Our last EPSC story today goes farther out into our solar system to talk about ammonia mushballs at Uranus and Neptune. We’ve talked about these mushballs before with regards to Jupiter, but now scientists have found that they could solve a mystery on the two ice giants.

Remote observations of Uranus and Neptune at long wavelengths in the infrared and radio have found the two planets lack ammonia, especially compared to Jupiter and Saturn. They have a ton of methane, as expected, but not so much ammonia. And data from NASA’s Juno spacecraft has shown that ammonia is abundant at Jupiter, but also much deeper into the cloudy atmosphere than expected. This is where the idea of the ammonia mushballs came from.

As the press release explains: The Juno observations at Jupiter have shown that ammonia-water hailstones can form rapidly during storms because of ammonia’s ability to liquefy water ice crystals, even at very low temperatures of around -90 degrees Celsius. Models indicate that these mushballs in Jupiter may grow to weights of up to a kilogram or more, slightly higher than the largest hailstones on Earth. As they plunge downwards, they transport ammonia very efficiently to the deep atmosphere, where it ends up locked away beneath the cloud base.

As for the ammonia at Uranus and Neptune, presenter Tristan Guillot said: 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. Thus, ammonia is probably simply hidden in the deep atmospheres of these planets, beyond the reach of present-day instruments.

Those darn giant planets, hiding all their ammonia away from our instruments. Now we just need to send orbiters to Uranus and Neptune to confirm. I’m all for that idea.

More Information

EPSC press release