Hailstorms on Jupiter Pelt Giant Slushee Balls of Ammonia and Water

The weather on Jupiter may, in some ways, resemble phenomena on Earth, but there are peculiarities that completely defy our understanding.

The “Mushball” Hypothesis

Scientists now propose an explanation for the strange properties of the planet’s chaotic clouds: during massive thunderstorms with lightning and thunder, Jupiter is bombarded by a rain of mushballs large clumps of slushy ice made of ammonia and water, with a texture similar to wet snow or a convenience store slushie.

This is currently the best hypothesis astronomers have to explain the uneven distribution of ammonia in Jupiter’s atmosphere something that also occurs on Saturn, Uranus, and Neptune.

Imke [de Pater] and I thought, ‘There’s no way this could be real, said Chris Moeckel, planetary scientist at the University of California, Berkeley, who led the research. So many variables need to align for this to work — it seemed incredibly exotic. I spent three years trying to prove it wrong. And I couldn’t.

The idea first surfaced in 2020, when data from the Juno probe suggested a strange mechanism behind the removal of ammonia and water from the planet’s upper atmosphere.

According to this theory, Jupiter’s massive storms fling water high into the atmosphere, where it meets ammonia vapor that melts the ice. The mixture then refreezes in the extreme cold, forming mushballs.

At those altitudes, ammonia acts as an antifreeze, lowering the melting point of water and allowing the formation of ammonia-water liquid clouds, explained Heidi Becker from NASA’s Jet Propulsion Laboratory.

These falling droplets of ammonia and water can collide with rising ice crystals and electrify the clouds — which was surprising, since ammonia-water clouds don’t exist on Earth.”

Investigating the Storm with Juno and Hubble

To investigate further, Moeckel and his colleagues — Imke de Pater (UC Berkeley) and Huazhi Ge (Caltech) — analyzed data from Juno and the Hubble Space Telescope from July 2017, when the probe passed over a massive lightning storm that’s still active today.

Juno recorded data in six radio frequencies with its microwave radiometer, while Hubble captured images in ultraviolet, optical, and near-infrared wavelengths.

Jupiter’s atmosphere is extremely turbulent, with multiple storms happening at once. However, most of the weather systems are relatively shallow. A recent study reveals that many weather patterns extend only 10 to 20 kilometers below the visible cloud tops.

Some systems, however — such as cyclonic vortices, ammonia-rich cloud bands, and violent lightning storms where mushballs form — reach much deeper into the troposphere.

“Most of what we see on Jupiter is surface-level. It’s shallow, but a few things — vortices and big storms — break through that layer,” Moeckel said. “We’re basically showing that the top of the atmosphere doesn’t accurately represent what’s going on deeper inside.”

These mushball storms disrupt the atmosphere’s composition. As mushballs form and fall, they deplete ammonia up to about 150 kilometers deep while transporting it further into Jupiter’s interior.

Previously, scientists had no explanation for where the ammonia was going. Mushballs provide the missing piece. Water rises from deep in the atmosphere, mixes with ammonia in a ratio of 3:1, freezes, and falls back down, releasing its contents deeper in the planet.

Strict Conditions Required

This process requires very specific conditions: powerful updrafts to lift the water and rapid mixing to form large, dense mushballs that can survive the fall.

The key evidence came from Juno’s radio data.

There was a small spot beneath the cloud that looked like cooling — melting ice — or an ammonia spike — melting and releasing ammonia, said Moeckel. The fact that either explanation only made sense with mushballs is what finally convinced me.

This transport mechanism may not be unique to Jupiter. Scientists believe similar processes could be occurring on the other gas giants — and even on exoplanets. Let’s hope future missions can confirm it.

Read the original article on: Science Alert

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