The Great Cosmic Diamond Rush: Study says exoplanets possible with diamonds in cores but unlikely to host life

These alien worlds are likely carbon-rich and would need certain ingredients to produce the precious element: water, high heat and high pressure


                            The Great Cosmic Diamond Rush: Study says exoplanets possible with diamonds in cores but unlikely to host life
(Shim/ASU/Vecteezy)

The universe could be home to exoplanets made of diamonds, a new study suggests. These alien worlds are likely carbon-rich and would need certain ingredients to produce the precious element: water, high heat and high pressure. “These exoplanets are unlike anything in our solar system,”  lead author Harrison Allen-Sutter of ASU’s School of Earth and Space Exploration, said in a statement. On Earth, diamonds are rare, making up 0.001% of the content. They are formed 100 miles or so below the surface in the upper mantle.

"In the universe, there are about 100 billion planets in our galaxy and 100 billion galaxies in the universe," Harrison Allen-Sutter, the study's lead author and graduate assistant at Arizona State's School of Earth and Space Exploration, told Business Insider. "Even if diamond planets are only one-in-a-billion, the near unfathomably vast size of the universe means there could still be upward of trillions of diamond planets in the universe."

(Shim/ASU)

 

These diamond-rich exoplanets could be orbiting stars that have a high carbon-to-oxygen ratio. This ratio is lower on the Sun, explaining why diamonds are rare on Earth. Stars and planets are made from the same cloud of gas and dust and hence have similar composition of chemical elements, the researchers explained.

A team of researchers from Arizona State University and the University of Chicago formulated the theory that carbon-rich worlds depend on water to make diamonds. They suspect that the source of diamonds -- molten silicon carbide [containing silicon and carbon] -- is present near the core of such planets. To test the theory, the experts recreated conditions present in the interiors of carbon-rich planets in their lab. They immersed silicon carbide in water and compressed it between diamonds to very high pressure. The team used lasers to supply heat, monitoring this process with X-ray measurements. Their simulation experiment revealed that silicon carbide reacted with water to form diamonds and silica, under the right conditions of heat and pressure.

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

The carbon-rich worlds are unlikely to have the right conditions to be habitable. Unlike Earth, these worlds do not seem likely to be geologically active (an ingredient necessary for life). This lack of geologic activity may make atmospheric composition uninhabitable, the researchers said. Atmospheres not only supply the air we need to breathe, but also protect us from the harsh environment of space and provide even pressure to allow for liquid water. Missions like NASA’s Hubble Space Telescope, TESS, and Kepler have provided insights on exoplanets and their properties. In 2018, NASA said it had decided to retire the spacecraft which had made more than 2,600 planet discoveries.

"Regardless of habitability, this is one additional step in helping us understand and characterize our ever-increasing and improving observations of exoplanets," Allen-Sutter said in the statement. "The more we learn, the better we'll be able to interpret new data from upcoming future missions like the James Webb Space Telescope and the Nancy Grace Roman Space Telescope to understand the worlds beyond on our own solar system."

The study is published in The Planetary Science Journal.

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