Giant ‘mushroom balls’ could hide missing ammonia on Neptune and Uranus

One of the advantages of planetary science is that information from one planet could explain phenomena on another. We understand the greenhouse effect of Venus from our own experience on Earth, and Jupiter and Saturn share some characteristics.

But Jupiter also provides insight into other more distant systems, such as Uranus and Neptune.

Now, a discovery of a spacecraft orbiting Jupiter could have solved a long-standing mystery about Uranus and Neptune – where did all the ammonia go?

Scientists have long noticed an absence of ammonia in the atmospheres of Uranus and Neptune compared to the amounts observed on Jupiter and Saturn.

Many considered this fact strange because the models of planetary formation suggested that all gas giants originated from the same “primordial soup”, so their compositions should be similar.

Theories abounded as to where the ammonia had gone, but closer inspection of Jupiter itself hints at a potential explanation.

Juno, a probe currently exploring Jupiter’s system, noticed that ammonia in the upper atmosphere formed “balloons” as it merged with water also present in the atmosphere.

Like hailstones, these hailstones are more liquid than traditional hailstones because ammonia liquefies water even at extremely low temperatures, like those found in Jupiter’s upper atmosphere.

These amalgamated mushballs can grow bigger than some of the biggest hailstones on Earth. They are also prone to fall quickly into the atmosphere, dragging their building blocks out of the upper part of the atmosphere.

As they get closer to the center of Jupiter, the temperature rises, vaporizing ammonia and water and allowing them to ascend to the upper observable parts.

(NASA / JPL-Caltech / SwRI / CNRS)

According to Tristan Guillot of CRNS Laboratoire Lagrange, the same process could occur on Neptune and Uranus, but the balls of balls retain ammonia longer in the lower atmosphere, without as much chance of releasing it at observable altitudes.

At such low altitudes, ammonia appears to be lacking with current observation capabilities. The upper layers of cloud would obscure any ammonia readings, making it look like it’s gone.

To see the ammonia disappeared, it would take a mission specifically dedicated to the exploration of the low atmospheres of the outer planets. Some missions have been touted in the past, but none are currently operational.

As Dr Guillot points out, understanding the outer planets of our own solar system would help us understand the atmospheres of exoplanets far beyond our own solar system. Maybe it’s time to send a dedicated probe to find out more about our most distant planetary neighbors.

This article was originally published by Universe Today. Read the original article.