The icy insides of Neptune revealed

Scientists from the University of Edinburgh have revealed the chemical make-up of Neptune’s mantle.

Frozen mixtures of water, ammonia and methane make up a thick layer between the planets' atmosphere and core – known as the mantle. However, the form in which these chemicals are stored is poorly understood. Unable to recreate the planet’s conditions in the laboratory, researchers carried out computer simulations to replicate the conditions of Neptune’s mantle.

Dr Andreas Hermann, from the Centre for Science at Extreme Conditions at the University of Edinburgh, said: “Computer models are a great tool to study these extreme places, and we are now building on this study to get an even more complete picture of what goes on there."

By looking at how the chemicals there react with each other at very high pressures and low temperatures, the team was able to predict which compounds are formed in the mantle. They found frozen mixtures of water and ammonia in Neptune is likely to form a little-studied compound called ammonia hemihydrate. The compound is stable up to 500 gigapascals – pressures found within Neptune-like planets – and the researchers believe it forms an important component of icy planets.

Dr Hermann said: “This study helps us better predict what is inside icy planets like Neptune. Our findings suggest ammonia hemihydrate could be an important component of the mantle in ice giants, and will help improve our understanding of these frozen worlds.”

The study was carried out alongside scientists at Jilin University in China. The study is published in Proceedings of the National Academy of Sciences.