[meteorite-list] NASA and International Researchers Obtain Crucial Data from Meteoroid Impact (Chelyabinsk)

Wed Nov 6 15:18:25 EST 2013

Amazing that only about 1000 kg or so had been found. But the strewn field is massive, certainly more than 100 miles long and up to 6-8 miles wide at the start. 
Very good read and makes me fondly remember my time hunting at Chelyabinsk.
Michael Farmer

Sent from my iPhone

> On Nov 6, 2013, at 1:10 PM, Ron Baalke <baalke at zagami.jpl.nasa.gov> wrote:
> 
> 
> 
> November 6, 2013
> 
> Dwayne Brown
> Headquarters, Washington      
> 202-358-1726
> dwayne.c.brown at nasa.gov
> 
> Rachel Hoover
> Ames Research Center, Moffett Field, Calif. 
> 650-604-4789
> rachel.hoover at nasa.gov
> 
> Karen Randall
> SETI Institute
> 650 960-4537
> krandall at seti.org
> 
> RELEASE 13-327
> 
> NASA and International Researchers Obtain Crucial Data from Meteoroid Impact
> 
> A team of NASA and international scientists for the first time have gathered 
> a detailed understanding of the effects on Earth from a small asteroid 
> impact. 
> 
> The unprecedented data obtained as the result of the airburst of a meteoroid 
> over the Russian city of Chelyabinsk on Feb. 15, has revolutionized scientists' 
> understanding of this natural phenomenon.
> 
> The Chelyabinsk incident was well observed by citizen cameras and other 
> assets. This factor provided a unique opportunity for researchers to calibrate 
> the event, with implications for the study of near-Earth objects (NEOs) 
> and the development of hazard mitigation strategies for planetary defense. 
> Scientists from nine countries now have established a new benchmark for 
> future asteroid impact modeling. 
> 
> "Our goal was to understand all circumstances that resulted in the shock 
> wave," said meteor expert Peter Jenniskens, co-lead author of a report 
> published in the journal Science.
> 
> Jenniskens, a meteor astronomer at NASA's Ames Research Center and the 
> SETI Institute, participated in a field study led by Olga Popova of the 
> Institute for Dynamics of Geospheres of the Russian Academy of Sciences 
> in Moscow in the weeks following the event.
> 
> "It was important that we followed up with the many citizens who had firsthand 
> accounts of the event and recorded incredible video while the experience 
> was still fresh in their minds," said Popova. 
> 
> By calibrating the video images from the position of the stars in the 
> night sky, Jenniskens and Popova calculated the impact speed of the meteor 
> at 42,500 mph (19 kilometers per second). As the meteor penetrated through 
> the atmosphere, it fragmented into pieces, peaking at 19 miles (30 kilometers) 
> above the surface. At that point the superheated meteor appeared brighter 
> than the sun, even for people 62 miles (100 kilometers) away.
> 
> Because of the extreme heat, many pieces of the meteor vaporized before 
> reaching Earth. Scientists believe that between 9,000 to 13,000 pounds 
> (4,000 to 6,000 kilograms) of meteorites fell to the ground. This amount 
> included one fragment weighing approximately 1,400 pounds (650 kilograms). 
> This fragment wasrecovered from Lake Chebarkul on Oct. 16 by professional 
> divers guided by Ural Federal University researchers in Yekaterinburg, 
> Russia.
> 
> NASA researchers participating in the 59 member consortium study suspect 
> the abundance of shock fractures in the rock contributed its breakup in 
> the upper atmosphere. Meteorites made available by Chelyabinsk State University 
> researchers were analyzed to learn about the origin of the shock veins 
> and their physical properties. Shock veins are caused by asteroid collisions. 
> When asteroid collide with each other, heat generated by the impact causes 
> iron and nickel components of the objects to melt. These melts cool into 
> thin masses, forming metal veins - shock veins - in the objects.
> 
> "One of these meteorites broke along one of these shock veins when we 
> pressed on it during our analysis," said Derek Sears, a meteoriticist 
> at Ames.
> 
> Mike Zolensky, a cosmochemist at NASA's Johnson Space Center in Houston, 
> may have found why these shock veins (or shock fractures), were so frail. 
> They contained layers of small iron grains just inside the vein, which 
> had precipitated out of the glassy material when it cooled.
> 
> "There are cases where impact melt increases a meteorite's mechanical 
> strength, but Chelyabinsk was weakened by it," said Zolensky.
> 
> The impact that created the shock veins may have occurred as long ago 
> as 4.4 billion years. This would have been 115 million years after the 
> formation of the solar system, according to the research team, who found 
> the meteorites had experienced a significant impact event at that time.
> 
> "Events that long ago affected how the Chelyabinsk meteoroid broke up 
> in the atmosphere, influencing the damaging shockwave," said Jenniskens.
> 
> NASA's Near-Earth Object Program sponsors research to better understand 
> the origin and nature of NEOs. These essential studies are needed to inform 
> our approach to preparing for the potential discovery and deflection of 
> an object on a collision course with the Earth.
> 
> NASA's recently announced asteroid initiative includes the first mission 
> to capture and relocate an asteroid, as well as a grand challenge to find 
> and characterize all asteroid threats to human population. It represents 
> an unprecedented technological feat that will lead to new scientific 
> discoveries and technological capabilities that will help protect our 
> home planet.
> 
> Aside from representing a potential threat, the study of asteroids and 
> comets represent a valuable opportunity to learn more about the origins 
> of our solar system, the source of water on the Earth, and even the origin 
> of organic molecules that lead to the development of life.
> 
> For more information about the Chelyabinsk field study visit:
> 
> http://cams.seti.org/index-chelyabinsk.html
> 
> For more information on asteroids and comets, visit:
> 
> http://www.nasa.gov/asteroids
> 
> For more information about NASA, visit:
> 
> http://www.nasa.gov
> 
> -end-
> 
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