphere, they dropped at the same latitudes in the Southern Hemisphere. This was found in regions that were thousands of kilometres apart.
“That was the most surprising of all,” said Glenn Orton, senior research scientist at NASA’s Jet Propulsion Laboratory, in a statement.
“We found a connection between how the temperatures varied at very distant latitudes. It’s similar to a phenomenon we see on Earth, where weather and climate patterns in one region can have a noticeable influence on weather elsewhere, with the patterns of variability seemingly ‘teleconnected’ across vast distances through the atmosphere.”
The study began in 1978. At the time, astronomers knew Jupiter’s colder temperatures were associated with the planet’s lighter and whiter bands (known as zones), and warmer temperatures were found in darker brown-red bands (known as belts).
Astronomers did not have enough data sets to understand how temperatures varied during long-term periods. This information is critical to understanding weather activity that includes wind, pressure, humidity and temperatures.
For the first two decades of the study, the team recorded temperatures using NASA’s Infrared Telescope Facility and the Subaru Telescope (both located at the Mauna Kea Observatories in Hawaii), as well as the Very Large Telescope in Chile. The data was collected at regular intervals during three of Jupiter’s orbits around the Sun, each of which lasts 12 Earth years.
Researchers took turns travelling to those observatories, but telescope work could be done remotely by the early 2000s. Data from NASA’s spacecraft missions was also used. The research was then combined with the help of undergraduate interns who had not been born when the study began. The team was led by Orton, who published the findings with Fletcher in Nature Astronomy.
The next challenge for scientists is to learn what is causing these cyclical and seemingly synchronized changes in temperature. One theory was found while observing Jupiter’s equator, and suggests changes in the stratosphere influence changes in the troposphere — and vice versa.
“We’ve solved one part of the puzzle now, which is that the atmosphere shows these natural cycles,” said Fletcher. “To understand what’s driving these patterns and why they occur on these particular timescales, we need to explore both above and below the cloudy layers.”