Smelly ‘mushball’ hailstones on Uranus may explain an atmospheric anomaly there


A recent discovery of giant ammonia-rich hailstones, nicknamed mushballs, on Jupiter could explain why Uranus and Neptune appear to have no ammonia in their atmosphere.

Scientists have wondered for years about the apparent absence of ammonia in the atmosphere of Uranus and Neptune.

Known for its unpleasant odor, ammonia is quite common in the universe. Since the atmospheres of Uranus and Neptune are rich in other chemical compounds known to be present in the primordial cloud hence planets trained, scientists had no good explanation for the absence of ammonia in the air of the ice giants.

Related: Could a spaceship pass through a gas giant like Jupiter?

However, a recent discovery by giant Hailstones rich in ammonia on Jupiter could shed light on this mystery. Spoiler alert! Ammonia might not be lacking at all; it may just be hidden in deeper layers of the planetary atmosphere, where current scientific instruments cannot reach.

A possible key to solving this mystery has been provided by NASA’s Juno mission, which is currently in orbit Jupiter.

“The Juno probe showed that in Jupiter, ammonia is present in abundance, but generally much deeper [in the atmosphere] than expected, “said Tristan Guillot, researcher at the National Center for Scientific Research (CNRS) in Nice. in a report.

A study published last year in the journal Nature discovered that pellets containing ammonia form in Jupiter’s atmosphere during thunderstorms thanks to the ability of ammonia to melt ice into liquid water even at temperatures extremely cold of about minus 162 degrees Fahrenheit (minus 90 degrees Celsius).

As these pellets fall into the atmosphere, they absorb more and more ammonia, eventually accumulating up to 2.2 pounds (1 kilogram) in mass. Ammonia is transported deep into the atmosphere, where it gets stuck under the base of the cloud.

“What we learned in Jupiter can be applied to provide a plausible solution to this mystery in Uranus and Neptune,” said Guillot, who presented his theory at the 2021 Europlanet Science Congress (EPSC), which was held virtually this year from September 13. to September 24.

“Thermodynamic chemistry implies that this process is even more efficient in Uranus and Neptune, and the mushball seed region is extended and occurs at greater depths,” added Guillot.

This means that, just like on Jupiter, on Uranus and Neptune, ammonia can simply be hidden deep in the atmosphere. Scientists are currently measuring the atmospheric composition of these distant planets of the solar system by analyzing the infrared and radio signatures of atmospheres by terrestrial telescopes.

These two planets have so far been visited only very briefly by a single spacecraft: that of NASA Traveler 2 in the late 1980s.

The intrigues of the atmospheres of distant planets, suggests Guillot, provide an incentive for a dedicated mission that could allow scientists to fully discover what is going on.

“To fully understand the processes, we need a dedicated mission to map the deep atmospheric structure and understand the mixing in hydrogen atmospheres,” Guillot said. “Neptune and Uranus are a vital link between giant planets, like Jupiter and Saturn, and the giant ice exoplanets that we are discovering in the galaxy. We really have to go!”

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