Geologists and planetary scientists do a lot of different things to try to understand all the processes that shape our planet and others. From sending spacecraft to the far corners of the solar system, to digging through the minerals of our planet, you never know where they will find the latest breakthroughs. And it turns out some of the most interesting results come from laboratory experiments designed to recreate the conditions of other worlds. 

In a new experiment published in Nature Astronomy and led by Tawhyun Kim, researchers studied what happens at the boundary between an ice giant’s high-pressure water layer and deeper rock layer. Ice giants like Uranus and Neptune are the most commonly discovered planets in our galaxy, and they have, for a planet, fairly straightforward structures that include an outer gas layer, ice or fluid, a rocky mantle, and then a metallic core. 

To replicate the water-rock boundary, the researchers combined rocks – olivine and ferropericlase – and water and then compressed the sample with a diamond anvil. The temperatures and pressures allowed the water to draw magnesium out of the rocks in large amounts and indicate that fluid layers in ice giants may be rich in magnesium. This is important because magnesium-rich water is a good thermal insulator. 

This may explain how Uranus, which is closer to the Sun than Neptune, is the cooler of the two worlds. According to study coauthor Sang-Heon Dan Shim, “This magnesium-rich water may act like a thermal blanket for the interior of the planet,” allowing it to block heat from escaping the interior of the planet. Here is to hoping we see more and more awesome lab science results as universities begin to reopen their facilities.

More Information

ASU press release

“Atomic-scale mixing between MgO and H2O in the deep interiors of water-rich planets,” Taehyun Kim et al., 2021 May 17, Nature Astronomy