Scientists have completed the longest-ever study of temperatures in Jupiter’s upper troposphere, the layer of the atmosphere where the giant planet’s weather occurs and where its signature colorful streaky clouds form. The work, carried out over four decades by combining data from NASA spacecraft and observations from ground-based telescopes, found unexpected patterns in how the temperatures of Jupiter’s belts and zones change over time. The study is a major step toward better understanding, and ultimately predicting, the weather on our solar system’s largest planet.
Jupiter’s troposphere has a lot in common with Earth: clouds and thunderstorms form in it. To understand this weather activity, scientists need to study certain characteristics, including wind, pressure, humidity, and temperature. Since NASA’s Pioneer 10 and 11 missions in the 1970s, they’ve known that generally cooler temperatures are associated with Jupiter’s lighter, whiter stripes (known as zones), while the darker brownish-red stripes (known as belts) are places with warmer temperatures. temperature.
However, there were not enough datasets to understand how temperatures change over the long term. The new research, published Dec. 19 in Nature Astronomy, makes a breakthrough by studying images of a bright infrared glow (invisible to the human eye) that emanates from warmer regions of the atmosphere and directly measures Jupiter’s temperatures above the colorful clouds. Scientists collected these images at regular intervals during Jupiter’s three orbits around the Sun, each lasting 12 Earth years.
In the process, they discovered that Jupiter’s temperatures rise and fall at certain periods that are not tied to the seasons or any other cycles that scientists know of. Because Jupiter has weak seasons—the planet is tilted on its axis by only 3 degrees compared to Earth’s cheerful 23.5 degrees—scientists didn’t expect Jupiter’s temperatures to change in such regular cycles.
The study also revealed a puzzling link between temperature shifts in regions thousands of miles apart: As temperatures rose at certain latitudes in the Northern Hemisphere, they fell at the same latitudes in the Southern Hemisphere—a mirror image across the equator.
“That was the most surprising of all,” said Glenn Orton, senior research scientist at NASA’s Jet Propulsion Laboratory and lead author of the study. “We found a connection between how temperatures varied at very distant latitudes. This is similar to the phenomenon we see on Earth, where weather and climate patterns in one area can have a noticeable effect on weather elsewhere, with patterns of variability seemingly ‘telelinked’ over vast distances in the atmosphere.”
The next challenge is to find out what causes these cyclical and seemingly synchronized changes. “We have now solved one part of the puzzle, which is that the atmosphere shows these natural cycles,” said co-author Leigh Fletcher of the University of Leicester in England. “To understand what drives these patterns and why they occur on these particular timescales, we need to examine both above and below the cloud layers.” One possible explanation emerged at the equator: The study authors found that temperature changes higher up, in the stratosphere, appeared to rise and fall in a pattern that is the opposite of how temperatures behave in the troposphere, suggesting that changes in the stratosphere are driving the changes. in the troposphere and vice versa.
Decades of observation
Orton and his colleagues began the study in 1978. For the duration of their research, they wrote proposals several times a year to obtain observing time at three large telescopes around the world: the Very Large Telescope in Chile, as well as NASA’s Infrared Telescope Facility. and the Subaru Telescope at the Maunakea Observatories in Hawaii.
During the first two decades of the study, Orton and his teammates took turns traveling to these observatories and collecting temperature information that would eventually allow them to connect the dots. (In the early 2000s, some telescope work could be done remotely.)
Then came the hard part—combining years of observations from multiple telescopes and scientific instruments to look for patterns. These experienced scientists were joined in their long-term study by several undergraduate interns, none of whom were born when the study began. They are students at Caltech in Pasadena, California; Cal Poly Pomona in Pomona, California; The Ohio State University in Columbus, Ohio; and Wellesley College in Wellesley, Massachusetts.
Scientists hope that this study will eventually help them predict Jupiter’s weather now that they understand it in more detail. The research could contribute to climate modeling through computer simulations of temperature cycles and how they affect weather – not just for Jupiter, but for all the giant planets in our solar system and beyond. “Measuring these temperature changes and periods over time is a step toward ultimately predicting Jupiter’s weather if we can link cause and effect in Jupiter’s atmosphere,” Fletcher said. “And the bigger question is whether we can ever extend this to other giant planets to see if similar patterns emerge.”