This is gross. And unsolved. But also unlikely to happen again, so don’t worry about it! — Dan

If you live in the Pacific Northwest, you get used to rain. In Oakville, Washington, a small timber town of about 700 people, precipitation falls roughly 275 days out of the year. So when police officer David Lacey was on patrol on August 7, 1994, and noticed drops hitting his windshield, he didn't think much of it. He turned on his wipers and kept on driving.

But the wipers didn’t wipe. The rain — it wasn’t water. It was goo.

Lacey immediately began investigating the mystery. He pulled over at a gas station, put on gloves (safety first!), and touched the stuff. It was goopy, translucent, and viscous — not something that typically falls out of the sky. As Mental Floss reported, each blob was about half the size of a grain of rice, but — clearly — not something you should eat.

People started failling ill anyway. Lacey himself came down with fatigue and nausea. A resident named Beverly Roberts took some of the goo home for a closer look and within a day was struck with vertigo severe enough to require medical care. Another Oakvillian, Dotty Hearn, was hospitalized with dizziness and nausea. Another, Maurice Gobeil, told Unsolved Mysteries “I got sick, my wife got sick, my daughter — everybody that lived here got sick.” Per Roberts, “everybody in the whole town came down with like a flu” — including pets.

Authorities collected samples of the goo and sent them to labs for analysis. The results only deepened the mystery. As KUOW reported, “samples were eventually sent to the Washington State Departments of Ecology and Health for testing, but the agencies came up with conflicting results: Ecology said the blobs were inorganic. DOH said they were organic.” A reporter, per KUOW, sent some goo to a private lab for another analysis; that lab determined that the substance was polyacrylamide, which is used “to prevent soil erosion; as a water treatment flocculant; oil clean up; even to stabilize cosmetics.” In other words, the mystery persisted.

Lots of theories emerged. With one lab finding enzymes that are often found in the human digestive tract, some concluded that the blobs were concentrated waste from an airplane toilet. But the Federal Aviation Administration dismissed that theory, noting that such waste is dyed blue. Another theory suggested that the blobs were jellyfish parts — the military had been conducting bombing practice runs over the Pacific Ocean at the time, and Oakville's police chief received a tip suggesting that detonating a school of jellyfish might have sent their remains into the atmosphere — preposterous, perhaps, but so is falling goo.

To date, the mystery remains unsolved, and at this point, likely unsolvable. There are no samples left to test, and unless more goo falls from the heavens, the sky has kept its secret.

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Today’s Bonus fact: While the FAA dismissed the airplane lavatory theory for the Oakville blobs because such waste is dyed blue, "blue ice" falling from planes is very much a real phenomenon. As the Los Angeles Times reported, wastewater can leak through damaged drain plugs onto the outside of aircraft, freeze at high altitudes, and then break loose during descent—plummeting to Earth at speeds approaching 100 mph. In 1989, one such chunk crashed through a California man's roof, drenching his ceiling and new mattress with what he the Times described as "a pungent mix of raw sewage and toilet-bowl cleanser." (Gross.)

From the Archives: What Do You Do With 10000 Pounds of Spoiled Mayo?: I actually use the word “goop” here, not “goo,” but close enough.

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And thanks! — Dan