As updates roll in from Russia and the meteorite-related injury toll rises, you may be scrambling to remember what a meteorite really is. If you’re a little rusty on your astronomy, here’s some basic info about space rocks and why this one was unusual.
What is the difference between all these space rocks?
Asteroid: Any number of celestial bodies smaller than a planet that orbit the sun, between a few kilometers and a few hundred kilometers in diameter.
Comet: An icy body that orbits the sun, like an asteroid, that features a “coma,” a thin, temporary atmosphere of gas and dust, and a tail.
Meteor: The glowing streak in the sky we see when an object from space enters the atmosphere and heats up.
Meteoroid: Small rocky or metallic pieces of debris flying through space that can come from a fragment of an asteroid or comet. They can be anywhere from the size of a speck of sand to the size of a large boulder.
Meteorite: The a portion of a meteoroid or asteroid that survives the journey through a planet’s atmosphere to make impact.
Bolide: An especially bright meteor — a fireball that explodes. Geologists use the term when they don’t know the nature of an actual projectile to mean a large impactor that forms a crater.
Special bonus definition: Tektite! Pieces of natural glass that are believed to form when meteorites collide with the Earth, rapidly heating up quartz-rich soil and rock and sending the molten material flying over great distances. When it cools, it forms tektites.
When one of these space rocks has an orbit that swings within 1.3 AUs (about the distance between the Earth and the Sun) of our fair planet, it’s deemed a near-Earth object.
As much as 100,000 tons of space-stuff lands on Earth every year, most of it dust from collisions in the atmosphere, according to geologist Denton Ebel, the American Museum of Natural History’s curator of meteorites. Laurie Leshin, the dean of science at Rensselaer Polytechnic Institute in New York, puts that number at closer to 40,000 tons, but because most cosmic dust collects at the Earth’s poles in ice or is collected by high-flying planes, it’s difficult to get an exact number.
Addi Bischoff, a University of Muenster mineralogist, told the AP that strikes the size of this one happen five to 10 times a year, but not in an area where they would cause injuries. Most of them land in the desert or the ocean and don’t cause much of a ruckus.
“The bigger ones that come in and survive are rarer,” he says. The largest known meteorite to hit the Earth is the Hoba meteorite, a 60-ton hunk of iron discovered in Namibia in 1920. It’s estimated that it fell less than 80,000 years ago.
Source: Popular Science