It Rains Diamonds Inside Neptune and Uranus and We Finally Understand How

Scientists have long suspected that deep within the hearts of Neptune and Uranus, it could be raining diamonds. Now, they have produced evidence showing how this could be possible.

A new study found that Neptune and Uranus likely have showers of diamonds underneath their surfaces. Source

The outer planets of our Solar System are hard to study. So far only a single space mission, Voyager 2, has flown by to reveal some of their secrets. Nevertheless, astronomers and physicists have suspected for nearly 40 years that deep within Neptune and Uranus, it rains diamonds.

The researchers’ original hypothesis was that the intense heat and pressure thousands of kilometres below the surface of these ice giants should split apart hydrocarbon compounds, with the carbon compressing into diamond and sinking even deeper towards the planetary cores. This is called the “Diamond Rain” theory.

Previously, researchers had used SLAC’s Linac Coherent Light Source (LCLS) X-ray laser so they could get an exact measurement on the creation of “warm dense matter” which is a high-pressure, high-temperature mix that scientists believed was at the core of ice giants like Neptune and Uranus. They had also used a technique called “X-ray diffraction” which takes “a series of snapshots of how samples respond to laser-produced shock waves that mimic the extreme conditions found in other planets.” This method worked very well with crystal samples but was not appropriate to examine non-crystals which possess more haphazard structures.

The extreme heat and pressurized environments of Neptune’s (pictured) interior, like Uranus, contrast with their icy exteriors. Source: NASA

Published in the journal Nature in May 2020, the new study used a different technique called “X-ray Thomson scattering” that allowed scientists to precisely reproduce diffraction results while also observing how the elements of non-crystal samples mixed together.

Using the scattering technique, researchers were able to reproduce the exact diffractions from hydrocarbon that had split into carbon and hydrogen as they would inside Neptune and Uranus. The result was the crystalization of the carbon through the environment’s extreme pressure and heat. This would likely translate into a shower of diamonds 6,200 miles underground slowly sinking toward the planets’ cores, as shown on the picture below.

This cutaway of Neptune shows the different layers of the planet, including one where diamonds may form. Models suggest the diamonds collect in a layer just above the planet’s core. Credit: Jason McAlexander

The successful laboratory experiment using the new technique will also be valuable in examining the environments of other planets.

“This technique will allow us to measure interesting processes that are otherwise difficult to recreate,” said Dominik Kraus, a scientist at Helmholtz-Zentrum Dresden-Rossendorf who led the new study. “For example, we’ll be able to see how hydrogen and helium, elements found in the interior of gas giants like Jupiter and Saturn, mix and separate under these extreme conditions.”

Illustration of the x-ray scattering technique used to study how diamonds might form inside Neptune and Uranus. HZDR/Sahneweiß

While scientists are continuing to study these phenomena in the lab, a new space probe mission to Neptune or Uranus (or both) could add a wealth of information about the planets’ internal processes – and also how such planets have formed in our Solar System and others. NASA is currently considering such a mission, as in 2030 the planets of our Solar System will be favorably aligned for a spacecraft to launch and reach Uranus or Neptune by 2040.

As such a fortuitous alignment of the planets won’t come for another two generations, now is the time to start thinking about exploring the ice giants up close and learning more about the Solar System’s intriguing diamond worlds.

Source: 1, 2, 3, 4


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