For the first few hundred million years of our solar system, the budding Earth was a chaotic, violent place, frequently bombarded by gigantic space rocks. The relentless collisions had outsized impacts, rendering vast swaths of our planet uninhabitable for years, sometimes decades.
The global consequences of asteroid impacts are “beyond what humans can really conceive of, partly because they don’t leave obvious traces,” says Teddy Kareta, an astronomer at the Lowell Observatory in Arizona. Despite their devastating nature—or perhaps because of it—these cataclysmic events reshaped Earth’s geology and created the conditions necessary for complex life to gain a foothold, ultimately sculpting the planet into the one we know today.
Studying asteroid events on our planet allows scientists to uncover “basic aspects of the history of Earth in a way that you just can’t get otherwise,” says Kareta.
Here are seven significant asteroid events in Earth’s history.
1. 4.5 Billion Years Ago: Large Asteroid Collides Into Earth, Creates the Moon
The moon entered our solar system around 4.5 billion years ago in a truly dramatic fashion.
The prevailing theory of the moon’s origin is that a fledgling Earth was struck by a Mars-sized asteroid, known as Theia. The titanic collision blasted significant amounts of Earth’s super-heated rock into space, creating a ring of debris around the planet. Over time, this material coalesced under gravity to form the moon.
Computer simulations tracing this cosmic drama suggest that the newly formed moon would have appeared 16 times larger than it does today. This was because it orbited Earth at a much closer distance—just 15,000 to 20,000 miles away. Over millions of years, gravitational interaction between Earth and the moon caused the latter to drift a few centimeters farther away each year, a slow shift that has led to their current separation of roughly a quarter of a million miles.
As for Earth, the moon-forming collision was so powerful that it also stabilized our planet’s previously extreme axial tilt. This adjustment played a crucial role in regulating Earth’s climate and tides—key factors that ultimately created the conditions necessary for life to emerge.
Our planet’s constant surface-recycling geology has erased rock records from this era, but the moon still sports evidence of its dramatic early history, complemented with later asteroid strikes that have since pockmarked its surface.
2. 3.26 Billion Years Ago: S2 Meteorite Boosts Early Life
Asteroid impacts are often associated with destruction. Indeed, they have been detrimental to a lot of life on Earth in the past, but one particularly cataclysmic impact also provided a powerful boost for early life, says Nadja Drabon, a professor of Earth and planetary sciences at Harvard University in Massachusetts.
The space rock, about the size of four Mount Everests, crashed into a young Earth around 3.26 billion years ago, when our planet was largely a water world reigned by simple single-celled bacteria and archaea. Research led by Drabon meticulously examined remarkably well-preserved rock layers from this time in the Barberton Greenstone Belt of South Africa, revealing that the space rock had landed in the ocean, triggering mass die-offs of microorganisms that lived in shallow waters and on the few isolated islands of the time.
However, the space rock also delivered an unexpected silver lining for life as it dumped its massive reservoir of phosphorus, a vital nutrient for life, into the nutrient-starved ocean. Additionally, the impact triggered a colossal tsunami that “mixed up the ocean,” stirring up iron from the deep waters and making it accessible to surviving microorganisms, Drabon says. “That might have allowed life not only to bounce back quickly but to actually thrive after the impact.”
3. 66 Million Years Ago: Chicxulub Asteroid Wipes Out Dinosaurs
Sixty-six million years ago, a mountain-sized asteroid struck the tip of what’s now the Yucatán Peninsula of Mexico with an impact so disastrous it wiped out 70 percent of all species on our planet, including most dinosaurs.
The impact carved a 120-mile-wide bowl-shaped crater, which was named Chicxulub after a nearby coastal town. It is the second largest impact crater on Earth after Vredefort in South Africa. The crater was discovered in the late 1970s by geophysicists scouting potential locations for oil drilling. To date, half of it remains buried on the seafloor while the other half is covered with rainforest.
Fossils suggest the asteroid struck relatively shallow waters, annihilating many animals near ground zero. It also created a mega-tsunami that would have swept across the ocean in all directions and reached coastlines of the North Atlantic and South Pacific with waves higher than 10 meters (33 feet). The impact hurled chunks of the asteroid and Earth’s crust so far into space that they briefly left the atmosphere before falling back to Earth. As they re-entered, they burned up into molten droplets, igniting widespread wildfires.
