The best space thriller on Netflix reveals a real lunar mystery

It’s a crisis unlike any we’ve ever seen on planet Earth. With annual rainfall hitting record lows, water is a scarce commodity doled out to the rich elite while the rest barely get enough to survive. Crops are failing, and children are dying at alarming rates.

The grim backdrop for Netflix’s recent Korean sci-fi thriller, The Silent Sea, might seem like an unusual one. What’s the connection between the deadly drought on Earth — likely driven by the climate crisis — and the lunar mission at the heart of this series?

But it quickly becomes clear why scientists and astronauts teamed up on this death-defying mission to the Balhae Station — a Moonbase where many people perished in a mysterious accident five years ago. It’s because there’s a coveted substance on the Moon: lunar water. As the show puts it, that lunar water could be a gift for humanity — or a deadly threat.

But is there really water on the Moon, and could it help us establish a lunar base like the one in the series? Going even further: Could we drink and maybe even mine lunar water if we ran out of water on Earth?

“Scientists are very interested in lunar water, and its use for humans,” Sara Russell, a senior research lead in planetary science at the UK’s Natural History Museum, tells Inverse.

Intrigued? Let’s dive in. (Spoilers ahead for The Silent Sea.)

Reel Science is an Inverse series that reveals the real (and fake) science behind your favorite movies and TV.

Is there water on the Moon?

In The Silent Sea, a research team of astrobiologists, doctors, engineers, and astronauts set off on a top-secret mission to recover a classified substance from the Moon. They soon discover that the substance they are after is lunar water.

As it turns out, the creators of The Silent Sea didn’t invent the concept of Moon water out of thin air, though it hasn’t always been accepted as scientific fact.

“Scientists studying lunar rocks for the first time, when the Apollo and Luna missions returned, thought the Moon seemed to be completely dry,” Russell says.

But a 2018 NASA discovery confirmed there is indeed watery ice in frozen craters located in the Moon’s polar regions. The show even references the Moon’s craters in its name. The Silent Sea is a term 17th-century astronomers used to refer to the dark spots on the Moon, which scientists now recognize as craters known as “maria.”

“The Moon seemed to be completely dry.”

Subsequent studies in 2020 have shown that water ice may be more abundant and spread across the Moon’s surface than we previously thought.

“Observations from NASA missions and other spacecraft suggest there are substantial quantities of water stored in so-called permanently shadowed regions — locations typically inside craters very close to the pole, where no sunlight has reached for at least a billion years,” Paul Hayne, an author of one of the 2020 studies and an assistant professor of astrophysical and planetary sciences at the University of Colorado, Boulder, tells Inverse.

Casey Honniball, a researcher on one of the 2020 studies and a postdoctoral fellow at NASA, tells Inverse water may have been brought to the Moon early in its history by icy bodies like comets, or perhaps even solar winds. It’s also possible micrometeorites are constantly impacting the Moon and bringing with them the chemical group hydroxyl, which then converts to water.

“Note: there is no liquid water on the Moon, and so, swimming is not a thing,” Honniball says

It’s still unclear exactly how much water there is on the Moon, though NASA is sending a rover, the Volatiles Investigating Polar Exploration Rover (VIPER), to explore the permanently shadowed regions containing water.

“There is a lot we do know and a lot we don’t know about lunar water still,” Honnibal says.

“That’s drier than the Sahara Desert.”

But there may be as much as 240,000 Olympic swimming pools worth of water, constituting roughly 160 billion gallons of water.

That’s not a lot by Earth standards.

“Outside the [permanently shadowed regions], we have measured about a 12-ounce bottle of water per cubic meter of soil. That’s drier than the Sahara Desert,” Honniball says.

But according to an email statement provided to Inverse by lunar researchers at the Planetary Science Institute, we can use remote sensing data to scout for places on the Moon that “might be useful for sustained human presence” — i.e., likely to contain water — perhaps helping us one day establish a base there similar to the one seen in The Silent Sea.

NASA is also gearing up to establish a Moonbase through its Artemis mission. Elon Musk will surely be thrilled.

Can we drink Moon water?

Drinking Moon water plays a crucial — and deadly — role in The Silent Sea. The scientists quickly discover that the coveted Moon water has dangerous effects on the human body.

“There are other volatiles besides water in the lunar cold traps. Some of these may be harmful to humans,” Hayne says. He says there may be trace amounts of the neurotoxin mercury and the dangerous compound toluene, which arrives on the Moon via comets.

There’s also likely lunar regolith — Moon soil — mixed in with the water, which would be harmful to humans.

“Regolith is really bad for humans because it’s a super fine-grained soil, almost like flour, but with really jagged edges. It can cause damage to humans if it gets into the body because of how jagged they are.

“You would need to purify it.”

But if we could filter and purify lunar water to root out these contaminants, we could probably drink it safely, unlike the characters in The Silent Sea.

“You would need to purify it by melting it and separating it from lunar regolith and any other chemicals present,” Honniball says.

After purification, the water will be the exact same as water on Earth, so there’s no reason to assume it would cause harm.

Hayne adds, “there would only be a hazard if anyone was foolish enough to drink or bathe in the water without filtering it.”

Can we mine Moon water?

Scientists in the movie predict Earth’s water supply will decrease 40 percent in the next ten years. The implication: lunar water could be examined, and, perhaps, mined to save humans from their demise.

But could we really try to mine lunar water to alleviate our current water shortages?

“The answer to this one is an unequivocal, ‘Absolutely not!” Hayne says.

The Moon’s polar ice caps have 10 billion tons of water, which “wouldn’t even put the Moon’s entire water supply in the ranking of large lakes on Earth.”

Honniball agrees. “Unfortunately, there isn’t enough water on the Moon to combat drought on Earth,” she says.

She estimates you could only provide “one-fifth of the world’s population with water for one day” using lunar water.

Hayne adds, “Frankly, the premise is ridiculous, not only for the reason that the Moon is still ‘bone dry’ compared to Earth, but also because Earth is in no danger of running out of water.”

“Earth is in no danger of running out of water.”

Even with current megadroughts, there are still probably far more Earth options — like water desalination plants — that we would try before attempting to mine water from the Moon.

While scientists are interested in Moon water, it’s mainly to beef up lunar missions — not to provide water to humans back on Earth, as The Silent Sea suggests.

“Mostly the interest is in using local water for humans already working on lunar bases, or perhaps as a “filling station” for space missions going further afield,” Russell says.

All in all, the watery advantages of Earth – including its enormously large, stable, volumes of liquid water — far outweigh any benefits of extracting water from the Moon, he says.

“Given we live on such a watery, ocean-covered planet, it is hard to see how humans could mess up Earth so badly that scavenging water from the Moon seems like a good option.”

The Silent Sea is streaming now on Netflix.