Incoming! A look at meteorites

The meteor strike in Chelyabinsk, Russia caused worldwide attention, but it was hardly The Big One.

A hundred-thousand space rocks plummet directly toward Earth every year, experts estimate. Most of those burn to bits; only about 500 actually hit Earth's surface.

The oceans swallow 357, leaving 143 on dry land, but only five to six per year are big enough to be seen out on the ice sheets of Antarctica — the best hunting-grounds for meteorites — or the deserts of Libya, Oman, Australia, and the US.

Of course, five to six per year can add up to a lot of meteorites over thousands and millions of years. The international Meteoritical Society is responsible for keeping a catalogue of all collected meteorites, named after the places where they fell: As of 2002, 44,963 entries were officially validated.

By the catalogue's standards, Chelyabinsk was big. At 56 feet across, it was about the size of a boxcar. By one definition, it actually was an asteroid; indeed, it was about a third the size of a much-scrutinized asteroid known as 2012 DA14 that NASA was monitoring carefully for its possible effects on Earth, while not having seen Chelyabinsk at all.

Weighing 10,000 tons, Chelyabinsk entered Earth's atmosphere at 40,000 mph — 50 times the speed of Mach 1 — and released half a megaton of energy above the ground — or 25 times the energy of the nuclear bomb dropped on Nagasaki, equivalent to 20 kilotons of TNT. NASA estimates that an impact of Chelyabinsk's size happens about once a century.

For comparison, the 1908 Tunguska meteor, which exploded three to six miles above the Earth, also in Siberia, was 330 feet across, and released 750 times the energy of the Nagasaki bomb. This was the largest explosion in recorded history.

Evidence is accumulating that a lake near the Tunguska epicenter may be the crater, but not all the proof is in. Finally, Meteor Crater in Arizona, now a tourist destination, was created 50,000 years ago by a meteorite 164 feet across, weighing 300,000 tons, that entered Earth's atmosphere at 28,600 mph and released about 10 megatons of energy close to the ground, or 500 Nagasaki bombs.

Still, Siberia and Arizona are far away. Has a meteorite ever hit Milford?

Two centuries ago, a 330 pound meteorite exploded 10 miles in the air above Weston, Connecticut, the largest chunk of 44 pounds hitting a farmer's field in Easton, 13 miles from here, without doing damage.

Twice over 11 years, Wethersfield, 39 miles from Milford, suffered meteorite impacts that punctured the roofs of homes: During 1971, a 12 ounce meteorite lodged in a ceiling; during 1982, a six pound meteorite shattered on a living-room floor. No residents were hurt.

The hit closest to Milford was during 1974 at Stratford, just on the other side of the Housatonic, where a two ounce meteorite the size of two nutmegs bored a hole one inch deep into an asphalt street.

So tiny Connecticut hasn't been spared, but its incoming space rocks likewise have been tiny.