This view compares a lucky imaging view of Jupiter from VISIR (left) at infrared wavelengths with a very sharp amateur image in visible light from about the same time (right). Credit: ESO/L.N. Fletcher/Damian Peach
Based partly on data from generations of
Jupiter’s troposphere has a lot in common with Earth’s: It’s where clouds form and storms churn. To understand this weather activity, scientists need to study certain properties, including wind, pressure, humidity, and temperature. They have known since NASA’s Pioneer 10 and 11 missions in the 1970s that, in general, colder temperatures are associated with Jupiter’s lighter and whiter bands (known as zones), while the darker brown-red bands (known as belts) are locations of warmer temperatures.
These infrared images of Jupiter with color added were obtained by the European Southern Observatory’s Very Large Telescope in 2016 and contributed to the new study. The colors represent temperatures and cloudiness: The bluer areas are cold and cloudy, and the orange areas are warmer and cloud-free. Credit: ESO / L.N. Fletcher
However, not enough data sets were available to understand how temperatures vary over the long term. The new research, published on December 19 in the journal Nature Astronomy, breaks ground by studying images of the bright infrared glow (invisible to the human eye) that rises from warmer regions of the atmosphere, directly measuring Jupiter’s temperatures above the colorful clouds. The scientists collected these images at regular intervals over three of Jupiter’s orbits around the Sun, each of which lasts 12 Earth years.
In the process, they discovered that Jupiter’s temperatures rise and fall following definite periods that aren’t tied to the seasons or any other cycles scientists know about. Because Jupiter has weak seasons – the planet is tilted on its axis only 3 degrees, compared to Earth’s jaunty 23.5 degrees – scientists didn’t expect to find temperatures on Jupiter varying in such regular cycles.
Jupiter is the fifth planet from the sun and the largest planet in the solar system. It is a gas giant with a mass about two and a half times that of all the other planets in the solar system combined. Jupiter has a thick atmosphere made up mostly of hydrogen and helium, and it has a number of distinctive features, including dark bands called “belts” and light bands called “zones.” The most famous feature of Jupiter is the Great Red Spot, a giant storm that has been raging for hundreds of years. Jupiter has 80 known moons, the four largest of which are called the Galilean moons in honor of their discoverer, Galileo Galilei. These moons are Io, Europa, Ganymede, and Callisto. Jupiter also has a number of rings, though they are much less prominent than the rings of
“We’ve solved one part of the puzzle now, which is that the atmosphere shows these natural cycles,” said co-author Leigh Fletcher of the University of Leicester in England. “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.”
One possible explanation became apparent at the equator: The study authors found that temperature variations higher up, in the stratosphere, seemed to rise and fall in a pattern that is the opposite of how temperatures behave in the troposphere, suggesting changes in the stratosphere influence changes in the troposphere and vice versa.
Decades of Observations
Orton and his colleagues began the study in 1978. For the duration of their research, they would write proposals several times a year to win observation time on three large telescopes around the world: the
Then came the hard part – combining multiple years’ worth of observations from several telescopes and science instruments to search for patterns. Joining these veteran scientists on their long-duration study were several undergraduate interns, none of whom had been born when the study began. They are students at Caltech in Pasadena, California; Cal Poly Pomona in Pomona, California; Ohio State University in Columbus, Ohio; and Wellesley College in Wellesley, Massachusetts.
Scientists hope the study will help them eventually be able to predict weather on Jupiter, now that they have a more detailed understanding of it. The research could contribute to climate modeling, with computer simulations of the temperature cycles and how they affect weather – not just for Jupiter, but for all giant planets across our solar system and beyond.
“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,” Fletcher said. “And the even bigger-picture question is if we can someday extend this to other giant planets to see if similar patterns show up.”
Reference: “Unexpected long-term variability in Jupiter’s tropospheric temperatures” by Glenn S. Orton, Arrate Antuñano, Leigh N. Fletcher, James A. Sinclair, Thomas W. Momary, Takuya Fujiyoshi, Padma Yanamandra-Fisher, Padraig T. Donnelly, Jennifer J. Greco, Anna V. Payne, Kimberly A. Boydstun and Laura E. Wakefield, 19 December 2022, Nature Astronomy.
DOI: 10.1038/s41550-022-01839-0