Home Science Ammonia-rich hail hints at Jupiter’s weather

Ammonia-rich hail hints at Jupiter’s weather

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New research suggests that the violent thunderstorms that take place in the atmosphere of Jupiter can form hail rich in ammonia, which play a key role in the atmospheric dynamics of the planet, as published in the magazine ‘JGR planets’.

This theory, developed using data from the microwave radiometer from Juno, is described in two publications directed by a researcher from the National Center for Scientific Research (CNRS), at Laboratoire Lagrange (CNRS / Observatorio de la Côte d’Azur / University of the Côte d’Azur) with the support of the National Center for Space Studies ( CNES), from France.

Water is a key substance in the meteorology of the planets and is believed to play a key role in their formation. Land storms are driven by water dynamics creating thunderstorms that are believed to be connected to regions where multiple phases of water (solid, liquid, and gas) coexist.

As on Earth, Jupiter’s water is moved by electrical storms. They are believed to form within the deep atmosphere of the planet, about 50 km below visible clouds, where the temperature is close to 0 ° C. When these storms are powerful enough, they carry water ice crystals to the upper atmosphere.

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Illustration of a Jupiter storm based on data gathered by NASA’s “Juno” mission. Image: NASA / JPL-Caltech / SwRI / MSSS / Gerald Eichstädt / Heidi N. Becker / Koji Kuramura

In the first article, researchers from the United States and Laboratoire Lagrange suggest that when these crystals interact with gaseous ammonia, the ammonia acts as antifreeze and turns the ice into liquid.

On Jupiter as on Earth, a mixture of 2/3 water and 1/3 ammonia gas will remain liquid up to a temperature of -100 ° C. Ice crystals that have risen into Jupiter’s atmosphere are melted by ammonia gas, forming a liquid of water and ammonia, and become the seeds of exotic ammonia hailstones, called ‘mushroom balls’ by the researchers.

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These balls are heavier and then fall deeper into the atmosphere until they reach a point where they evaporate. This mechanism carries ammonia and water deep into the planet’s atmosphere.

Juno’s measurements found that while ammonia is abundant near Jupiter’s equator, it is highly variable and is generally depleted elsewhere at very deep pressures. Before Juno, scientists saw evidence that parts of Jupiter’s atmosphere were depleted in ammonia at relatively shallow depths, but this had never been explained.

To explain Juno’s discovery of deep ammonia variability across most of Jupiter, the researchers developed an atmospheric mixing model that is presented in a second paper.

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Image: NASA / JPL-Caltech / SwRI / CNRS

Here they show that the presence of electrical storms and the formation of water and ammonia fungi dry the deep atmosphere of its ammonia and explain the variations observed by Juno as a function of latitude.

In a third paper, the researchers report observations of the Jovian rays from one of Juno’s cameras. The tiny sparkles appear as bright spots on cloud tops, with sizes proportional to their depth in Jupiter’s atmosphere.

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Unlike previous missions that had only observed lightning from deep regions, Juno’s proximity to the planet allowed it to detect smaller and shallower flashes. These flashes come from regions where temperatures are below -66 ° C and where water alone cannot be found in a liquid state.

However, the presence of a liquid is believed to be crucial to the ray generation process. Juno’s detection of “shallow lightning” storms at altitudes where liquid ammonia water can be created is supportive of the observation that the mushroom ball mechanism may be at work in Jupiter’s atmosphere.

Understanding the meteorology of Jupiter and other still unexplored giant planets like Uranus and Neptune should allow us to better understand the behavior of gas giant exoplanets outside our own Solar System.

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