To the folks at UFO Sightings Daily, NASA’s archive of Mars images from its Curiosity rover is better than a candy shop. Every visit yields a new treat.

“Alien critter found on Mars, gazing at rover,” reads the headline on a post published Monday. If you squint at the accompanying image, which is so zoomed-in that it’s pixelated and fuzzy, you can almost see a tiny creature with spindly arms and a pumpkin-shaped head peering out from behind a rock.

Also spotted: two alien ships, a reptile head, a face looking up. And that’s just from one photo.

“There is so much evidence of intelligent life in this NASA photo, its really amazing that the public hasn’t done this kind of research long ago,” says the post’s author, Scott C. Waring.

Waring is hardly the only person to make such “discoveries.” Earlier in August, certain corners of the Internet were agog over what appeared to be a crab crawling up a Martian cliff face. Others saw a “levitating rock” in June.

Ashwin Vasavada, who works on the Mars rover project, insists that NASA scientists are not trying to hide evidence of alien life from us.

“There is no group that would be happier to see such a thing than the 500 scientists around the world who work on this Curiosity rover,” he told CNN. “So far we haven’t seen anything that is so obvious that it would be similar to what these claims are.”

When we look at chunks of space rock and piles of sand and “see” a crab, or a lizard, or an alien spaceship, we’re being tricked, he said. Not by NASA, but by our own brains.

The phenomenon is called “pareidolia,” and it explains why we so frequently find Jesus in our food, the Virgin Mary in tree trunks, a man in the moon, Hitler in teapots and tiny, pumpkin-headed aliens on Mars.

Rather than being supernatural, pareidolia is deeply biological.

It stems from a skill humans have honed over millennia of evolution, an instinctive ability to spot patterns and find the familiar that every one of us is now born with. That skill is what enables us, without thinking, to recognize things that are important — the sight of a smiling face, the sound of an alarmed voice, the low growl of a predator.

But occasionally, it leads us astray.

“We’ve evolved brains that think in these quick, dirty ways that are usually right, but at times can lead us to systematically be biased,” Christopher French, head of the Anomalistic Psychology Research Unit at Goldsmiths University of London, told the BBC in 2013. “A classic example is the Stone Age guy standing there, scratching his beard, wondering whether that rustling in the bushes really is a saber-toothed tiger. You’re much more likely to survive if you assume it’s a saber-toothed tiger and get the hell out of there — otherwise you may end up as lunch.”

Pareidolia is a consequence of our brain’s instinct to seek out meaning in ambiguous or unfamiliar images. That instinct is partly about survival — when it comes to the prospect of ending up as someone else’s meal, it’s usually better to be safe than sorry — and partly social. Humans are particularly primed to find faces in unfamiliar places because the ability to recognize a facial expression is so essential to being human. We need to know how to understand those around us and interpret their cues. As scientist Carl Sagan wrote in “The Demon-Haunted World:”

“As soon as the infant can see, it recognizes faces, and we now know that this skill is hardwired in our brains. Those infants who a million years ago were unable to recognize a face smiled back less, were less likely to win the hearts of their parents, and less likely to prosper. These days, nearly every infant is quick to identify a human face, and to respond with a goony grin.”

People who claim to find religious icons in potato ships or aliens in NASA photographs are often mocked, but psychologists say we’re all hard-wired to think this way. A 2014 study in the journal Cortex found that participants “saw” faces or letters in abstract images nearly 40 percent of the time when told that half of the photos contained more than just pure noise.

“Human brains are uniquely wired to recognize faces, so that even when there’s only a slight suggestion of facial features the brain automatically interprets it as a face,” co-author Kang Lee, a psychologist at the University of Toronto, said in a statement at the time.

Lee and his colleagues found that an area of the brain called the right fusiform gyrus was activated when the participants thought they saw a face. According to an earlier MIT study, the left fusiform gyrus is responsible for identifying possible faces, and the right side makes a split second decision about whether the object is actually a face.

Scientists still don’t entirely understand how that process works, but they know that it’s linked to dyslexia, synesthesia (the phenomenon that makes people “taste” words or associate numbers with colors) and face blindness. Even when this area is working completely normally, it can lead us to see things that aren’t really there.

Of course, pareidolia isn’t only our brain’s fault. Whether or not Jesus shows up in a slice of burnt toast depends a lot on whether we’re looking for him.

“[It] is telling you more about what’s happening with your expectations, and how you’re interpreting the world based on your expectations, rather than anything that’s necessarily in the toast,” Sophie Scott, a neuroscientist at University College London, told the BBC in 2013. “… It’s an incredibly strong demonstration of how powerful these perceptual effects are. We really want to see things like faces, we really want to hear things like voices, and our perceptual system will set out to do that.”