Diamonds on Uranus: How it may be raining million-carat jewels on icy planets

By | 08/09/2022

Yes, there is really ‘diamond rain’ on Uranus and Neptune

This illustration shows the diamond rain on Neptune.

(Epitome credit: Greg Stewart/SLAC National Accelerator Laboratory)

The ice giants
don’t go nearly enough press; all the attention goes to their larger siblings, mighty Jupiter and magnificent Saturn.

At first glance, Uranus and Neptune are just bland, deadening balls of uninteresting molecules. But hiding beneath the outer layers of those worlds, there may exist something spectacular: a abiding rain of diamonds.


Icy planets’ diamond rain created in laser laboratory

“water ice giants” may conjure the paradigm of a Tolkien-esque creature, just it’s the proper noun astronomers use to categorize the outermost planets of the
solar arrangement, Uranus and Neptune.

Confusingly, though, the proper name has goose egg to do with ice in the sense you would normally recognize it — every bit in, say, ice cubes in your potable. The distinction comes from what these planets are made of. The gas giants of the arrangement,
Saturn, are fabricated most entirely of gas: hydrogen and helium. Information technology’s through the rapid accession of those elements that these huge planets managed to swell to their current size.

In contrast, Uranus and Neptune are fabricated by and large of h2o, ammonia and methane. Astronomers commonly call these molecules “ices,” but there actually isn’t a practiced reason for it, except that when the planets first formed, those elements were likely in solid form.

Into the (not so) icy depths

Deep beneath the green or blue cloud tops of Uranus and Neptune, there’s a lot of water, ammonia and methane. But these water ice giants probable have rocky cores surrounded by elements that are probably compressed into exotic quantum states. At some point, that quantum weirdness transitions into a super-pressurized “soup” that mostly thins out the closer you go to the surface.

But truth be told, we don’t know a lot about the interiors of the water ice giants. The terminal time we got close-up data of those two worlds was three decades ago, when
Voyager 2
whizzed by in its historic mission.

Since then, Jupiter and Saturn have played host to multiple orbiting probes, yet our views of Uranus and Neptune take been express to telescope observations.

To try to understand what’s inside those planets, astronomers and planetary scientists have to take that meager data and combine it with laboratory experiments that try to replicate the conditions of those planets’ interiors. Plus, they utilize some good old-fashioned math — a lot of it. Mathematical modeling helps astronomers understand what’s happening in a given situation based on limited data.

And it’s through that combination of mathematical modeling and laboratory experiments that we realized Uranus and Neptune might have so-chosen diamond pelting.

Astonishing photos of monster storm in Saturn’s atmosphere

It’s raining diamonds

The thought of diamond pelting was start proposed earlier the Voyager 2 mission which launched in 1977. The reasoning was pretty simple: We know what Uranus and
Neptune are made of, and we know that stuff gets hotter and denser the deeper into a planet you become. The mathematical modeling helps fill up in the details, similar that the innermost regions of the mantles of these planets likely accept temperatures somewhere around 7,000 kelvins (12,140 degrees Fahrenheit, or half-dozen,727 degrees Celsius) and pressures 6 1000000 times that of
Earth’s atmosphere.

Those same models tell us that the outermost layers of the mantles are somewhat cooler — 2,000 K (3,140 F or i,727 C — and somewhat less intensely pressurized (200,000 times Earth’s atmospheric pressure). And then, it’s natural to ask: What happens to h2o, ammonia and marsh gas at those kinds of temperatures and pressures?

With methyl hydride, in particular, the intense pressures tin can intermission the molecule apart, releasing the carbon. The carbon then finds its brethren, forming long bondage. The long bondage then squeeze together to form crystalline patterns similar diamonds.

The dumbo diamond formations so drib through the layers of the mantle until it gets too hot, where they vaporize and bladder back up and echo the cycle — hence the term “diamond rain.”

Lab-grown diamonds

The best way to validate this thought would be to send a spacecraft toUranus or Neptune. That won’t exist an option someday shortly, so we accept to go with the second-best way: laboratory experiments.

Globe, nosotros tin shoot powerful lasers at targets to very briefly replicate the temperatures and pressures institute within the water ice giants. One experiment with polystyrene (aka Styrofoam) was able to brand
nano-sized diamonds. No, Uranus and Neptune don’t comprise vast quantities of polystyrene, but the plastic was much easier than methane to handle in the laboratory and, presumably, behaves very similarly.

Also, Uranus and Neptune can proceed up those pressures for a lot longer than a laboratory laser, so the diamonds could presumably grow to exist a lot larger than nano-sized.

The end result? Based on everything we know about the composition of the water ice giants, their internal structures, results from laboratory experiments and our mathematical modeling, diamond rain is a very real affair.

Paul M. Sutter
 is an astrophysicist at


Stony Brook and the Flatiron Institute, host of “

Ask a Spaceman
and “
Space Radio
,” and author of “

How to Die in Space


Larn more by listening to the “Ask A Spaceman” podcast, available on

(opens in new tab)

. Ask your own question on Twitter using #AskASpaceman or by following Paul



Bring together our Infinite Forums to continue talking space on the latest missions, night heaven and more! And if you take a news tip, correction or comment, let us know at:

Paul M. Sutter is an astrophysicist at SUNY Stony Beck and the Flatiron Institute in New York Metropolis. Paul received his PhD in Physics from the University of Illinois at Urbana-Champaign in 2011, and spent three years at the Paris Institute of Astrophysics, followed by a enquiry fellowship in Trieste, Italy, His research focuses on many diverse topics, from the emptiest regions of the universe to the earliest moments of the Big Blindside to the hunt for the first stars. As an “Agent to the Stars,” Paul has passionately engaged the public in scientific discipline outreach for several years. He is the host of the popular “Ask a Spaceman!” podcast, author of “Your Identify in the Universe” and “How to Die in Space” and he frequently appears on Telly — including on The Weather condition Channel, for which he serves as Official Space Specialist.