Why are characters’ eyes blue in Dune?

Ever since the first Dune trailer debuted, moviegoers unfamiliar with Frank Herbert’s acclaimed science-fiction novel Dune may have been confused as to why, in Denis Villeneuve’s Dune, Zendaya’s eyes are blue. She’s not alone, of course. Many of the other Fremen on the planet Arrakis suffer from the strange ocular affliction. So why does it happen?

To understand, we’ve got to talk about a key bit of Dune mythology: Spice.

[Ed. note: This piece may contain some spoilers for Dune, but mostly

Also known as melange, Spice was first introduced to the world in Herbert’s first Dune novel in 1965. The substance is produced by the Arakkis’ native sandworms, known to the Fremen as the great Shai-Hulud. Mining the stuff is fraught with challenges. There’s the brutal weather on the planet for one, but also the fact that sandworms are attracted to any rhythmic noise — like that made by machinery — and tend to show up and eat the mining equipment.

Image: Warner Bros. Pictures

But what is Spice itself like? Herbert was pretty vague in the original book. In the years that followed — in books like Dune Messiah and Children of Dune — things got a bit more specific. It’s a powdery substance, tending from orange to dark brown. It smells and tastes like cinnamon, and in the dark it glows blue. It’s also powerfully addictive; withdrawal is fatal.

Prolonged exposure also turns your eyes a deep blue — iris and sclera both. In some parts of the empire addicts wear contacts to hide their affliction. But, on the planet Arrakis, Fremen show their blue eyes with pride.

In low doses, Spice tends to bring about a slight euphoria. Longterm effects — other than the whole blue eyes thing — include increased awareness and longevity. That’s why, in the world of Dune, folks like to put it in their food and drink. It’s a popular additive all over the galaxy.

But in high doses, it gives you superpowers. Most critically for galactic society, human Navigators in the Spacing Guild immerse themselves in the stuff in order to enter the trance-like state that enables safe space travel. As a result, they become horribly mutated. The Bene Gesserit, the order of psychic, female power brokers, and the Fremen both use it to become clairvoyant, to tell the future, or to access the so-called “genetic memories” of their respective peoples.

Image: Warner Bros. Pictures

That makes Spice melange an incredibly powerful resource. The family who controls Arrakis controls the Spice, which makes them the leaders of the galaxy’s preeminent drug cartel. It also makes them the supplier of the fuel that allows for commerce and enables the military itself to do its thing.

“He who controls the Spice, controls the universe,” Baron Vladimir Harkonnen famously said in Herbert’s original book. And, if they’re getting high on their own supply, their eyes turn blue as well.

Dune on HBO Max

The epic sci-fi saga arrives to HBO Max for subscribers for free starting Oct. 21.

• HBO Max