The idea of using dirt on the Moon to manufacture solar cells, which could power a permanent human settlement, may seem outlandish, but two companies say they’ve made big progress on that front: they each say they’ve already made solar cells using fake Moon dirt.

Jeff Bezos’ company Blue Origin says it’s been making solar cells this way since 2021 but just made that information public in a blog post on Friday. Separately, Lunar Resources, which aims to develop technologies for the “large-scale industrialization of Space,” told The Verge in a call today that it’s been doing the same for the last couple of years.

Each company still has to make an enormous leap: from crafting solar cells out of fake dirt in Earth-bound labs to accomplishing the same thing on the harsh surface of the Moon. But this is a dream decades in the making. And if their technologies succeed, they could help make it possible to build outposts on the Moon.

The idea of tapping the Moon’s resources to support human settlements, called in-situ resource utilization (ISRU) in technical speak, has only recently moved out of the realm of science fiction. Now, with its Artemis program, NASA is looking to establish “the first long-term presence on the Moon.”

“They laughed [at ISRU] 10 years ago, they stopped laughing five years ago, and now they’re really saying, ‘Hey, this is important. We have to do it,’” says Alex Ignatiev, chief technology officer at Lunar Resources and emeritus professor of physics at the University of Houston.

Ignatiev says he proposed the idea of making solar cells using materials on the Moon to NASA 15 years ago. The project ultimately lost its funding, he says. (NASA didn’t immediately respond to a request for comment.) Since then, Ignatiev has had more luck moving the idea forward in the private sector. Lunar Resources got off the ground four years ago with funding from NASA, the Department of Defense, and the National Science Foundation.

But he says the concept came from NASA’s research into extracting oxygen out of Moon dirt, or lunar regolith. The byproducts of that process are metals and other valuable materials that Ignatiev figured you could use to make solar cells.

“The waste materials were the metals that you extracted the oxygen from. And to me, that wasn’t waste material. That was something that I can utilize,” Ignatiev tells The Verge.

The layer of “dirt” coating the Moon is nothing like Earth’s soil. The Moon has no atmosphere, so its surface is constantly pummeled by micrometeorites. The result of that pounding is lunar regolith, dirt-like debris that happens to be rich in metals and — crucially for solar cells — silicon.

The way to turn that debris into treasure, Ignatiev explains, is through a process called molten regolith electrolysis. Lunar regolith is melted at extremely high temperatures, then shot through with an electrical current to extract iron, silicon, and aluminum. (This also separates out the oxygen.) This produces the basic ingredients for making solar cells. Stitch those cells together and you then have a solar panel, and you can hypothetically keep scaling up from there.

“Our approach, Blue Alchemist, can scale indefinitely, eliminating power as a constraint anywhere on the Moon,” Blue Origin says in its February 10th announcement of the technology. Blue Origin didn’t immediately respond to a press inquiry from The Verge.

But that’s pretty big talk from a company that seemingly has yet to test its technology using real lunar dirt. There just isn’t enough of the stuff on Earth to hand it out to every commercial space company trying to run experiments with regolith. Instead, an entire cottage industry for regolith simulants has cropped up to feed those experiments. You can even buy the fake lunar dirt online. Blue Origin says it made its own regolith simulants to be “chemically and mineralogically equivalent” to the real thing, but then again, the composition of lunar regolith varies from region to region on the Moon.

Another real-world (or real-Moon) challenge will be to find a way to generate the high temperatures necessary to melt the regolith. Both Blue Origin and Lunar Resources rely on reactors to reach temperatures above 1,500 degrees Celsius. “You have to ship the tools to the Moon, right?” Ignatiev, says. “Our reactor is not small.” It weighs a ton, about 1,000 kilograms (2,204.62 pounds).

And getting people back to the Moon at all is still years away. NASA’s Artemis III Moon-landing mission has already been delayed several years, likely to 2026 at the earliest.