Recent discoveries of ammonia-rich hailstones on Jupiter, which were dubbed "mushballs", could explain why Uranus or Neptune appear to have no ammonia.
For years scientists have been puzzled by the absence of ammonia from the atmospheres of Uranus or Neptune.
Ammonia, which is well-known for its unpleasant odor, is quite common in the universe. Scientists have not been able to explain why ammonia was absent in the air of the ice giants, despite the fact that the atmospheres Uranus/Neptune are rich with other chemical compounds.
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This mystery might be solved by the recent discovery of massive, ammonia-rich hailstones at Jupiter. Warning! Spoiler alert!
NASA's Juno mission, currently orbiting Jupiter, may hold the key to this mystery.
"The Juno spacecraft showed that ammonia was present in Jupiter in abundance, but generally more [in the atmosphere] then expected," Tristan Guillot (a researcher at France's National Centre for Scientific Research, CNRS in Nice) stated in a statement.
Last year's Nature journal study found that ammonia-containing mushballs form high in Jupiter's atmosphere during thunderstorms. This is due to ammonia being able to melt ice and make liquid water in extreme cold temperatures (minus 162 degrees Fahrenheit, minus 90 degrees Celsius).
These mushballs are absorbed more ammonia as they fall through the atmosphere. They eventually accumulate up to 2.2 lbs (1 kilogram) of weight. The ammonia is transported deep into the atmosphere where it remains below the cloud base.
Guillot presented his theory at Europlanet Science Congress 2021. It was held virtualy this year, from Sept. 13 through Sept. 24.
Guillot stated that thermodynamic chemistry suggests that this process is more efficient in Uranus or Neptune and that the mushball seeds region is extended and occurs deeper.
This means that ammonia could be hidden deep within the atmosphere, much like it is on Jupiter. Earth-based telescopes allow scientists to measure the atmospheric compositions of distant planets in the solar system.
These two planets have been visited only once by a single spacecraft, NASA's Voyager 2, in the 1980s.
Guillot suggests that the intrigues of distant planets' atmospherics provide an incentive to a dedicated mission that could allow scientists to uncover all of what is going on.
Guillot stated that to fully understand these processes, we need a dedicated mission. This mission will map the deep atmosphere structure and study mixing in hydrogen atmospheres. "Neptune, Uranus, are the critical link between giant planets like Jupiter and Saturn and ice giant exoplanets we are discovering around the galaxy. It is time to get there!
