[meteorite-list] One of the best of the 2008 TC3 articles

From: lebofsky at lpl.arizona.edu <lebofsky_at_meteoritecentral.com>
Date: Wed, 25 Mar 2009 16:24:10 -0700 (MST)
Message-ID: <48d43600570aefbb3f2451efafd2dd92.squirrel_at_webmail1.lpl.arizona.edu>

Hi everone:

As someone who has studied asteroids, this is great news.

Only two comments:

1. I am a little concerned with the classification of the "asteroid" as F.
The spectral range is not perfect and I wonder what the uncertainty of the
spectrum is (might be very poor quality at the longer wavelengths).

2. I do not think that 2008 TC 3 was "dusty." It was tumbling in space and
spinning once ever 50 to 100 seconds. An object this size is not going to
have a dusty surface!

my two cents

Larry

> Okay, this needs to go on that list from a few days ago of "most important
> meteorites."
>
> http://www.livescience.com/space/090325-asteroid-meteorites.html
>
>
> Space 'Rosetta Stone' Unlike Anything Seen Before
>
> By Andrea Thompson, Senior Writer
>
> posted: 25 March 2009 02:00 pm ET
>
> Meteorite fragments of the first asteroid ever spotted in space before it
> slammed into Earth's atmosphere last year were recovered by scientists
> from the
> deserts of Sudan.
>
> These precious pieces of space rock, described in a study detailed in the
> March
> 26 issue of the journal Nature, could be an important key to classifying
> meteorites and asteroids and determining exactly how they formed.
>
> The asteroid was detected by the automated Catalina Sky Survey telescope
> at
> Mount Lemmon , Ariz., on Oct. 6, 2008. Just 19 hours after it was spotted,
> it
> collided with Earth's atmosphere and exploded 23 miles (37 kilometers)
> above the
> Nubian Desert of northern Sudan.
>
> Because it exploded so high over Earth's surface, no chunks of it were
> expected
> to have made it to the ground. Witnesses in Sudan described seeing a
> fireball,
> which ended abruptly.
>
> But Peter Jenniskens, a meteor astronomer with the SETI Institute's Carl
> Sagan
> Center, thought it would be possible to find some fragments of the bolide.
> Along
> with Muawia Shaddad of the University of Khartoum and students and staff,
> Jenniskens followed the asteroid's approach trajectory and found 47
> meteorites
> strewn across an 18-mile (29-km) stretch of the Nubian Desert.
>
> "This was an extraordinary opportunity, for the first time, to bring into
> the
> lab actual pieces of an asteroid we had seen in space," Jenniskens said.
>
> Classification
>
> Astronomers were able to detect the sunlight reflected off the car-sized
> asteroid (much smaller than the one thought to have wiped out the
> dinosaurs)
> while it was still hurtling through space. Looking at the signature of
> light, or
> spectra of space rocks is the only way scientists have had of dividing
> asteroids
> into broad categories based on the limited information the technique gives
> on
> composition.
>
> However, layers of dust stuck to the surfaces of the asteroids can scatter
> light
> in unpredictable ways and may not show what type of rock lies underneath.
> This
> can also make it difficult to match up asteroids with meteorites found on
> Earth
> ? that's why this new discovery comes in so handy.
>
> Both the asteroid, dubbed 2008 TC3, and its meteoric fragments indicate
> that it
> could belong to the so-called F-class asteroids.
>
> "F-class asteroids were long a mystery," said SETI planetary
> spectroscopist
> Janice Bishop. "Astronomers have measured their unique spectral properties
> with
> telescopes, but prior to 2008 TC3 there was no corresponding meteorite
> class, no
> rocks we could look at in the lab."
>
> Cooked carbon
>
> The chemical makeup of the meteorite fragments, collectively known as
> "Almahata
> Sitta," shows that they belong to a rare class of meteorites called
> ureilites,
> which may all have come from the same original parent body. Though what
> that
> parent body was, scientists do not know.
>
> "The recovered meteorites were unlike anything in our meteorite
> collections up
> to that point," Jenniskens said.
>
> The meteorites are made of very dark, porous material that is highly
> fragile
> (which explains why the bolide exploded so high up in the atmosphere).
>
> The carbon content of the meteorites shows that at some point in the past,
> they
> were subjected to very high temperatures.
>
> "Without a doubt, of all the meteorites that we've ever studied, the
> carbon in
> this one has been cooked to the greatest extent," said study team member
> Andrew
> Steele of the Carnegie Institution in Washington, D.C. "Very cooked,
> graphite-like carbon is the main constituent of the carbon in this
> meteorite."
>
> Steele also found nanodiamonds in the meteorite, which could provide clues
> as to
> whether heating was caused by impacts to the parent asteroid or by some
> other
> process.
>
> Rosetta Stone
>
> Having spectral and laboratory information on the meteorites and their
> parent
> asteroid will help scientists better identify ureilite asteroids still
> circling
> in space.
>
> "2008 TC3 could serve as a Rosetta Stone, providing us with essential
> clues to
> the processes that built Earth and its planetary siblings," said study
> team
> member Rocco Mancinelli, also of SETI.
>
> One known asteroid with a similar spectrum, the 2.6-km wide 1998 KU2, has
> already been identified as a possible source for the smaller asteroid 2008
> TC3
> that impacted Earth.
>
> With efforts such as the Pan-STARRS project sweeping the skies in search
> of
> other near-Earth asteroids, Jenniskens expects that more events like 2008
> TC3
> will happen.
>
> "I look forward to getting the next call from the next person to spot one
> of
> these," he said. "I would love to travel to the impact area in time to see
> the
> fireball in the sky, study its breakup and recover the pieces. If it's big
> enough, we may well find other fragile materials not yet in our meteorite
> collections."
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Received on Wed 25 Mar 2009 07:24:10 PM PDT