Bitterroot Gem & Mineral Club

Bitterroot Gem & Mineral Club of Montana

Bolides & Impact-Craters, & their Debris (Meteorites & Tektites) By Wayne Farley

Bolide: (Wikipedia, Ref-1) A bolide (French via Latin from the Greek βολίς bolís, "missile"[2][3]) is an extremely bright meteor, especially one that explodes in the atmosphere. In astronomy, it refers to a fireball about as bright as the full moon, and it is generally considered a synonym of a fireball. In geology, a bolide is a very large impactor. One definition describes a bolide as a fireball reaching an apparent magnitude of −14 or brighter; more   than twice as bright as the full moon. Another definition describes a bolide as any generic large crater-forming impacting body whose composition (for example, whether it is a rocky   or metallic asteroid, or an icy comet) is unknown. 


A super-bolide is a bolide that reaches an apparent magnitude of −17 or brighter. Recent examples of superbolides include: 1. the 04/22/12 Sutter’s Mill meteor which occurred over California and 2. the 02/15/13 Chelyabinsk meteor, which occurred over Russia.  The Sutter's Mill meteorite is a carbonaceous chondrite which entered the Earth's atmosphere and broke up at about 07:51 Pacific time on April 22, 2012.[6][7] The name comes from the Sutter's Mill, the California Gold Rush site, near which some pieces were recovered. This was the largest meteoroid impact over land since asteroid 2008 TC3. Meteor astronomer Peter Jenniskens assigned SM numbers to each meteorite, with the documented find location preserving information about where a given meteorite was located in the impacting meteoroid. As of May 2014, 79 fragments have been publicly documented with a find location. The largest (SM53) weighs 205 grams, and the second largest (SM50) weighs 42 grams. The meteorite was found to contain some of the oldest material in the solar system. Two 10-micron diamond grains (xenoliths) were found in the meteorite recovered before the rain fell. In primitive meteorites like Sutter's Mill, some grains survived from what existed in the cloud of gas, dust and ice that formed the solar system. 


The Chelyabinsk meteor was a superbolide caused by an approximately 20-metre near-Earth asteroid that entered Earth's atmosphere over Russia on 15 February 2013 at about 09:20 YEKT (03:20 UTC), with a speed of 19.16 ± 0.15 kilometres per second (60,000[–69,000 km/h or 40,000–42,900 mph). It quickly became a brilliant superbolide meteor over the southern Ural region. The light from the meteor was brighter than the Sun, visible up to 100 km (62 mi) away. It was observed over a wide area of the region and in neighbouring republics. 


Some eyewitnesses also felt intense heat from the fireball. Due to its high velocity and shallow angle of atmospheric entry, the object exploded in an air burst over Chelyabinsk Oblast, at a height of around 29.7 km (18.5 mi; 97,000 ft). The explosion generated a bright flash, producing a hot cloud of dust and gas that penetrated to 26.2 km (16.3 mi), and many surviving small fragmentary meteorites, as well as a large shock wave. The bulk of the object's energy was absorbed by the atmosphere, with a total kinetic energy before atmospheric impact estimated from infrasound and seismic measurements to be equivalent to the blast yield of a nuclear weapon in the 400–500 kiloton (about 1.4–1.8 PJ) range – 26 to 33 times as much energy as that released from the atomic bomb detonated at Hiroshima. The object was undetected before its atmospheric entry, in part because its radiant was close to the Sun. Its explosion created panic among local residents, and about 1,500 people were injured seriously enough to seek medical treatment. All of the injuries were due to indirect effects rather than the meteor itself, mainly from broken glass from windows that were blown in when the shock wave arrived, minutes after the superbolide's flash. Some 7,200 buildings in six cities across the region were damaged by the explosion's shock wave, and authorities scrambled to help repair the structures in sub-freezing temperatures. With an estimated initial mass of about 12,000–13,000 metric tons (13,000–14,000 short tons, heavier than the Eiffel Tower), and measuring about 20 metres in diameter, it is the largest known natural object to have entered Earth's atmosphere since the 1908 Tunguska event, which destroyed a wide, remote, forested, and very sparsely populated area of Siberia. The Chelyabinsk meteor is also the only meteor confirmed to have resulted in a large number of injuries. No deaths were reported.  


This Research will be Continued next month!