For longer than science fiction has even existed, humans have been fascinated with (and terrified by) the prospect of space rocks falling to Earth. But why?
There is one obvious explanation: Asteroids have fallen to Earth many times before, sometimes with devastating consequences. (RIP, dinosaurs.) But at present, there is no imminent threat of any space rock hitting Earth and causing harm. While planetary defense experts monitor near-Earth asteroids, the vast majority of wayfaring cosmic chunks either miss us completely or are small enough to burn up on their way through our planet's atmosphere.
In fact, just in case there ever were to be an asteroid that poses a threat of impacting Earth, NASA has a plan. Later this month, the agency is launching DART (Double Asteroid Redirection Test), a mission that will send a spacecraft to slam into the moonlet of a larger asteroid to see if it's possible to change the target rock's course. Neither space rock is on a trajectory to travel near Earth, but the test will see if such a technology could be useful to one day push a threatening asteroid into a new direction.
A sci-fi staple from space
Still, this is a contingency plan for an unlikely scenario, yet countless stories, books, movies and television shows continue to center around such a possible catastrophe.
From "The Day After Tomorrow" to "Greenland" and the explosive blockbuster "Armageddon," the "asteroid is coming to destroy Earth" trope is well worn. Its most recent iterations, including the upcoming "Don't Look Up" on Netflix and "Moonfall" in theaters.
In "Don't Look Up," premiering Dec. 10 on Netflix, two early-career astronomers attempt to warn humankind about a comet on its way to destroy planet Earth. (While it's not an asteroid, "space rock threatens to destroy humanity," is the crux of this sci-fi fixation." And in "Moonfall," which crashes into theaters in February 2022, things are shaken up a bit as it tells the story of the moon, rather than an asteroid, threatening to crash into Earth.
But this trend is much older than contemporary action films. Movies like "The Day the Sky Exploded" from 1958 and "The Green Slime" from 1968 are among many pillars of early science fiction that feature an asteroid threat. Even earlier, sci-fi authors like Isaac Asimov heavily featured asteroids in their work. In fact, early understandings of the asteroid belt made an appearance even earlier, in the 1895 novel "The Crack of Doom" by Robert Cromie.
Science inspires fiction
Among the many reasons why science fiction is riddled with the asteroid impact disaster trope, astronomer Amy Mainzer, the science advisor for "Don't Look Up," who served as the principal investigator of NASA's Near-Earth Object Wide-field Infrared Survey Explorer (NEOWISE) mission and who specializes in characterizing populations of asteroids and comets, shared her thoughts on why people are fascinated with asteroids in general.
"From the science standpoint, asteroids are really fascinating objects," Mainzer told Space.com. "They move and they're such a visible sign of the idea that we occupy a very active solar system and our place in the universe."
"The universe is not this sort of fixed, static, unchanging place. It really is active, things are happening all the time and we're a part of it," she added. "So I think in a lot of ways asteroids are kind of a reminder of that."
Now, while not all movies that play into this trope, Mainzer said that, at least in "Don't Look Up," the scenario presented to the audience shows "the importance of science-based decision making … it's really, at its core, a movie that speaks to the need for science-based decision making in our lives."
The evolution of asteroid threat sci-fi
Throughout the early 20th century, asteroids appeared in the media as scientists grew to understand what the asteroid belt and the space rocks that "live" there really are. But in the 1950s, the prevalence of asteroid disaster stories started to grow.
The birth of this sci-fi trope parallelled an especially tumultuous time in America, as the Cold War raged and the threat of nuclear warfare was at an all-time high following the atomic bombings of Hiroshima and Nagasaki in 1945. At this time in the U.S., schoolchildren regularly performed "duck-and-cover" drills where they would dive under their desks and cover their heads, practicing what they would do in case of a nuclear bomb being dropped.
Asteroid impacts, like nuclear weapon attacks, pose an immediate and catastrophic risk to vast areas, so it's no surprise that this trope worked its way into popular culture at this time in history.
"The earliest sci-fi stories about asteroids were more concerned with them being the result of a planetary disaster rather than the cause," Dylan Roth, a sci-fi television and film critic who explores sci-fi and the tropes that come along with it in series like "Star Trek," told Space.com. "I think the tables probably turned on this after World War II, when people were struggling to cope with the fear of a single object falling from the sky with little warning and destroying everything in a heartbeat."
Human nature also comes into play when dissecting our species' fascination with the catastrophic.
"I think the idea has a primal narrative appeal," Roth said. "The asteroid that killed the dinosaurs is the original 'villain' of life on Earth. At the same time, humanity wouldn’t be here without it. I think there’s a part of us that feels like we need to face and defeat that same threat to prove that we deserve to live here. Maybe we want to symbolically avenge the dinosaurs."
A more direct cause of its popularity, Roth pointed to the usefulness of an asteroid disaster as a plot device.
"It’s also a really simple and practical device to use for a sci-fi disaster story," he said. "It's an extinction-level threat that has no will or malice behind it. You don’t really need to dress it up — it’s a big rock from space, no further explanation necessary. It's got instant stakes, without the need to add any of the more fanciful trappings that can turn some folks off from space sci-fi."
So, being a helpful plot device that can parallel real-world fears as well as play on our most basic, instinctual human fears and feelings, will we ever stop making asteroid disaster movies?
"I don’t think we’ll stop telling stories about giant asteroid collisions unless we actually prevent one in real life. (Or, fail to prevent one, that’d definitely do the trick.)" Roth said. "If asteroid defense ever becomes a mundane reality, that’ll probably kill the romance around it to a degree. Or maybe we’ll just dream up bigger rocks to throw at ourselves. (Hello, Moonfall.)"