Diamonds Rain on More Planets Across the Universe Than Previously Thought; What Causes This Exotic Type of Precipitation?

Diamonds are known for being durable and valuable gemstones. They are used in various industries, such as automotive, electronics, and medicine. Throughout the Solar System, diamonds are known for being abundant in ice giants like Uranus and Neptune, where they fall down the sky as rain. A new study discovered that this sparkly precipitation is more common in our celestial neighborhood and elsewhere in the universe.

(Photo: Wikimedia Commons/ NASA/JPL)

How Do Diamond Rains Form?

Here on Earth, diamonds do not melt even at extremely high temperatures because they only encounter 1 atm of pressure at the Earth's surface. Meanwhile, the pressure deep inside gas giants is more than a million times greater than on our planet, and temperatures can reach more than 21,000 degrees Fahrenheit (11,000 degrees Celsius).

On icy gas planets such as Neptune and Uranus, the atmosphere is so dense that elemental carbon in the form of soot or graphite is crushed under high pressure. Combined with ultra-high temperatures, this condition allows hydrocarbons like methane to be broken down, enabling carbon atoms to connect with four others to make solid particles. As a result, carbon is linked to a crystal deep down in their atmosphere.

A Not-So-Rare Phenomenon

In a study conducted by an international team of researchers, diamond-forming processes were simulated in laboratory conditions. The experiments outlined in their research are discussed in the paper "Diamond precipitation dynamics from hydrocarbons at icy planet interior conditions."

To conduct the research, the experts used the European X-Ray Free-Electron Laser (XFEL) to monitor diamonds that form from hydrocarbon compound polystyrene film. These are pushed to enormous pressures between a vice-like setup. This configuration enabled the scientists to get a more extended look at the process than possible in previous experiments.

The drawn-out examination revealed that the temperature and pressure thresholds of diamond formation are lower than previously assumed. Although intense pressures and temperatures are required, they might not have to be as extreme as initially thought.

In terms of planets, the result of the study suggests that diamonds could form at a shallower depth than astronomers have been estimating. This means that diamond rain could be possible even on more minor gas planets, called 'mini-Neptunes, which are found to be abundant outside the Solar System.

These findings could also explain the mysteries surrounding the magnetic fields of Uranus and Neptune. Unlike Earth, giant icy planets do not have symmetrical magnetic fields, which has baffled scientists for so long.

As it turns out, diamonds could help explain this mystery, as experts suggest that magnetic fields might not be formed in the planetary core. As they drag gas and ice along with them, the descending diamond particles might be influencing the magnetic fields of these gas giants.

This groundbreaking discovery will not only deepen our knowledge of the local icy planets but also hold implications for understanding similar processes in exoplanets, according to physicist Siegfried Glenzer from the SLAC National Accelerator Laboratory.