A photo of the sky in Canada's Airdrie, Alberta is baffling a lot of people on Facebook.
The photo, posted to a New Brunswick weather page, shows two clouds seemingly connected by a thin, string-like third cloud.
The page New Brunswick Weather Infocentre Météo asked its followers what they thought the strange formation could be.
Readers' opinions ranged from "aliens" and "North Korea trying to shoot a missile" to "small meteor" and "cloud birth."
The general consensus is that the photo is an optical illusion created by a jet's condensation trail. The contrail makes it seem like the bigger cloud is connected to the smaller cloud.
"That's a vapour trail from a jet and a cloud. You can't see the trail continue because of the tree. The trail is far away and cloud is closer but it just looks like something strange," Darren LeBlanc commented. Other echoed his assessment.
HuffPost Canada reached out to two meteorologists over email about the bizarre photo and they seemed to agree.
"I agree with Darren LeBlanc. It does look like a jet condensation trail - to be precise, water droplets, not "vapour," as water vapour is invisible. So, indeed, looks like an optical illusion," McGill University's Jacques Derome wrote.
Dalhousie University's Ian Folkins agreed.
"To me, the thin cloud looks like a contrail from a jet that appears to be descending to a cumulus cloud closer to the surface, but is in reality, likely around 10 km [away]. A bit of an optical illusion," he said.
So there you have it. Fortunately, aliens haven't descended upon us yet.
Also on HuffPost: