Mushballs—giant, slushy hailstones made from a mixture of ammonia and water—may be responsible for an atmospheric anomaly on Neptune and Uranus that has been puzzling scientists. A study presented by Tristan Guillot at the Europlanet Science Congress (EPSC) 2021 shows that mushballs could be highly effective at carrying ammonia deep into the ice giants' atmospheres, hiding the gas from detection beneath opaque clouds.