NASA scientist answers: When was the last time an asteroid hit Earth?

Some 26,115 asteroids have skimmed past Earth since 1990, according to NASA’s Center for Near Earth Object Studies.

Out of those, 888 had a diameter of more than a kilometer, making them two and a half times taller than New York’s Empire State Building.

But when was the last time an asteroid actually struck the Earth?

According to NASA Jet Propulsion Laboratory scientist Marina Brozovic, the answer depends on your definition of being hit by an asteroid.

Smaller asteroids strike the Earth almost all the time, Brozovic said in NASA’s “We Asked a NASA Scientist” program. However, due to the smaller scale of those asteroids, they get burnt up in the atmosphere, so many of them don’t even reach the Earth’s surface, and rendering the impact of the rest null and void.

NASA has labeled any asteroid 140 meters or larger approaching the planet as a Potentially Hazardous Asteroid (PHA), due to having the possibility of it causing catastrophic damage to the Earth.

Asteroid illustrative (credit: Wikimedia Commons)Asteroid illustrative (credit: Wikimedia Commons)

Over the last century, the most significant asteroid to have struck the Earth was one the size of a small building that flew over Russia in 2013. That asteroid disintegrated only 20 km. above the ground, causing a large number of meteorites to scatter over the Russian city of Chelyabinsk.

But when was the last asteroid to cause a major impact on our planet, leaving craters in their wake and causing massive amounts of devastation?

“We have to go far back in time for such an event,” Brozovic answered. “Those old craters are not easy to spot.”

“By now, they are filled with sediments or they can be at the bottom of the ocean,” she said.

During the Earth’s early years, the planet was furiously bombarded by massive ancient asteroids – 10 times more often than previously believed – and may have delayed the planet from being able to support life.

However, even today, asteroids can pass by Earth without anyone even noticing.

In October, an asteroid skimmed past the Earth at just 3,000 kilometers away from the planet’s surface – less than a quarter of the planet’s diameter – but no one noticed until after the fact.

Aaron Reich contributed to this report.

Read More: NASA scientist answers: When was the last time an asteroid hit Earth?

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