Huge, hundred-year storms on our gas giant neighbors might reveal clues about the weather on far-off exoplanets, scientists have found.
While we have known for a while that Jupiter's enormous, characteristic "Great Red Spot" has been raging for hundreds of years, new research has found that Saturn also possesses massive megastorms that blow for centuries.
Astronomers from the University of California, Berkeley, and the University of Michigan, Ann Arbor, studied Saturn's radio emissions and found that the planet had long-term disruptions in ammonia gas distribution consistent with the storms' effects lasting hundreds of years, a new study in the journal Science Advances stated.
These massive cyclones on Saturn are comprised primarily of hydrogen and helium gas, as well as methane, water and ammonia, and occur around once every 20 to 30 years. It now appears that the storms can last a lot longer than first thought.
They're very different from Earth hurricanes, both in terms of make-up and longevity.
Saturn's most recent storm was known as the "Great White Spot," having begun raging in late 2010, spanning nearly 200,000 miles of the huge planet's surface. These storms last for so much longer than Earth's due to the speed of the planet's orbit around the sun: Saturn takes around 29 Earth years to complete a single lap around our shared star due to being around 10 times further away. This means that its seasons each last around 7 years.
The researchers found that there were anomalies in the concentration of ammonia gas in the atmosphere, which were related to past megastorms in the planet's northern hemisphere from long ago.
"Understanding the mechanisms of the largest storms in the solar system puts the theory of hurricanes into a broader cosmic context, challenging our current knowledge and pushing the boundaries of terrestrial meteorology," lead author Cheng Li, a former 51 Peg b Fellow at UC Berkeley and current assistant professor at the University of Michigan, said in a statement.
The researchers also found that despite being cosmic neighbors, the storms on Jupiter and Saturn were different: anomalies in Jupiter's troposphere are linked to its colored bands, rather than caused by megastorms, as they are on Saturn.
"Our result shows that Saturn's tropospheric dynamics may be substantially different from Jupiter's. The Juno microwave radiometer revealed a correlation of brightness temperature anomaly with zones and belts. However, on Saturn, the brightness temperature anomalies at radio wavelengths are dominated by giant storms," the authors wrote in the paper.
This indicates that megastorm formation may be very different from planet to planet, which is an important consideration when studying exoplanets.
"At radio wavelengths, we probe below the visible cloud layers on giant planets. Since chemical reactions and dynamics will alter the composition of a planet's atmosphere, observations below these cloud layers are required to constrain the planet's true atmospheric composition, a key parameter for planet formation models," Imke de Pater, a UC Berkeley professor emerita of astronomy and of earth and planetary sciences, said in the statement.
"Radio observations help characterize dynamical, physical and chemical processes including heat transport, cloud formation and convection in the atmospheres of giant planets on both global and local scales."
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