How many meteorites hit Earth each year?
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Each year, millions of rock fragments from outer space burn up in the Earth’s atmosphere, many of which briefly flare up and appear in the sky as “shooting stars.” But how many survived the high-velocity plunge before hitting the ground?
Rocks from outer space that land on Earth are known as meteorites. giant impactthe one that probably ended the reign of dinosaur Produced about 66 million years ago by an asteroid or comet about 6 miles (10 kilometers) in diameter is extremely rare.Instead most rocks that fall earth Very small, relatively few survive a violent dip in the Earth’s atmosphere.
Scientists estimate that fewer than 10,000 meteorites hit Earth’s land and water. Moonhas no atmosphere and gets Hit space rocks of various sizesAbout 11 to 1,100 tons (10 to 1,000 metric tons) of space rock dust per day (about 5.5 car masses), and about 33,000 ping-pong ball-sized space rock impacts per year, Live Science previously reported. did.
Related: What is the largest impact crater on Earth?
Rocks in space that usually become meteorites are known as meteoroids (small asteroids, or the smallest members of meteorites). solar systemThese range in size from megaliths about 3 feet (1 meter) wide to micrometeorites the size of a grain of dust. According to the American Meteor Society (opens in new tab)(AMS).
Meteoroids are generally fragments of asteroids or comets. However, some may be debris blown off from planets and moons. For example, more than 300 known meteorites are known to have originated as fragments. Mars, According to the Meteorological Society (opens in new tab).
When a meteor pierces the Earth’s atmosphere, it flares up from the friction of the air, creating a streak of light across the sky. These fiery falling rocks, meteorA very bright meteor is known as a fireball. According to AMS (opens in new tab)Thousands of fireballs burn across the Earth’s skies every day, but most of these occur in oceans and uninhabited areas, with a significant number shrouded in sunlight, AMS notes. .
Gonzalo Tancredi, an astronomer at the University of the Republic in Montevideo, Uruguay, said most meteors detected on Earth “come from meteor showers associated with dust ejected by comets.” However, meteor showers do not generate meteorites. That’s because the meteor bodies in such meteor showers are usually too fragile to survive falling to the ground, Tancredi told his Live Science in an email.
To estimate the number of meteorites that hit the Earth each year, Tancredi analyzed data from the Meteorological Society. From 2007 to 2018, there were 95 reports of meteor strikes on Earth, averaging about 7.9 per year.
It is impossible to know exactly how many meteorites fall into the ocean and sink undetected to the ocean floor. However, 29% of the earth’s surface is covered by land. Urban areas, where about 55% of the people live, make up about 0.44% of the land, says Tancredi.
Tancredi estimated that the total number of terrestrial meteorites that have fallen on Earth is approximately equal to the number of reported meteorites in urban areas divided by the percentage of the Earth’s land area covered by urban sprawl. did. Overall, Tancredi estimates that there are probably “about 6,100 meteorites falling across the globe each year, and about 1,800 on land.”
Tancredi pointed out that space rocks about 33 feet (10 m) wide are expected to re-enter Earth’s atmosphere every six to ten years. A rock big enough to cause an explosion like the Tunguska explosion in Russia in 1908 occurs about every 500 years, he added. A major space impact from a rock about 3,280 feet (1 km) wide is estimated to occur every 300,000 to 500,000 years. Cretaceous Dinosaurs could occur once every 100-200 million years, he said.
Originally published in Live Science.
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