For years, the diamond rain in Neptune has remained a confusing mystery which scientists tried to solve and determine the reasons behind it. Eventually, a team including German and US researchers has found new evidence that explains the phenomenon.
A former study carried out in 2017 suggested that high heat and pressure at thousands of kilometers below Neptune's surface cause the interaction of hydrogen and carbon, which leads to the creation of diamond atoms. However, the new study published in the Nature Communication journal revealed a new hypothesis suggesting that carbon transitions directly into crystalline diamond.
The new experiment used the X-ray laser technique at the Linear Accelerator Center (SLAC) owned by the University of Stanford, for a simulation that provides the most precise measurements, and found that carbon transitions directly into crystalline diamond.
The atmospheres of Neptune are primarily made up of hydrogen and helium, with a small amount of methane. Below these atmospheric layers, a superhot, super dense fluid of icy materials such as water, methane, and ammonia wraps around the planet's core. It's challenging to replicate the interiors of giant planets here on Earth. You need some pretty intense equipment like those found in SLAC. And you need a material that replicates the stuff inside that giant planet. For this, the team used the hydrocarbon polystyrene in place of methane.
The first step is to heat and pressurize the material to replicate the conditions inside Neptune at a depth of around 10,000 kilometers (6,214 miles): pulses of optical laser generate shockwaves in the polystyrene, which heats the material up to around 5,000 Kelvin (4,727 degrees Celsius, or 8,540 degrees Fahrenheit). It also creates intense pressure. It produces about 1.5 million bars that is equivalent to the pressure exerted by the weight of some 250 African elephants on the surface of a thumbnail.
In a report on the Science Alert website, researcher Dominik Kraus from the Helmholtz-Zentrum Dresden-Rossendorf, Germany, said: "In the previous experiment, X-ray diffraction was used to then probe the material. This works well for materials with crystalline structures, but less so with non-crystalline molecules. So, the picture was incomplete."
But, the new experiment was more accurate in measuring how X-rays scattered off electrons in the polystyrene. "This allowed us to observe the conversion of carbon into diamond. And because carbon is denser than the material around the planet, the diamond rains occur," Kraus explained.
