Carbon-rich exoplanets can be made of diamonds – “unlike anything in our solar system”


Illustration of a carbon-rich planet with diamonds and silica as the main minerals. Water can transform a carbide planet into a diamond-rich planet. In the interior, the main mineral will be diamonds and silica (a layer with crystals in the illustration). The core (dark blue) may be an iron – carbon alloy. Credit: Shim / ASU / Vectizy

Like mission NASAOf Hubble Space Telescope, TESS, And Kepler continue to provide insight into the properties of exoplanets (planets around other stars), scientists are increasingly able to piece together what these planets look like, what they are made of and if they are habitable or here Can even live.

In a recently published study The Planetary Science Journal, Arizona State University and a team of researchers University of Chicago It has been determined that some carbon-rich exoplanets may be made of diamonds and silica, given the right conditions.

“These exoplanets are unlike anything in our solar system,” said lead author Harrison Allen-Sutter of ASU’s School of Earth and Space Exploration.

Carbon Rich Planet Slices

An uncharged carbon planet (left) changes from a silicon carbide dominated mantle to silica and diamond dominated mantle (right). The reaction also produces methane and hydrogen. Sincerely: Harrison / ASU

Diamond exoplanet formation

When stars and planets are formed, they do so with the same cloud of gas, so their bulk compositions are the same. A star with a low carbon-to-oxygen ratio would have Earth-like planets, which would contain silicates and oxides with very low diamond content (about 0.001% of the Earth’s diamond content).

But exoplanets are more likely to contain carbon around stars with higher carbon-to-oxygen ratios than our Sun. Allen-Sutter and co-authors Emily Garht, Kurt Linenweber, and ASU’s Dan Shim, along with Vitaly Prakashenka and Aran Greenberg of the University of Chicago, hypothesized that these carbon-rich exoplanets could turn into diamonds and silicates, if water (which Is) (abundant in the universe) existed, creating a diamond-rich composition.

Diamond annals orange

In the Diamond-Evil cell, two gemstone-quality single crystal diamonds are shaped into anvils (the flat top in the photo) and then face each other. The samples are loaded between the culets (flat surfaces), then the sample is compressed between the anil. Sincerely: Shim / ASU

Diamond-Evil and X-rays

To test this hypothesis, the research team needed to mimic the interior of a carbide exoplanet using high heat and high pressure. To do this, he used high-pressure diamond-anvil cells in co-author Shim’s laboratory for material from Earth and planets.

First, he dipped silicon carbide in water and compacted the sample between diamonds at very high pressures. Then, to monitor the reaction between silicon carbide and water, they conducted laser heating at the Argonne National Laboratory in Illinois, taking X-ray measurements while the laser heated the sample at high pressure.

As they predicted, with high heat and pressure, silicon carbide reacted with water and turned to diamond and silica.

Diamond anvil sale

The cylinder-shaped objects in this picture are Diamond Evil Cells. The diamond-anvil cells are placed in copper holders and then inserted into the synchrotron X-ray / laser beam path. The photo shows diamond-anvil cells and mounts before aligning them for X-ray / laser experiments. Sincerely: Shim / ASU

Habitat and Housing

So far, we have not found life on other planets, but the search continues. Planetary scientists and astronomers are using sophisticated instruments in space and on Earth to find the right planets and planets with the correct location around their stars where life can exist.

For the carbon-rich planets that are the focus of this study, however, they do not have the necessary properties for life.

While the Earth is geologically active (an indicator of habitat), the results of this study suggest that carbon-enriched planets are too hard to be geologically active and that a lack of geological activity can make the atmospheric structure uninhabitable. Atmospheres are important to life because it provides us with air to breathe, protection from the harsh environment of space and even pressure to allow liquid water.

“Regardless of habit, this is an additional step in understanding and characterizing our ever-increasing and improved observations of exoplanets,” Allen-Sutter said. “The more we learn, the better we will be at interpreting new data from future missions to come James Webb Space Telescope And Nancy Grace Roman Space Telescope to understand the world beyond our own solar system. ”

Reference: H. Allen-Sutter, e. Garhat, K. Leninweber, v. Pratakenka, e. “Oxidation of interiors of carbide exoplanets” by Greenberg and S.H. Shim, 26 August 2020, The Planetary Science Journal.
DOI: 10.3847 / PSJ / abaa3e