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The day in numbers: 4.5 billion

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(CNN) -- On January 18, 2000 a meteorite entered the earth's atmosphere over Canada before fragmenting and raining down across the frozen surface of Lake Tagish in British Columbia. Researchers have just announced that the meteorite remains appear to be the oldest objects ever found on earth.

4.5 billion: The estimated age of the Tagish meteorite, dating it to the very earliest days of the formation of the solar system. The meteorite contains minute grains of matter, however, that appear to be even older in date, perhaps billions of years older, and are possibly a remnant of the primordial cloud of dust that eventually coalesced to form the sun and the planets of our solar system.

410: The number of fragments of the Tagish meteorite that were documented before the spring thaw melted the surface of the lake and the meteor remains disappeared into the water below. Over 500 fragments were actually counted, and about 200 were physically recovered for more detailed examination.

5: The estimated width, in meters, of the Tagish meteorite, before it fragmented.

4.4 billion: The estimated age of the previously oldest material so far discovered on earth. Formed from the mineral zircon, it was found in western Australia.

60,000: The weight, in tonnes, of meteorite fragments that each year land on the earth's surface. The vast majority of these come down as minute particles that are neither recorded nor noticed.

60: The weight, in tonnes, of the largest meteorite ever found on earth. Consisting primarily of iron, it was found in 1920 at Hoba, Namibia.

120: The number of impact craters found on earth caused by meteor, comet or asteroid strikes.

1000: The number of asteroids of more than 1 km in width that currently orbit the earth.

180: The width, in kilometers, of the Chicxulub crater buried beneath the Yucatán Peninsula in Mexico. The crater is widely acknowledged to have been caused by a comet or asteroid strike some 65 million years ago, a collision that precipitated the end of the dinosaurs.

10: The estimated width, in kilometers, of the Chicxulub asteroid. Its collision with earth released energy equivalent to the explosion of 100,000 gigatons of TNT (the most powerful man-made explosive device ever detonated was equivalent to only one-twentieth of a gigaton).

300: The width, in kilometers, of the largest impact crater so far discovered on earth, at Vredefort in South Africa.


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