Last month’s topic for Breakfast with the Birds was Meteors. Bob Dispenza, an Allen County naturalist at Metea Park, was the guest speaker. His talk was filled with interesting facts about meteors and he even brought along three meteorites to show us.
First some definitions: A meteor is a piece of stone, metal, or ice debris from a comet or asteroid which has entered our atmosphere and is burning up. They range from small grains to about a yard wide. A meteorite is a meteor that has struck the earth. And a meteoroid is the same composition, but it’s not in our atmosphere yet, so it’s not glowing. When you see a shooting star—that’s a meteor.
Any night there are likely to be 10-20 meteors visible. During a meteor shower there may be 50-60 an hour, because the earth is passing through the stream of debris that a comet leaves in its wake, rather than just encountering a random bit of space dust. The best visibility is usually just before dawn, not in the evening hours, so instead of staying up late to watch for a meteor, it’s more productive to get up early. This is due to the earth’s rotation and the direction of the impact. I’ve read several sources and listened carefully, but I still don’t think I’m qualified to explain it to you. Check the NASA website (nasa.gov) for a scientific explanation. Meteors enter our atmosphere at speeds ranging from 25,000 mph to 160,000 mph. No wonder they burn up! And most of them do long before there is any chance of impact. When one does hit the earth, it is travelling much more slowly, maybe about 120-130 mph, because the atmosphere has slowed it down. Only one person, a woman from Alabama, is ever known to have been hit by a meteor, and she was indoors at the time, so the structure of the house slowed the meteor even more, and all she got was a large bruise. Actually, about 100 tons of space dust land on earth each day!
Meteorites are usually alloys of iron and nickel. There are three major types of meteorites: iron, stony and iron-stony. Iron meteorites are very heavy, magnetic, and are almost completely metal. Stony-iron meteorites are composed of nearly equal amounts of metal and silicate minerals, and are considered the most beautiful of meteorites. Stony meteorites are mostly silicate minerals and are the most common meteorites found. They often contain chondrules, which are spherical inclusions of silicate minerals formed at extremely high temperatures. No earth rocks contain chondrules. Bob passed around one of each type of meteorite. We have touched a piece of outer space!
A recent meteorite can sometimes be distinguished from an earth rock by its fusion crust, which is a thin dark gray or black layer on the exterior of the meteorite caused by the intense heat of its journey through our atmosphere. Older meteorites may have this crust eroded and so be harder to identify without a chemical analysis.
Antarctica is the best place for hunting meteorites, even though meteors fall evenly around the globe. Most end up falling into the ocean. But the ones that hit Antarctica fall onto ice and so are less damaged than falling onto rocks. Then they tend to stand out more in the ice. And finally the flow of the ice pushes them together and brings them to the surface, so they are found in larger concentrations.
You can’t see meteors during the day because the sunlight obscures them. They are best viewed on a clear, moonless night, away from city lights, security lights, etc. But you can hear them during the day! Tune in an AM radio station that is very far away and quite buzzy. Occasionally it will get clearer for a few moments. That clarity is caused because the radio waves are bouncing off the ionized air trailing behind a meteor. The clarity may only last a second, but it could be longer depending on the size of the meteor. Pretty cool little fact!
Our best known meteor crater is in Arizona, but we have one also in Indiana, near Kentland. The Kentland crater is about 8 miles in diameter. Part of it was covered by the glaciers, and since it happened millions of years ago, it isn’t readily visible to the untrained eye.
An interesting theory is that the pressure of the impact of a meteor may be what was responsible for coal being transformed into the diamonds found in South Africa.
Last week there was supposed to be a major meteor shower that for most of us just didn’t happen. A few people reported seeing meteors, but it wasn’t the big show scientists had hoped for. There are meteor showers that occur on a regular schedule and often the LaGrange County Parks Department has a park open late at night for viewing. Watch the newspaper for announcements just before August 12 for the Perseids meteor shower and November 16 for the Leonids.
As you can see, Breakfast with the Birds is not just about birds. It covers any and all natural phenomena with a different topic each month. If you’re free on the third Wednesday of the month at 8:30 a.m. come out to Maple Wood, enjoy a donut and coffee, and learn about Mother Nature. June 18 is the next session, entitled “Luna.” Join us to learn about the moon