Ever wished upon a shooting star? Though beautiful, shooting stars are also signs of the cosmic shooting range through which Earth is currently whizzing. The ammunition consists of countless space rocks, microscopic to mountainous, moving impossibly fast. The few that end up scoring a direct hit are called meteorites.
Organizations like NASA’s CNEOS track thousands of these near-Earth objects. Occasionally, candidates like the building-sized asteroid 2024 YR4 make headlines. In April 2025, it was announced that the asteroid has a remote chance of hitting the moon in 2032.
If humanity ever did come under threat from an extinction-level impact, pioneering experiments like the DART mission of 2022 have shown promise in diverting asteroids. But what has happened in the past when our planet faced much larger visitors from the cosmos? And how does asteroid 2024 YR4 stack up to some of astronomy’s biggest extraterrestrial impacts?
1. Chelyabinsk Meteor
Compared to ancient giant impacts, this meteor was small fry, but it still packed a devastating punch. On February 15, 2013, a 66-foot-wide hypersonic fragment called a superbolide hurtled above the Russian city of Chelyabinsk.
Its Earth-shattering speed caused the atmosphere to shred it 19 miles above the ground, creating an energetic shockwave equal to dozens of Hiroshima bombs. A 2013 paper in Science confirmed the damage. After emitting a blinding flash, the blazing rock’s explosion rattled buildings, shattered windows, and hospitalized roughly 1,500 civilians with the waves of its shrapnel.
Chelyabinsk’s meteor was unusually large but not alone. These so-called “fireballs” enter our skies fairly often, rarely hitting the surface but nonetheless making quite an impact.
Read More: Thousands Of Meteorites Hit Earth Each Year — Here’s What They Bring
2. Sudbury Basin Impact
Our next big hit occurred far before any humans or even complex life had evolved to witness it. Nearly 2 billion years ago in what is now Ontario, Canada, a presumed comet over 6 miles wide smashed into the ground. It left in its wake the Sudbury Basin, a massive oval crater almost 40 miles long.
Despite its initially violent impact, leading to ocean-churning tsunamis and globe-crossing flying wreckage, this impactor also left behind tremendous opportunity.
As the layers of melted rock cooled, they formed a concentrated layer of precious metals like nickel, copper, and even gold that would otherwise be buried deep. Thanks to this extraterrestrial impact, Ontario generates billions in annual revenue from the Basin’s riches.
3. Vredefort Crater
The Sudbury Comet, while massive, lost out on the scales to the Vredefort impactor. The culprit may have spanned over 15 miles, according to a 2022 study published in the Journal of Geophysical Research, making it the heaviest known asteroid that has ever met our planet. The clash occurred just over two billion years ago in ancient South Africa, forming the largest impact structure on Earth: a massive crater almost 200 miles across.
The energy released would make our global nuclear arsenal look like toys. The remnant of the impact, a ring of ancient crustal rocks rarely seen on the surface elsewhere, was designated a UNESCO World Heritage Site in 2005. Predictably, Vredefort Crater is now a hub of tourism and geologic research.
4. Chicxulub Impact
In the most famous cosmic catastrophe known to popular imagination, the Chicxulub Impactor ended the reign of the reptiles 66 million years ago, generating a massive crater that now rests underneath the Gulf of Mexico. A 2019 paper published in PNAS provides chilling insights into the hours following the impact. Apocalyptic tsunamis, chart-topping earthquakes, and endless wildfires greeted the life that survived.
This disaster is known in paleontology as the K-Pg mass extinction. While scientists still debate the role of longer-term climate change, the asteroid’s profound impact on ecosystems is well-supported.
Soot from wildfires and silicate dust, flung high by the collisional energy, may have created a planet-cooling blanket. Researchers, whose findings were published in Nature in 2023, modeled that global temperatures could have dropped by nearly 30 degrees Fahrenheit as plants were starved of light for years on end.
Read More: Dinosaur-Destroying Asteroid Gave Rise to Modern Rainforests
5. The Moon
Yes, you read that right. According to the leading Giant Impact Hypothesis, a Mars-sized protoplanet called Theia delivered the one impact to rule them all. Only instead of crafting a crater, it made a moon 4.5 billion years ago.
Much of Theia and the forming Earth were vaporized as the heat of impact shot out molten rock. Nonetheless, the steady hand of gravity allowed the Earth to reabsorb some of this ejecta, and a sizable portion of the rest formed the moon.
Compositional analysis demonstrates that our moon is remarkably like its parent, Earth, at the chemical level. Nonetheless, the science is far from fully settled. A 2024 paper published in Space: Science and Technology suggests numerous potential revisions to this model, including multiple smaller impacts and a much bigger Theia.
From triggering tidal waves to granting us a lunar cycle, chaotic impacts have shaped our world and will continue to do so for billions of years. As we remember the strange, alien scars of our distant past, we must also keep our telescopes trained on the future as it hurtles toward us.
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