On Monday, NASA scientists announced they had detected molecular water on the Moon, trapped in ice across the lunar surface. From the data, they estimate there is some 40,000 square kilometers (more than 24,000 miles) of water on the Moon.
That much water has big implications for the ambitions to create a sustained human presence on the Moon. So can we actually drink it?
Short answer: Yes, we can, explains Shuai Li, an assistant researcher at the University of Hawaii’s Institute of Geophysics and Planetology. At least, in theory we can.
“It is water ice, the same as the water ice on Earth,” Li tells Inverse.
John Priscu, a professor at Montana University who studies the biochemistry of icy environments, agrees.
"Bottom line, if treated properly, it should be potable," he tells Inverse.
But the water on the Moon isn’t ready for astronaut's making cocktails yet.
First, scientists have to know more about what else may be swirling within that water.
What’s in the Moon water? – Water on Earth isn’t always pure. Seawater, for instance, contains about 96.5 percent water, 2.5 percent salts, and then small amounts of organic material, and other unwelcome additions like microplastics, or atmospheric gasses.
Likewise, Moon water probably isn’t pure. Li says it is probably mixed with lunar regolith — a layer of loose debris ranging from 5 meters to 10 meters deep depending on where you are on the Moon. NASA describes the lunar regolith as a “fine gray soil” made of rock fragments from the Moon itself. It also contains remnants from the bombardment of tiny meteoroids, and clumps of material formed when those meteorites melt down sections of the existing regolith.
It’s likely that this “fine gray soil” ends up in the Moon water, but it’s not clear exactly what other compounds might be in there, Li adds. He says it probably depends on what region of the Moon the water comes from.
Water pulled from the illuminated regions of the Moon (not the poles, but the pale, visible regions) may be “dominated” by anorthosite, a white, calcium-rich rock. Scientists propose that anorthosite rocks are some of the oldest on the Moon, and were created when rock-forming minerals floated to the top of a magma ocean that once engulfed the Moon about 4.5 billion years ago.
Water present in larger craters may also be exposed to basaltic materials, Li says. These are found at the bottoms of craters formed by large meteor impacts, which would have melted the rock in those areas. About 29 percent of the near side of the Moon contains basalt, but it’s only found on about 2 percent of the far side of the Moon.
If remnants of the Moon’s past and other deposits from foreign meteoroids are present in the Moon water, it may not taste great right now. (But we don’t know for sure, Li notes.)
Priscu adds the Moon water could be a bit salty if drawn from regions where the process of sublimation has allowed salts to become concentrated. Sublimation is the process by which a solid becomes a gas without passing through the liquid phase.
But if we purified it, it would likely taste fresh.
“If you can separate water from all other compounds, it will be pure water and has no taste,” Li says.
Can we get enough of the water to drink it? – Li was not involved in the NASA research published yesterday, but he has studied water on the Moon for years. In 2018, he published a paper in Proceedings of the National Academy of Sciences providing what was described as “definitive evidence” that the Moon had ice deposits on its northern and southern poles.
The poles could serve as a large water source, Li says. We need to know the thickness of the ice deposits to be sure, but Li estimates that there are “tens to hundreds of million tons of water at each pole.”
The Sun never shines on the Moon's poles, and temperatures there can dip to -250 degrees Fahrenheit. These are extreme environments and not very easily accessible.
The new papers reveal that the water sources on the Moon may not just be confined to frigid poles. Rather, the water appears scattered throughout the lunar surface in billions of tiny “cold traps,” according to one of the papers released Monday.
One cubic meter of lunar soil likely has enough water to fill a 12-ounce water bottle, Casey Honniball, a postdoctoral researcher at NASA, said at a press conference on Monday.
If we can mine it and purify it, it is quite possible that bottles of Moon water will one day quench the thirst of lunar inhabitants.