An anonymous reader writes: In what is one of the largest asteroid chunks ever found on Earth, an excavation team from a local astronomy club this week excavated a thirty ton iron-nickel meteorite from the ground.
Dubbed Gancedo after a nearby town, it isn't a record-holder, but it sure is big. What I found interesting from the article, however, is this:
Gancedo's fall to Earth occurred between 4,000 and 6,000 years ago. Locals knew of the fall for centuries, even making iron tools from meteorites found in the strewnfield. In the 16th century, the Spanish became interested in stories of a piece of iron that fell from the sky, and in 1774 don BartolomÃ© Francsico de Maguna led an expedition that came across a mass of iron, referred to as MesÃn de Fierro ("Table of Iron" in Spanish). Another 1,400-pound fragment from Campo del Cielo named Otumpa now resides at the British Museum in London. With more than 100 tons of meteorite recovered, Campo del Cielo is the top producer in terms of pure meteorite mass worldwide.
The Campo del Cielo strewnfield extends over an ellipse 3 km wide by 19 km long over an area northwest of Buenos Aires, and meteorites found here have a polycrystalline coarse octahedrite composition characteristic of iron-nickel meteorites. They are also unusually pure even among iron-nickel meteorites, consisting of 93% iron. Most of the remaining 7% is nickel, and less than 1% are trace elements.
The evidence here is that a very dense asteroid, weighing a minimum of 100 tons but probably several times that, smashed into the Earth about five thousand years ago. Yet, all life on Earth was not wiped out, as is repeatedly suggested might happen whenever a similarly sized asteroid zips close past the Earth. In fact, there is no evidence this impact had any significant global environmental effects.
Remember this the next time another asteroid of similar size zips past the Earth and the media doom-sayers begin to sing their siren song again.