Does It Rain Diamonds On Neptune And Uranus?

Scientists have theorised that diamonds fall on Neptune and Uranus.

“Diamonds are forever,” is a common saying which alludes to the extreme value of diamonds, which are among the rarest substance naturally found on earth. Diamonds are also one of the most valued substance on earth, partly due to its rare occurrence and partly due to the many applications the mineral has. Being the hardest naturally occurring substance on earth, the diamonds are a crucial component in the manufacture of drilling objects. Considering the high value diamonds have, it is almost unthinkable that on Uranus and Neptune, diamonds are not rare at all for they rain from the clouds. While such a scenario sounds like a script from a science fiction film, scientists have confirmed that diamonds do indeed fall from the sky on the two planets. A recent report published in the Nature Astrophysics stated that researchers at the SLAC National Accelerator Laboratory were able to form microscopic diamonds out of a piece of plastic, after recreating the extreme conditions found in the mantle of the two ice giants.

The Experiment

While the weird (or awesome) nature of space has been studied for many years, the theory of raining diamonds on Neptune and Uranus has been polarizing among astrophysicists, with some scientists discrediting the theory. The advocates of the theory have not produced convincing facts. All the experiments conducted to support the theory did not produce the required results, as researchers were not able to recreate the extreme conditions present in the mantles of Uranus and Neptune which were necessary for the formation of diamonds, where temperatures reached 5000 kelvin while pressure exceeded 700 gigapascals. That was until recently when researchers at the SLAC National Accelerator Laboratory were able to replicate the extreme pressures and temperatures of the ice giants using a high-powered optical laser, as well as an x-ray free-electron laser to send x-ray pulses at ultrafast speeds through a form of plastic, polystyrene. Polystyrene is a hydrocarbon which is made up of hydrogen and carbon atoms and has a structure which closely resembles that of the methane gas present in the giant ice planets. The researchers were excited to see microscopic diamonds forming after sending the first and second x-ray shockwave through the polystyrene. The researchers used a Linac Coherent Light Source to emit ultrafast x-ray pulses which last for less than a nanosecond (they last for a femtosecond) and was critical in recording the process which happens in an equally short duration. The study was later published in an edition of the Nature Astrophysics journal and sent the astrophysicist world into a frenzy.

Conditions On Uranus And Neptune

Uranus and Neptune as both classified as ice giants and not gas giants as they were originally thought. The two planets are the only two ice giants in the Solar System and therefore quite similar in size, appearance, and composition. Uranus is the third largest planet in the Solar System while Neptune is the Solar System’s fourth largest planet. Being mainly made up of gases, the two planets are also among the least dense planets in the Solar System. The two planets are blue in appearance, with Neptune having a darker shade of blue than Uranus. The atmospheres of the two planets are extremely thick; extending 17.2 miles on Uranus and 12.2 miles on Neptune, and are both similar in composition; made up of hydrogen, methane and helium gases. The mantles on both ice giants are made up of ices including methane, water, and ammonia. Conditions on the two planets lie in the extremes and increase in intensity closer to the cores. In Neptune, the atmospheric pressure below the lower clouds is thought to be as much as ten gigapascals and increases to about 700 gigapascals at the planet’s core with temperatures being as high as 5,400 K.

Pressures experienced in Uranus’ core are estimated to be as much as 800 gigapascals while temperatures are believed to be as much as 5,000 K. Scientists believe that conditions on the two planets’ mantle are ideal for the breakdown of methane, separating hydrogen atoms from carbon atoms and ultimately, the formation of diamonds which rain down to the planets’ cores.

First Studies

The existence of diamonds in the giant ice planets of the Solar System was first suggested by Marvin Ross, a renowned scholar who in 1981 wrote a paper entitled, “The ice layer in Uranus and Neptune—diamonds in the sky?” In the book, he stated that the interior of the two ice giants was made up of immense amounts of diamonds. Marvin Ross argued that the immense atmospheric pressure present in the interior of the planets, combined with extreme temperatures released carbon atoms from hydrogen atoms, leading to the formation of diamonds. Marvin based his argument on an experiment which involved the methane gas in a shock-wave compression procedure. Other subsequent experiments conducted by other renowned scientists such as Sandro Scandolo confirmed that at great pressure, methane gas could be transformed into hydrocarbons, with the set pressure being at least 300 gigapascals. Scientists at the University of California Berkeley who used a diamond anvil cell was able to achieve the result at temperatures of 2500 kelvins and pressures of 50 gigapascals.

These extreme temperatures and pressure are equivalent to the conditions below the clouds in Neptune. Scientists at the Geophysical Laboratory conducted another experiment in which they were able to destabilize the chemical composition of methane at temperatures of 2000 kelvins and a pressure of 7 gigapascals. However, all experiments failed to result in the formation of diamonds as the existing technology limited the levels of pressure and temperatures attained, preventing scientists from recreating the conditions present at the interior of the two ice giant planets. However, some scientists were skeptical of the theory claiming the existence of diamonds in Uranus and Neptune, stating that the presence of hydrogen and water which mixed with methane gas in the planets’ atmospheres would jeopardize the chemical reactions. Others stated that the concentration of carbon in two ice giants was not high enough to allow the formation of diamonds, regardless of the amount of pressure or temperature exerted on the gases.

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