[meteorite-list] Chelyabinsk Meteorite Sheds Light on Dinosaur Extinction Mystery

From: lebofsky at lpl.arizona.edu <lebofsky_at_meteoritecentral.com>
Date: Wed, 16 Jul 2014 15:45:49 -0700
Message-ID: <fab72c5929293f506107826f26033307.squirrel_at_webmail.lpl.arizona.edu>

Hi Mike:

That is not what the press release says.

It is still thought that the KT impactor was carbonaceous. There was also
thought, based on being dark and formation age of the BAF (when the parent
body was disrupted), that the BAF was the source of the KT impactor.
However, there is a better spectral match between the Baptistina Asteroid
Family members and the shocked-darkened material seen in the Chelyabinsk
meteorites than there is between these members and carbonaceous
meteorites. This implies that the BAF members are shock-darkened and not
carbonaceous.

Larry

> This is an interesting theory. But, how does Chelyabinsk completely
> rule out a carbonaceous KT impactor? Until we recover an extant
> sample of the KT impactor, the question is still unanswered. Yes,
> there are dark meteorites that are not carbon-rich. But how does this
> fact rule out a carbonaceous (or any) impactor for the KT impact? Am
> I missing something?
>
> Best regards,
>
> MikeG
>
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>
> On 7/16/14, Ron Baalke via Meteorite-list
> <meteorite-list at meteoritecentral.com> wrote:
>>
>>
>> NEWS RELEASE FROM THE PLANETARY SCIENCE INSTITUTE
>>
>> FROM:
>> Alan Fischer
>> Public Information Officer
>> Planetary Science Institute
>> 520-382-0411
>> 520-622-6300
>> fischer at psi.edu
>>
>> Russian Meteorite Sheds Light on Dinosaur Extinction Mystery
>>
>> July 16, 2014, Tucson, Ariz. -- A long-standing debate about the source
>> of
>> the asteroid that impacted the Earth and caused the extinction of the
>> dinosaurs has been put to rest thanks to the Chelyabinsk meteorite that
>> disintegrated over Russia in February 2013, a new paper published in the
>> journal Icarus shows.
>>
>> Astronomers have debated whether the dinosaur killer was linked to the
>> breakup of a large asteroid forming the Baptistina Asteroid Family (BAF)
>> beyond Mars, some of which ended up on Earth-crossing orbits. The
>> asteroid
>> impacting Earth is thought to have been dark and carbonaceous. The BAF
>> hypothesis was bolstered by them being dark and with a spectral shape
>> similar to carbonaceous meteorites.
>>
>> Analysis of the Chelyabinsk meteorite shows that shock produced during
>> catastrophic disruption of a large asteroid can darken otherwise bright
>> silicate material. Shock darkening was first reported by Dan Britt (now
>> at
>> the University of Central Florida) in the early 1990s. The Chelyabinsk
>> meteorite has both bright unshocked and dark shocked material. However,
>> the
>> details of the spectra of the dark Chelyabinsk material closely
>> reproduces
>> spectral signatures seen with members of the Baptistina Asteroid Family,
>> said Planetary Science Institute Research Scientist Vishnu Reddy, lead
>> author of "Chelyabinsk meteorite explains unusual spectral properties
>> of
>> Baptistina Asteroid Family that appears in Icarus.
>>
>> "Shock and impact melt can make bright asteroids dark, Reddy said. "In
>> other words, not all dark asteroids are rich in carbon as once thought."
>> The latest measurements rule out the possibility for the Baptistina
>> family
>> being the source of the K/T impactor, he added.
>>
>> 'The link between the K/T impacator, thought to be carbonaceous, and
>> BAF,
>> has been proved invalid," Reddy said.
>>
>> Chelyabinsk provided a great opportunity to see the mixture of shocked
>> and
>> unshocked material in a single meteorite, Reddy said while cautioning
>> that
>> no clear evidence exists that the Russian meteorite itself came from the
>> Baptistina family.
>>
>> "The new finding has implications for hazards from Near-Earth Objects
>> and
>> for mining asteroids for space-based resources," Reddy said. "A
>> potential
>> target identified as primitive and rich in volatiles/organics and carbon
>> based on its spectral colors could in fact be just shocked material with
>> entirely different composition."
>>
>> PSI researchers David P. O'Brien and Lucille Le Corre were among the
>> co-authors on the paper.
>>
>> This research work was supported by grants from NASA's Planetary Mission
>> Data Analysis Program, NEOO Program and Planetary Geology and Geophysics
>> Program.
>>
>>
>> CONTACT:
>> Vishnu Reddy
>> Senior Scientist
>> 808-342-8932
>> reddy at psi.edu
>>
>> PSI INFORMATION:
>> Mark V. Sykes
>> Director
>> 520-622-6300
>> sykes at psi.edu
>>
>>
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Received on Wed 16 Jul 2014 06:45:49 PM PDT