Meteorites on the Road

Synopsis of the June 12, 2009, lecture by Dick Pugh, field scientist at Cascadia Meteorite Laboratory

by Evelyn Pratt with edits by Melinda Hutson

Portland State University is proud of having the only meteorite lab in the Pacific Northwest. The Cascadia Meteorite Laboratory was established in 2003 as part of the Department of Geology. In 2005 it became an official repository for type specimens of newly-classified meteorites. The laboratory is run by Melinda Hutson, Alec Ruzicka, and Dick Pugh. It now has slightly under 500 meteorites.

What is the difference between an asteroid, a meteoroid, a meteor, and a meteorite? If it is in space and you can see it with a telescope, it’s called an asteroid; if it is in space and you cannot see it with a telescope, it's called a meteoroid. A meteoroid may be traveling at 25,000 mph when it hits the atmosphere 90 miles high. Once a meteoroid enters the Earth's atmosphere, its exterior becomes hot enough to glow and it is called a meteor or a fireball. By 50 miles above Earth, most meteors break up into pieces. A desk-size meteoroid entering the atmosphere has the power of 50 tons of TNT. If a piece of the meteor hits the ground and can be picked up, then it’s called a meteorite.

Mr. Pugh showed many examples of meteorites. On February 19, 2008, Providence Hospital photos showed a fireball 250 miles away that traveled from the Canadian Border to La Grande. It landed somewhere in the Blue Mts. at 5:31 a.m.

In October 1992, the town of Peekskill, N.Y., was hit by 70 fragments of an incoming meteoroid, from basketball to marble size. One meteorite hit an old car that had been for sale for $300, transforming it into a car worth $10,000.

On Aug. 10, 1972, a daytime photo showed an object estimated at 9 to 50 feet in diameter that skipped in and out of the atmosphere, about 37 miles up. Fortunately that large of a meteoroid didn't land.

The meteor crater that we are most familiar with, Barringer Meteor Crater in Arizona, formed when a nickel-iron meteor hit 25,000 to 50,000 years ago. The resulting crater is about ¾ mile in diameter, and almost 600 feet deep. Most meteorites come from the asteroid belt. Jupiter is close enough that every now and then its gravity forces a meteoroid out of orbit. Meteorites tend to be heavier than Earth rocks, are often attracted to magnets, and irregularly shaped. Also, most have "thumbprint" pits and are covered with a thin black or brownish fusion coating. If they've been around a while, the coating may be rusty. They often contain native iron-nickel.

There are many different kinds of meteorites, including multiple groups made entirely or mostly of rock (stony meteorites), some made of a mixture of rock and metal (stony-irons), and some made almost entirely or iron-nickel alloy (irons). Only 6% of all meteorites are irons, but these are the easiest to find.

One percent of meteorites are stony-irons. There are two types. One is a pallasite, where olivine crystals float in a matrix of nickel-iron. The other is a mesosiderite, which is a mixture of half metal and half rock.

Ninety-three percent of all meteorites that fall are stony meteorites, including chondrites and achondrites. There is an average of one on every square mile of earth. Chondrites are by far the most common, and contain olivine-pyroxene and iron sulfide. Often they are filled with rounded bits called chondrules that look like frozen tapioca pudding. The fusion coating on these meteorites is rarely thicker than a fingernail. A few rare stony meteorites aren't chondrites, and are called achondrites (meaning not a chondrite). These include rocks from the asteroids, our Moon, and Mars. Some of these are distinguished by having an unusual waxy/shiny fusion crust.

Cutting, polishing, and etching an iron meteorite reveals what is called a Widmanstatten pattern, which looks like cross-sections of many triangular crystals. In order for this texture to be large enough to be visible to the naked eye, this meteorite must have cooled very slowly, about 3 degrees every million years. Cutting these nickel-iron-cobalt-steel objects is not easy.

Graphite is not uncommon in meteorites, and it can be metamorphosed into diamonds. A common myth is that meteorites start fires when they land--they don't. In space, a meteoroid is cold. Only a very thin layer is heated during the few seconds that the meteor is incandescent. At about 20 miles up, friction has slowed the meteor down enough that its exterior is no longer hot enough to glow. By the time a meteorite hits the ground, it is somewhere between slightly warm to very cold. People have seen frost forming on a freshly fallen meteorite.

At 8 or 9 feet by 5 feet, the largest known single-piece meteorite on the Earth's surface is the Hoba meteorite in Namibia. It weighs over 60 tons.

Man's first use of meteorites was for weapons and tools. 1500 years ago, long before the Industrial Age, the sword Excaliber must have been stainless steel from a meteorite.

One of the best "scientific instruments" to find meteorites with is a plow. Kansas is flat and plowed; it also lacks dark rocks, so it is a good place to find meteorites easily. Meteorites are harder to locate in Oregon, where black basalt and black meteorites have enough iron in them so both rust.

Many meteors tumble as they come through the atmosphere, but some don't, coming in with one side facing forward the whole time. These meteorites become cone shaped. This fusion-crusted cone is often criss-crossed with cooling fractures.

Carbonaceous chondrites are rare. They are high in carbon, and also may contain water, amino acids, and ketones. They are 4.6 billion years old, and some may have originated in comets.

The meteorites from our Moon contain a lot of different rock types, including basalt, anorthite, and peridotite rocks blasted out from the lunar mantle. Martian meteorites are basalts or peridotites. In 1996, researchers at the Johnson Space Center claimed to have found possible evidence for Martian microbes in these meteorites. This launched a heated debate, and most scientists now find the evidence unconvincing.

Only four meteorites have ever been found in Oregon. One was found in Sam's Valley, north of Medford, Oregon, in 1894; since then, a few more pieces of this iron meteorite have been recovered.

The most famous is the 15.5 ton Willamette Meteorite, found in West Linn in 1902. A local farmer took 3 months to move it from Oregon Iron and Steel land ¾ mile to his own land. The heavily-loaded wagon left easily-followed tracks. Oregon Iron and Steel men followed them, then lost a lawsuit attempting to get the meteorite back. People started trying to take off souvenir pieces of it. Next it was barged to Portland and exhibited in the 1905 World's Fair here. An Eastern lady bought it for $26,000 and gave it to the Natural History Museum in New York City, where it reposes today. It was probably a glacial erratic, brought down on a really big iceberg during a Missoula flood.

The Klamath Falls iron meteorite was found in 1952 in southern Oregon.

In May of 1981 a chondrite hit a house at 1:05 in the morning in Salem. The Salem meteorite is the only one of the four Oregon meteorites that is not an iron meteorite. It is not surprising that the Salem is a chondrite, as most observed meteorite falls are of chondrites.