Most of the time, the universe is a really confusing place.

Literally every day, there’s something that happens somewhere that scientists just can’t understand. And sometimes, things can seem so weird that it would almost make sense if they were happening on purpose, like, if they were caused by aliens.

Of course, so far, it’s never actually been aliens, but we do get tripped up every now and again. Here are three of the most puzzling times people thought we found aliens, but turned out to be wrong. Where better to start than with what was maybe the original alien signal?

Back when at least one scientist was convinced there were giant, alien-made canals on the surface of Mars. The whole episode started with a simple misunderstanding. In 1877, the Italian astronomer Giovanni Schiaparelli was the first to publish a map of Mars that was, like, at all accurate.

And he noticed and charted a number of what looked like channels, which he labeled with the Italian word canali. Unfortunately, when his map was translated into English, a sloppy translation turned canali into canals instead of channels. Although, it could have also been confused with cannoli, which would have been a lot funnier, and more delicious.

This mistranslation probably made sense to many mapmakers because the world was in the midst of a canal-building craze, like, Egypt’s Suez Canal had just been completed in 1869. So if giant, watery ditches were good enough for us Earthlings, why not for the Martians, too? In the late 1800s, it also wasn’t weird to think that Mars might be habitable, since our planets seemed similar in some ways, and no one had been there yet.

Still, all this canal talk might have stopped there if it hadn’t captured the attention of American astronomer Percival Lowell. After a few Mars observations of his own, he fell in love with the idea of alien canals and began publishing elaborate stories about a dying civilization trying to farm on a dried-out world. Kinda like astronomy fan-fiction.

Most scientists disagreed, but the idea caught on enough for papers like the New York Times to write about it seriously. Lowell even built an observatory to study the canals, but a funny thing started to happen: The closer astronomers looked, the fewer canals they could see. Almost like they didn’t exist.

Today, we know the Mars canals were just an optical illusion. Our eyes tend to try to make lines out of groups of details too fine to see, and since Mars is full of craters, mountains, and all sorts of other tiny features, it makes sense that astronomers like Lowell would have spotted canals where there weren’t any. Still, some people didn’t want to give them up, so the question wasn’t settled for good until NASA’s Mariner spacecraft actually arrived at Mars in the 1960s.

And the final verdict? Definitely no alien canals. Giant canals might’ve been the biggest alien signal we’ve ever been fooled by, but Mars has also given us the smallest.

In 1996, scientists studying a Martian meteorite, named ALH84001, made an incredible claim: They argued that this 2-kilogram hunk of Mars contained microscopic fossils of alien life. In a paper published in the journal Science, the team laid out four lines of evidence. By looking at slices of the meteorite with a microscope, they identified blob-like structures that looked a lot like tiny versions of some Earth bacteria.

The meteorite also contained traces of compounds called polycyclic aromatic hydrocarbons, which are rings of carbon sometimes created by living things. And it contained carbonite, the substance that forms marine shells and skeletons, which, despite having the same name, is not the same thing that trapped Han Solo. That stuff’s not real.

Finally, and most convincingly, were bits of magnetite, a magnetic mineral produced by some lifeforms, trapped within the carbonite. So, it seemed a lot like we found signs of life! But, it didn’t take long for scientists to do what they do best: attack those arguments.

And eventually, other researchers found explanations for how everything could have formed without life. Experiments conducted in 2001, for example, demonstrated that the conditions the meteorite would have experienced on the surface of Mars could’ve produced bits of magnetite wrapped in carbonite. Now, technically, we can’t say the meteorite doesn’t contain fossilized aliens, because this evidence could have been produced by tiny Martians, too.

But most scientists are pretty confident we haven’t found ET. Finally, not all of our so-called “evidence” of aliens comes from Mars. Sometimes, those signals come from much closer to home.

Us pesky humans were to blame for one of the weirdest-ever astronomical mysteries, called perytons. Perytons were weird, millisecond-long radio signals picked up starting in 1998 by Australia’s Parkes Observatory. They looked a lot like fast radio bursts, those mysterious signals that do come from space, but unlike FRBs, perytons would appear around the same times during the day and seemed to come from everywhere.

So… aliens? To be fair, scientists never really thought aliens were to blame, even if other people did, but it still took more than a decade to figure out what was to blame. In 2014, a special radio detector was installed which was designed to listen for Earth-based interference, and it quickly found the culprit: a perfectly ordinary microwave oven.

Really. Microwaves heat food by using, well, microwaves, which are a kind of radio wave, to excite the water molecules within the food. Normally, the machine’s outer casing keeps that energy inside... unless, of course, you get too impatient and open the door too early, because you need your Hot Pocket, like, now.

Those bursts aren’t dangerous to us, but one of the world’s most sensitive antennas had no trouble picking them up. And that caused the mysterious perytons. So, once again… we have not discovered aliens.

Yet. And if you’re wondering why we haven’t found aliens yet, well, so are we, and so was Enrico Fermi. You can learn more about his ideas in our episode on Fermi’s paradox!