Is there any physical evidence that asteroids struck our planet in the past?

While most asteroids maintain orbits within those of Mars and Jupiter, smaller groups are known to have more eccentric paths. Occasionally, asteroids large enough to survive the plunge through the atmosphere become meteorites. They can be quite destructive. Most of their impact craters have gradually wiped out by natural erosion, but two noticeable craters survive to this day.

The best known impact crater on the Earth is in Arizona, USA (Photo one). About 22,000 years ago, a mammoth iron meteorite, weighing close to 1,00,000 tonnes and having a diameter of perhaps 30 meters, broke through the atmosphere and struck the Arizona desert at over 40,000 kilometers per hour. The great blast displaced millions of tonnes of rock and dug a crater bowl over 1,219 meters in diameter and almost 186 meters deep, pushing the walls 46 meters above the surrounding plain.

The other well-preserved meteor crater is in Buldana district, Maharashtra, India (Photo two). Almost 150 meters deep with a diameter of 1.83 kilometers, this depression was caused by the impact of a small asteroid about 52,000 years ago, creating a rim almost 20 meters high. The crater is nearly filled with brackish water, forming a permanent lake known as Lonar. It is a geological wonder, though few people care to visit the site.

More reading:
Asteroid (Wikipedia)
Impact crater (Wikipedia)
Lonar crater lake (Wikipedia)

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