A trove of Chelyabinsk meteorites collected or purchased by Arizona meteorite hunter Michael Farmer. Many are rounded as their outer skins were melted during flight through the atmosphere. Credit: Michael Farmer
It’s official. February’s Russian fireball finally has a birth certificate with a name. The Meteoritical Society, the organization responsible for naming and maintaining the official tally of meteorite finds and falls, has named it Chelyabinsk (pronounced chel-YAH-binsk) after the largest city in the region of the fall.
Meteorite hunter Evgenij Suhanov smiles as he holds a fresh specimen found in the countryside near Chelyabinsk. Credit: Evgenij Suhanov
According to the rules of the Society’s Nomenclature Committee, acceptable names for meteorites include terrain-based features like rivers, mountains, lakes, bays, capes, and islands; political features such as towns, counties, states, and provinces, and sites of human activity such as parks, mines, historical sites and railroad stations. Sites connected to recent human activity like buildings, shops and businesses, schools, bridges, roads, and golf courses are generally not acceptable. Sorry, there won’t be a Target meteorite anytime soon.
A beautiful Chelyabinsk “button” showing flight orientation. The left photo shows the nosecone side that sped downward through the atmosphere. The back side has a melted, frothy texture. Credit: Evgenij Suhanov
Official names are required to publish studies about this or that meteorite in some scientific journals. A meteorite gets a name after it’s been analyzed and classified in the lab. Until that time it’s one of a multitude of “unclassified” meteorites with no official status.
95.6% of meteorites found or seen to fall like Chelyabinsk are classed as ordinary chondrites, rocks containing rounded mineral grains called chondrules and peppered with flakes of metallic iron-nickel. Chondrites (KON-drites) derive from the outer crust of their parent asteroids and get a free trip to Earth after being blasted loose from long-ago impacts by other asteroids.
Ordinary chondrites are further subdivided into H, L and LL varieties. H stands for high metal (12-21% iron-nickel metal in the rock), L for low metal (5-10%) and LL (about 2%).
Chondrules and iron-nickel metal grains on a sawn face of an unnamed chondrite from northern Chile. It’s probably an H5 – high metal and altered minerals from heating. Credit: Randy Korotov
Rocks that ultimately came to Earth as meteorites were heated to varying degrees by the decay of radioactive elements in the asteroid’s crust altering their mineral structure. Those least affected by heat and which most resemble the first solid materials to form in the solar system are petrographic type 3; those most affected are type 6. So for example, an L3 meteorite has low metal and was little affected by heating, while an H6 has lots of metal and got baked.
A cut-open Chelyabinsk specimen shows a light texture with darker patches of shocked or impact-melted minerals. When meteorite minerals like olivine are shocked by impact, chemical changes occur that make them darken. Credit: Evgenij Suhanov
I apologize for the “tech talk” but it will help us better understand the nature of the Russian meteorite. Chelyabinsk is classified as an LL5 chondrite – low metal and a good amount of mineral alteration from early heating. Further, about a third of the stones found consist of a dark impact melt containing mineral and chondrule fragments. Like the name suggests, the melted rock probably came from the impact that sent chunks of the original asteroid on their earthward course.
You might wonder how long it took for the Chelyabinsk meteoroid (the name given a meteor or meteorite before it enters Earth’s atmosphere). Called its cosmic ray exposure age, the average time for an LL5 chondrite to arrive after getting blown off its asteroid is around 31 million years. That is a long, long time yet only a fraction – about 0.7% – of the meteorite’s true age of 4.6 billion years. Kind of makes you stop and reflect, doesn’t it?
Early samples from the perimeter of the hole in the ice of Lake Chebarkul. Credit: AP / The Urals Federal University Press Service, Alexander Khlopotov
I’ve been checking Chelyabinsk meteorites for sale on eBay and the few private sales I’ve been aware of. Prices range from around $35-150 per gram. As of March 21 there are 115 meteorites advertised on eBay as Chelyabinsk by everyone from first-time sellers to well-established meteorite folks. Surprisingly, most of the specimens appear to be the real thing. Chelyabinsk meteorites have either black or brown fusion crust – the dark, melted outer crust from heating during atmospheric entry - smooth or bumpy surfaces and are generally small. Undoubtedly the force of the explosion when the meteorite came down shattered the original meteoroid to bits.
Another fine fusion-crusted Chelyabinsk meteorite, this one weighing 43 grams. Credit: Evgenij Suhanov
Only a few larger pieces have been recovered. The largest weighs about 4 lbs. (1.8 kg). The total amount of material collected by locals and scientists is at least 220 lbs (100 kg) and perhaps more than 1,100 lbs. (500 kg). As for that 26 foot (8 m) hole in the ice in Lake Chebarkul likely punched out by a falling space rock, divers have yet to retrieve the culprit. They did however just discover a 10-foot (3 m) underwater crater offset about 32 feet from the hole.
For more details on the Chelyabinsk meteorite, click HERE.