Astrophysical observations have shown that Neptune-like water-rich exoplanets are common in our galaxy. These "water worlds" are believed to be covered with a thick layer of water, hundreds to thousands of miles deep, above a rocky mantle.

While water-rich exoplanets are common, their composition is very different from Earth, so there are many unknowns in terms of these planets' structure, composition and geochemical cycles.

In seeking to learn more about these planets, an international team of researchers, led by Arizona State University, has provided one of the first mineralogy lab studies for water-rich exoplanets. The results of their study have been recently published in the journal Proceedings of the National Academy of Sciences.

"Studying the chemical reactions and processes is an essential step toward developing an understanding of these common planet types," said co-author Dan Shim, of ASU's School of Earth and Space Exploration.

The general scientific conjecture is that water and rock form separate layers in the interiors of water worlds. Because water is lighter, underneath the water layer in water-rich planets, there should be a rocky layer. However, the extreme pressure and temperature at the boundary between water and rocky layers could fundamentally change the behaviors of these materials.

To simulate this high pressure and temperature in the lab, lead author and research scientist Carole Nisr conducted experiments at Shim's Lab for Earth and Planetary Materials at ASU using high pressure diamond-anvil cells.

For their experiment, the team immersed silica in water, compressed the sample between diamonds to a very high pressure, then heated the sample with laser beams to over a few thousand degrees Fahrenheit.

The team also conducted laser heating at the Argonne National Laboratory in Illinois. To monitor the reaction between silica and water, X-ray measurements were taken while the laser heated the sample at high pressures.

What they found was an unexpected new solid phase with silicon, hydrogen and oxygen all together.

"Originally, it was thought that water and rock layers in water-rich planets were well-separated," Nisr said. "But we discovered through our experiments a previously unknown reaction between water and silica and stability of a solid phase roughly in an intermediate composition. The distinction between water and rock appeared to be surprisingly 'fuzzy' at high pressure and high temperature."

The researchers hope that these findings will advance our knowledge on the structure and composition of water-rich planets and their geochemical cycles.

"Our study has important implications and raises new questions for the chemical composition and structure of the interiors of water-rich exoplanets," Nisr said. "The geochemical cycle for water-rich planets could be very different from that of the rocky planets, such as Earth."

Research paper

Related Links
Arizona State University
Lands Beyond Beyond - extra solar planets - news and science
Life Beyond Earth

Tweet

Thanks for being here; We need your help. The Space Media Network continues to grow but revenues have never been harder to maintain. With the rise of Ad Blockers, and Facebook - our traditional revenue sources via quality network advertising continues to decline. And unlike so many other news sites, we don't have a paywall - with those annoying usernames and passwords. Our news coverage takes time and effort to publish 365 days a year. If you find our news sites informative and useful then please consider becoming a regular supporter or for now make a one off contribution.
SpaceMediaNetwork Contributor $5 Billed Once credit card or paypal		SpaceMediaNetwork Monthly Supporter $5 Billed Monthly paypal only

Exoplanet apparently disappears in latest Hubble observations
Baltimore MD (SPX) Apr 21, 2020
Now you see it, now you don't. What astronomers thought was a planet beyond our solar system has now seemingly vanished from sight. Though this happens in science fiction, such as Superman's home planet Krypton exploding, astronomers are looking for a plausible explanation. One interpretation is that, rather than being a full-sized planetary object, which was first photographed in 2004, it could instead be a vast, expanding cloud of dust produced in a collision between two large bodies orbiting th ... read more