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

From: Michael Farmer <mike_at_meteoritecentral.com>
Date: Wed, 6 Nov 2013 13:18:25 -0700
Message-ID: <88D59EE4-BA6B-4AFB-B504-27E0881E8794_at_meteoriteguy.com>

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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Received on Wed 06 Nov 2013 03:18:25 PM PST