It is always easier to blame aliens. Aliens have been used as scapegoats for everything from crop circles to missing persons. They were also for a long time blamed for a unique celestial phenomenon that many of us saw last week during an exceptional Thursday sunset. The fascinating and beautiful display was of a fallstreak hole, also known as a hole punch cloud, sky punch cloud, canal cloud, or canal hole. Fallstreak holes occur during very specific conditions and according to explainable circumstances.

Associated with cirrocumulus or altocumulus clouds, which appear as rows of layered thin, puffy clouds that stretch across the sky, the fallstreak holes develop as a circular or cigar-shaped hole in the clouds. Sometimes a rainbow can appear in the hole, making for an even more impressive show.

Sightings of fallstreak holes only go back to the 1940s, and since alien and spaceship observations have been described earlier there must be some other explanation for these openings in the clouds. Even in the late 1960s, an article in a weather publication called this phenomenon “a meteorological who done it!” 

So who or what caused them? Find fault with airplanes. 

These clouds formations contain supercooled water droplets that exhibit quite peculiar behavior. Supercooled water occurs when water droplets fall to temperatures below freezing, but remain liquid instead of forming solid ice crystals. The liquid water can reach up to negative-40 degrees Celcius and still not freeze. A suspected cause of the liquid’s longevity is that there is no solid ‘icing nuclei’ around which a solid crystal can form.

Aircraft are the catalysts believed to create the holes. When a plane flies through clouds under these conditions, it can set off a freezing process of that supercoooled liquid. The movement of the air over the plane’s wings or propeller blades causes cooling that will trigger the liquid water to freeze into crystals that will fall below the clouds, thus the name fallstreak. This process also produces just a bit of heat that will cause air to expand and rise. The freezing falling crystals and expanding rising air opens up the distinct hole in the clouds.

Fallstreak holes can spread across the sky and reach diameters of more than 30 miles across. And the angle of the plane’s crossing through the clouds can produce different shaped holes. A shallow angle leads to a longer cigar-shaped opening. Planes have also been shown to create rain and even snow when moving through clouds.

Whether it was the aliens or just an aviation anomaly, hope you were lucky enough to be outside to enjoy it on that Thursday. It is a reminder of our cause and effect; that what goes on in the heavens goes on because of an inextricable link between nature and humans.

And with us around, there will always be phenomena like this that seem otherworldly at first, but turn out to be both worldly and explainable. It’s the sheer number of bizarre things around us that surprises and humbles us, and causes us to look to the heavens for answers.

As British biologist Jack Haldane once famously stated: “the universe is not only stranger than we imagine, it’s stranger than we can imagine.”

Suzan Bellincampi is director of the Felix Neck Wildlife Sanctuary in Edgartown, and author of Martha’s Vineyard: A Field Guide to Island Nature