More than 100 tons of space debris enters the Earth’s atmosphere every day, mostly in the form of dust and tiny rocks that burn up during entry. Occasionally a larger object may strike the atmosphere and produce a fireball as it burns up, but these events rarely cause any significant damage. Very rarely, however, one of these astronomical events can have lasting, and even catastrophic, effects.
TERMINOLOGY
In astronomical terms, a single piece of rock floating through the solar system can bear many names. A large piece of rock moving through space is called an asteroid, and if that asteroid breaks up, the smaller pieces may be called meteoroids. If an asteroid or meteoroid enters the Earth’s atmosphere, it becomes a meteor, and if any fragment of the meteor survives entry and reaches the ground, it is a meteorite.
K-PG EXTINCTION EVENT
At the end of the Cretaceous Period, approximately 65 million years ago, an enormous extinction event wiped out 70 percent of the species on Earth, including the dinosaurs. Geologists discovered large amounts of the rare mineral iridium in strata from this period, suggesting that the cause of the extinction was a massive asteroid impact in the Yucatan Peninsula of Mexico. While the facts of the event are still in question, the amount and distribution of iridium found suggests that the source was an asteroid approximately 10 kilometers across. The Cretaceous-Paleogene Extinction Event -- formerly known as the Cretaceous-Tertiary Extinction Event -- is one of the factors that made mammals the dominant land-based form of life on the planet.
TUNGUSKA
On June 30, 1908, an explosion occurred above Tunguska in central Russia with a force equivalent to 185 times that of the nuclear bomb that devastated Hiroshima. The site of the location would not be explored for another 19 years, due to the harsh conditions and poor survival equipment of the time, but resultant study of the blast site since then indicates that the culprit was an asteroid that entered the Earth’s atmosphere and exploded. According to NASA’s estimates, the object was 120 feet (36 meters) across, traveling at 33,500 miles per hour (53,900 kph) when it broke up.
CHELYABINSK
On February 15, 2013, a massive explosion in the sky rocked Chelyabinsk in southwestern Russia. The blast was powerful enough to shatter windows throughout the area, injuring more than 1,000 residents, and several cameras recorded the event in detail. NASA estimates that the meteor that caused the 500-kiloton blast was 55 feet (17 meters) across, and had a mass of approximately 10,000 tons. Coincidentally, another asteroid passed close to Earth the same day, 2012 DA14, although studies of the objects’ trajectories suggest no link between the two events.
SYLACAUGA
An asteroid event does not always need to be large to be notable. On November 30, 1954, a meteor the size of a softball fell near Sylacauga, Alabama. This particular rock struck the home of Ann Hodges, passing through her roof, bouncing off a radio, and striking her where she lay napping on a sofa. The impact left a sizable bruise on her hip, and marked her as the first known human victim of a meteorite strike. Hodges retained ownership of the meteorite, later donating it to the Alabama Museum of Natural History.