Can You Drink Saturn's Rings?

Scientific American

11 hours ago

In November 2024 I was interviewed for a marvelous NPR podcast called Living On Earth about my latest popular science book, Under Alien Skies. While prepping for the show, one of the producers asked me a question that was so deceptively simple, so wonderfully succinct, and came from such an odd direction that I was immediately enamored with it.
Can you drink Saturn's rings?
After pausing for a moment to savor the question, I replied with one of my favorite responses as a scientist and science communicator: 'I don't know. But I'll try to find out.'
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So I did. And to my delight, the nuanced answer I found is another personal favorite: Yes! But no. Kinda. It depends.
I love this sort of answer because it arises when the science behind a seemingly easy question is very much not so simple.
So please grab a frosty glass of (locally sourced) ice water, sit back and let me explain.
Saturn's rings were likely first seen by Galileo in 1610. His telescope was fairly low-quality compared with modern equipment. And through its optics, all he could see were a pair of blobs, one on each side of the planet's visible face; he referred to them as Saturn's 'ears.'
It wasn't until a few decades later that astronomers realized these 'ears' were actually a planet-encircling ring. Much was still unclear, but one thing was certain: the ring couldn't be solid. The speed at which an object orbits a planet depends on its distance from that world, and Saturn's ring was so wide that the inner edge would orbit much more rapidly than its outer edge, which would shear anything solid apart.
Astronomers came up with a variety of different ideas for the structure, including a series of solid ringlets or even a liquid. It wasn't until the mid-1800s that the great Scottish physicist James Clerk Maxwell proved none of these would be stable and instead proposed what we now know to be true: the structure around Saturn was made of countless small particles, which were far too tiny to be seen individually from Earth.
Further, these small objects form not just one ring but several, and these major rings are designated by letters in order of their discovery. The A ring is the outermost bright ring. Just interior to it is the bright and broad B ring, which contains most of the entire ring system's mass. Interior to that is the darker C ring, which leads down to the faint D ring that extends almost to the upper atmosphere of Saturn itself. In total these rings stretch across nearly 275,000 kilometers—two thirds of the Earth-moon distance! Despite their immense sprawl, the rings are almost impossibly flat, in many places just about 10 meters thick. Seen exactly edge-on, they look like a narrow line cutting across the planet.
But what are they made of? Observations over the centuries have revealed that the main constituent of the rings is startlingly simple: water ice! Good ol' frozen H 2 O is extremely common in the outer solar system and makes up most of many moons and other small bodies there.
In fact, in situ observations performed by the Cassini spacecraft— which orbited Saturn for more than a dozen years — showed that in some places the rings were made of almost perfectly pure water ice. Even better, most of the ring bits are a few centimeters across or smaller—the size of ice cubes, so they're already conveniently packaged.
Sounds great! All you need to do then is scoop up some chunks, warm them—a lot (the average temperature of the rings is about –190 degrees Celsius)—and have yourself a nice, refreshing sip.
But not so fast. This is where it gets more complicated. The spectra of the rings also show that they aren't made of absolutely pure ice. There's other material in the rings, and even though we're typically talking about contamination of less than 1 percent by mass, it's not clear what this stuff is. Scientists' best guess is that it comes from the impacts of micrometeorites, tiny particles whizzing around the outer solar system. This material is therefore likely composed of silicates (that is, rocks) or abundant metals, namely iron.
Neither of these will harm you, although the U.S. Environmental Protection Agency recommends no more than 0.3 milligram of iron per liter of potable water (to avoid a metallic taste). You'd better run a magnet over your ring water before you drink it—and you should probably filter out any silicate sediments while you're at it.
On the other hand, the rings' spectra suggest the presence of some unknown carbon-based contaminants as well. One likely candidate would be complex organic molecules called polycyclic aromatic compounds, or PAHs, which are relatively prevalent in space; many giant stars blow out PAH-laced winds as they die. One molecule that is commonly present in PAHs is cyanonaphthalene, which is considered carcinogenic. (It's unclear, though, how much exposure poses risks to humans —or, for that matter, whether this specific molecule actually exists in the rings.)
It's best to be cautious and avoid these potential contaminants by picking your rings carefully. The abundance of water ice is highest in the outer A and middle B rings, for example, whereas the C and D rings appear to be the most contaminated. So, generally speaking, it'd probably be better to opt for ice from A or B while skipping C and D entirely.
There could also be other ices in the rings, too, including frozen methane and carbon dioxide. Methane should bubble out when the ice is liquefied, and of course CO 2 is what makes carbonated beverages fizzy. That might actually add a fun kick to drinking from the rings!
There are other rings, too, outside the major ones we've already mentioned. For example, Saturn's icy moon Enceladus boasts dozens of geysers that blast liquid water from its interior out into space. This material forms a faint, fuzzy ring (the E ring) that, again, is mostly water ice but also contains small amounts of silicates—and noxious ammonia—so I wouldn't recommend it.
Still, all in all, it looks like— if carefully curated and cleaned —Saturn's rings are indeed drinkable!
How much water is there in the rings, then? The total mass of the rings is about 1.5 × 10 19 kilograms, which, correcting for the density of ice and the removal of contaminants, should yield about 10 quintillion liters of water—enough to keep every human on Earth well hydrated for more than a million years.
Eventually, if and when humans start to ply the interplanetary space-lanes, they'll need extraterrestrial sources of water because lifting it from Earth is difficult and expensive. Saturn's rings might someday become a popular rest stop. And, oh my, what a view visitors would have as they filled up!