Major storms on Jupiter can leave a fingerprint in the planet's atmosphere

Jupiter’s colossal storms leave lasting imprints on the planet’s atmosphere, altering its chemical composition. Recent research leveraging data from NASA’s Juno spacecraft and the Hubble Space Telescope reveals how these powerful Jovian storms churn the gas giant’s atmosphere to surprising depths. This atmospheric upheaval involves storms dredging up ammonia in some regions and propelling it downward as slushy hailstones in others, fundamentally reshaping the planet’s atmospheric makeup.

Evidence suggests that substantial storms on Jupiter can generate a conspicuous impact on the planet’s gaseous envelope.

A contemporary study utilized data from the Juno orbiter and the Hubble Telescope to investigate the mechanisms by which storms agitate the gas giant’s atmosphere, extending surprisingly deep beneath the cloud layers. This process involves storms drawing up ammonia in certain locations while casting it into the Jovian depths as dense, slushy hailstones in other areas.

Consequently, swathes of ammonia gas become entrenched deep within portions of Jupiter’s lower atmosphere, while other zones exhibit significantly diminished ammonia levels compared to typical amounts. Effectively, certain storms on Jupiter can establish a distinct signature, transforming the overall chemical structure of the planet’s atmosphere.

Jupiter’s Storm Systems: An In-depth Look

A significant tempest on Jupiter erupted in December 2016, situated just south of the planet’s equator and roughly 60 degrees east of the renowned Great Red Spot. Amateur astronomer Phil Miles initially detected this storm in February 2017, with impeccable timing.

Juno was poised to execute its fourth close flyby of Jupiter, and the Atacama Large Millimeter/submillimeter Array (ALMA) on Earth, along with the orbiting Hubble Space Telescope, were also directed towards the gas giant. This alignment enabled astronomers to observe Jupiter across diverse light wavelengths concurrently.

Equipped with information from three observatories, planetary scientist Chris Moeckel from the University of California, Berkeley, and his team embarked on determining the updrafts, downdrafts, and heat transfer processes that best accounted for the observations from Juno, Hubble, and ALMA during and after the storm. Their simulations of Jupiter’s atmospheric dynamics revealed that the massive storm had disturbed the planet’s atmosphere extending dozens of miles below the lowest cloud formations.

To fully grasp the implications, understanding a peculiarity in describing Jupiter’s weather patterns is essential.

Measuring altitude within Jupiter’s atmosphere presents challenges because the planet lacks a solid surface in the conventional sense. While liquid layers exist beneath the extensive gaseous strata, direct measurements remain elusive. Consequently, scientists employ pressure as a proxy for depth. A specific level in Jupiter’s middle stratosphere exhibits atmospheric pressure akin to Earth’s sea level, providing a convenient reference point for gauging depth within Jupiter’s atmosphere. The dense, water vapor clouds, where massive Jovian storms originate, reside approximately 82 miles (132 kilometers) below this reference level, characterized by air pressure roughly tenfold greater than Earth’s sea-level pressure.

Furthermore, Juno data indicates that the lowest cloud formations during the early 2017 storm extended several miles beneath even this benchmark level. Therefore, in the storm’s aftermath, the atmosphere had been disturbed to considerable depths, far below the cloud layers.

Storm Dynamics: Updrafts, Downdrafts, and Ammonia

Juno and Hubble imagery from 2017 captured evidence of a potent updraft near the storm’s core. This updraft propelled ammonia from deep within Jupiter’s atmosphere, surging upwards towards the crests of towering storm clouds. Beneath this plume, observations from Juno and Hubble revealed that the updraft had depleted a significant amount of ammonia from a region of Jupiter’s atmosphere extending at least tens of miles below the base of the storm clouds.

Surrounding the bright updraft zone, darker patches evident in Juno’s data indicated downdrafts transporting a slushy mixture of ammonia and water back into the Jovian depths. Astonishingly, the ammonia plummeted to atmospheric layers much deeper than initially anticipated by Moeckel and his colleagues.

Had the 2017 storm clouds merely released substantial liquid ammonia droplets as rain, these droplets should not have penetrated far into the atmosphere before encountering higher temperatures and pressures that would cause evaporation. The resulting ammonia gas would then linger, forming a new gaseous layer. However, the ammonia descended to greater depths – simulations suggest depths where atmospheric pressure is roughly 30 times Earth’s sea-level pressure. This implies that the storm likely discharged substantial, slushy conglomerates of mixed water and ammonia, often termed “mush balls”.

Mush Balls and Deep Atmospheric Ammonia

Mush balls represent a peculiar meteorological phenomenon on Jupiter, initially theorized (also using Juno data) several years prior.

Ammonia remains liquid at considerably lower temperatures than water. This property enables liquid ammonia droplets to integrate with icy water crystals within Jupiter’s storm clouds. The resultant mixture is a slushy aggregation, possessing just enough solidity to maintain cohesion but notably softer than a typical hailstone – analogous to a wet snowball. Mush balls precipitating from a storm can descend at much greater velocities than raindrops, enabling them to penetrate significantly deeper before succumbing to evaporation.

Consequently, deep within Jupiter’s atmosphere, patches of ammonia exist that originated as mush ball precipitation from storms raging miles above. This ammonia remains trapped at these depths until subsequent major storms dredge it upwards.

The scientific community received these findings on March 28 with their publication in Science Advances.