Tagish Lake Meteorite as Messenger of Early Solar System

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Tagish Lake MeteoriteasMessenger of Early Solar
System

• The Tagish Lake Meteorite A Possible Sample from
  a D-Type Asteroid, T. Hiroi et al. (2001)
• SCIENCE, vol293, 2234-2236
• The Organic Content of the Tagish Lake Meteorite,
  S. Pizzarello et al. (2001)
• SCIENCE, vol293, 2236-2239

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Fall and Recovery
18 January 2000 at 1643 UT Yukon and Northwest
territories
P. G. Brown et al. (2000) Science vol 290
Ewald Lemke (63-year-old realtor) caught on Film
at 845 a.m.
First 25 to 26 January 2000 total 0.85 kg
From the surface of frozen lake frozen
fragments !!
Second Between 20 April and 8 May 2000 410
meteorite fragments !!! immersion in meltwater.
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Orbit and Composition
New Type of Carbonaceous Chondrite Most primitive
meteorite group C2 less altered (aqueously
altered on parent asteroid)
typical Apollo asteroid-type orbit (Earth
crossing)
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Petrology of Tagish Lake Meteorite

• Carbonate-poor lithology
• Carbonate-rich lithology

• Phyllosilicate-rich clasts, coarse- to
  fine-grained
• Chondrules, aqueously-altered
• Other constituents include anhydrous forsteritic
  olivine grains (mainly Fo99)
• Lithic fragments
• Calcium-Aluminum-rich inclusion (CAI)
• Magnetite
• Pyrrhotite
• Cr-Ni phosphide
• Chromite
• Spinel-rich spherules and other inclusions
• Matrix saponite, serpentine with Fe-Ni sulfides

• very fine-grained phyllosilicates of mostly
  saponite with rare clasts or magnetite
• Fe-Mg-Ca-Mn carbonates occur, but calcium
  carbonate is rare

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Type of Asteroidbased onAlbedo and Refractance
Spectra

• C-type, includes more than 75 of known
  asteroids extremely dark (albedo 0.03) similar
  to carbonaceous chondrite meteorites
  approximately the same chemical composition as
  the Sun minus hydrogen, helium and other
  volatiles
• Have some classes C-, D-, G-, B-, F-, T-, P-Type
• S-type, 17 relatively bright (albedo .10-.22)
  metallic nickel-iron mixed with iron- and
  magnesium-silicates
• M-type, most of the rest bright (albedo
  .10-.18) pure nickel-iron

Tagish Lake Meteorite P or D-Type ??
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Comparison of reflectance spectra
Reflectance Eight-Color Asteroid Survey (ECAS)
and 52-Color Asteroid Survey
Albedo Infrared Astronomical Satellite (IRAS)
Redness R(853)/R(550) Brightness albedo
measured by the IRAS
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Which??Parent Asteroid

• D-Type asteroid located outer part of asteroid
  belt
• D asteroid 368?, 336?, 773?
• Kirkwood gaps chaotic zone

Orbital periods of simple fraction times
Jupiters period
Deep Impact !!
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The main features of organics

• The dominance of water-soluble carboxyl and
  dicarboxyl compounds
• Relatively low in amino acids
• The aromatic character of insoluble carbon

Tagish Lake meteorite is as Unique in organic
chemistry
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• Solube organics in meteorite products of
  aqueous and thermal reaction

Water, HCN, NH3 and 13C- ,15N-, deuterium-rich
interstellar or ganics

• In Tagish Lake suite

Murchison amio and hydroxy acids no clear example
of such chemistry
Calboxylic acids and n-alkanes catalytic surface
processes rather than the random combination
radicals
But, organic content consistent with an origin
from a primitive body that had accreted solar
nebular and interstellar material
Heterogeneity of Carbonaceous Chondrite
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Conclusion
Tagish Lake???D-Type ?????????????????????
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