Sunday, November 27, 2011

Sky Bullets


The word meteor comes from the classical Greek meteoron, which means "atmospheric event", and technically, this modern term refers merely to the streak of photons trailing a meteoroid. A meteoroid, in turn, is any interplanetary object bigger than a speck of dust and smaller than an asteroid.

The atmosphere is something of an Ellis Island stopover. Once it hits Earth, a meteoroid undergoes a scientific immigration process to become a "meteorite".

I particularly like "Aurora Particles" and "Fireballs"

The strewnfield is the area where meteorites from a single fall are dispersed. There are two ways strewnfields can form:
Mid-Air Fragmentation
happens when a large meteoroid enters the atmosphere and explodes due to thermal shock, sending pieces of material over a wide area.
Impact fragmentation is exactly how it sounds, usually creating a circular crater and spreading debris in a smaller, concentrated area.

About 4 billion meteoroids hit Earth every single day; that's about a hundred tons per day of meteor dust. However, most are so tiny as to be harmless, even though they travel at hundreds of kilometers per second.

Photo of Arizona Meteor Crater I took from an airplane!
(Click for closeup)

The largest meteorite known to hit Earth has never been moved from where it fell in Africa. Weighing 60 tons and landing about 80,000 years ago, the "Hoba West" has been declared a national monument by the government of Namibia.

To protect it it from the estimated 100,000 meteoroids that will hit it during it's 20-year life span, the International Space Station is covered with Kevlar ... about a foot thick! This same material is used to manufacture bullet-proof vests.

Perseid Meteor Shower

Meteor showers are named after the constellations they appear to be falling from.

In Sylacauga, Alabama in 1954, a woman named Ann E. Hodges was napping in her home when an 8-pound meteorite smashed through her roof, bounced off a radio and struck her in the arm and hip. This was the first recorded meteoroid to hit a human being on Earth.

If you happen to find a fallen meteorite, the Meteoritical Society demands that you donate 20% or 20 grams (whichever is smaller) for research, but it's all right to sell the rest... unless you live in South Africa, where meteorites are protected under National Heritage Law and must be surrendered whole to authorities.