Traces of ancient meteorites

(ORDO NEWS) — In its 4.5 billion years, the surface of the Earth has been hollowed out by hundreds of large asteroids that have crashed into its surface.

At least 190 of these collisions left colossal scars that are still visible today. But not every space rock that flies into our planet’s atmosphere reaches the ground. So what does it take for an asteroid to dent Earth, and what known impacts left the largest craters?

Asteroid bombardment

Most of the space rocks that enter the Earth’s atmosphere are not that big at all. According to NASA , they are very small – about 1 meter across. This is good for earthlings, since any space rock less than 25 meters in diameter usually does not pass through the Earth’s atmosphere.

The ultra-high speeds reached by space rocks heat up the gases in the atmosphere, which incinerate all this debris in the process. In most cases, any remnant of space rock that has passed through the atmosphere will do little to no harm if it does reach the surface.

A striking example is the 17-meter-wide meteorite that exploded over Chelyabinsk in 2013, creating a shock wave that shattered windows in houses. However, the crater did not form because the meteor did not actually touch the ground.

According to Gerhard Drolshagen, a physicist who specializes in near-Earth objects at the University of Oldenburg in Germany, most of it shattered into dust and tiny meteorites.

According to a report from the 45th Lunar and Planetary Science Conference in 2014, a 5-foot-wide meteorite at the bottom of a nearby lake, plus a few smaller fragments, is all that’s left.

But the 190 known impact craters on the Earth’s surface prove that some larger asteroids have broken through the planet’s natural defenses. Of those who landed, the majority landed in North America (32%), followed by Europe (22%), Russia and Asia (16%), according to NASA’s database.

The largest craters on earth

Of the known impact craters, 44 have a diameter of 20 kilometers or more. Here’s what we know about the three biggest impacts on land or water:

Vredefort

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According to NASA’s Earth Observatory, the largest impact crater on Earth, the Vredefort crater in South Africa, is 160 km wide and likely formed about 2 billion years ago.

The crater is largely destroyed, but based on what’s left of its rim, scientists estimate that the asteroid that hit our planet had a diameter of 10 to 15 km. “It’s bigger than the one that killed the dinosaurs, but it fell much earlier.”

According to experts, the fall of this meteor turned into a real disaster for the ancient Earth, a series of volcanic eruptions and a colossal dust cloud that darkened the light of the star for a long time.

Chicxulub

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This crater is located on the Yucatan Peninsula in Mexico and is about 180 km wide, but much younger. It was created by a 12 km wide asteroid that hit Earth 66 million years ago.

Although the crater is now partly on land, the Yucatán was under shallow water at the time of the impact. The collision resulted in the extinction of 75% of species, including non-avian dinosaurs. The impact would send a “storm” of rocks and debris into space.

Upon returning to Earth, the flaming chunks of rock likely burned much of the planet, Khodas said. The impact would also have created a cloud of dust that enveloped the Earth for years, blocking sunlight and disrupting food chains. Dinosaurs that survived the initial impact most likely starved to death en masse, Hodas said.

Sudbury Basin

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Located in Ontario, Canada, it is the third largest impact crater and, like Vredefort, is one of the oldest known impact craters on Earth.

A 2014 study found that the pool was formed not by an asteroid, but by a giant comet or a rocky mixture of asteroid fragments and ice. A space object with a diameter of 10 to 12 km collided with the Earth about 1.8 billion years ago.

Now, due to erosion, the crater is almost unrecognizable. But the extraction of nickel and iron flourishes there. “We are actually mining asteroid remnants,” Khodas said.

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