Beyond the immediate destruction, the impact blanketed Earth with thick clouds of sulfur, soot and dust, blocking sunlight from reaching its surface. This plunged the planet into monthslong darkness and ground photosynthesis to a halt, disrupting the food chain that ultimately triggered the mass extinction of the dinosaurs and many other species.
Despite carrying 50 to 200 times less energy than the previous S2 impact, the Chicxulub impact “had a very dramatic effect in part because we had such complex life,” says Drabon.
4. 35 Million Years Ago: The Chesapeake Bay Crater
About 35 million years ago, an asteroid about 5 to 8 miles wide slammed into the Atlantic Ocean near present-day Virginia on the U.S. East Coast. The aftermath of this event, the 53-mile-wide Chesapeake Bay impact structure, is the largest known such crater in the U.S. and the sixth-largest in the world.
The crater is located about 200 kilometers (124 miles) southeast of Washington, D.C., and was buried within as little time as 30 minutes when impact-triggered tsunami waves washed over and filled it up. Its existence wasn’t confirmed until 1983, however, when scientists identified it through a telltale layer of molten glass particles called “tektites” in samples that were drilled from the location.
5. 50,000 Years Ago: The Barringer Crater
About 50,000 years ago, an asteroid that was about 46 meters (150 feet) wide zipped through Earth’s atmosphere and struck what is now northern Arizona. It exploded with the force of at least 2.5 million tons of TNT and left a three-quarter mile-wide crater that is possibly the best preserved impact crater on Earth.
Intriguingly, pre-existing cracks in the rock layers here caused the crater to be “closer to a square than a circle,” says Kareta.
While it is better known as the Meteor Crater, the Barringer Meteorite Crater is scientifically named in honor of Daniel Moreau Barringer, an American mining engineer and self-taught geologist who was the first to prove that a crater on Earth was caused by an asteroid impact rather than by volcanic activity or other geological processes.
Barringer’s belief that the crater was the result of a space rock striking the earth contradicted the views of many prominent scientists of his time. This hypothesis was only accepted over half a century later, when scientists recognized similarities in structure and distinct shocked minerals between the Barringer Crater and craters created by underground nuclear weapons tests conducted in Nevada during the Cold War.
Meanwhile, after two unsuccessful decades Barringer spent to find meteoritic iron in or near this crater, mining operations ceased in 1929. The crater gained a new kind of significance from 1964 onward, when test pilots-turned-astronauts trained there for Apollo moon landing missions by practicing sampling rocks and testing their moon buggies. It continues to be used as a field site for analog lunar missions to prepare astronauts for the challenges of future space exploration.
6. 1908: The Tunguska Event
On June 30, 1908, a massive 100-meter- (328 foot)-wide space rock exploded near the Tunguska River in Siberia, Russia, marking the biggest asteroid event ever witnessed on Earth.
The fireball disintegrated mid-air in a flash briefly brighter than the sun, and didn’t chisel out an impact crater. However, historical records based on limited instrumentation at the time note the shockwave from this enormous explosion created a butterfly-shaped area of destruction that killed herds of reindeer and flattened about 80 million trees.
Other testimonies of local eyewitnesses in the otherwise sparsely populated region suggest the event killed at least three people and knocked several others, including those tens of miles from the site, off their porches. The asteroid’s mid-air breakup released such a large amount of dust into the atmosphere that sunsets remained fiery red for days, and people as far away as Asia could read newspapers outdoors at midnight due to the lingering light.
Despite the dramatic nature of this event, political instability due to the start of World War I in 1914 and the Russian Revolution that soon followed hindered any serious scientific investigation at the time. It wasn't until 1927—nearly two decades after the event—that scientists were able to conduct a thorough survey of the area.
7. 2013: The Chelyabinsk Meteor
On February 15, 2013, yet another football field-sized rock struck Earth near the Chelyabinsk city in Russia. Serendipitous video recordings by dashboard cameras in cars showed a ball of bright light streaking across the sky, ending in an explosive flash that rivaled the sun as the asteroid broke up just 19 miles above the surface.While much of the asteroid’s energy was absorbed into the atmosphere, the shockwave it generated still injured about 1,500 people and damaged over 7,000 in apartments and commercial buildings.
