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

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Wed, 16 Jul 2014 14:31:17 -0700 (PDT)
Message-ID: <201407162131.s6GLVHL7003227_at_zagami.jpl.nasa.gov>

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
Received on Wed 16 Jul 2014 05:31:17 PM PDT