Title: Tagish Lake Meteorite as Messenger of Early Solar System
1Tagish 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
2Fall 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.
3Orbit 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)
4Petrology 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
5Type 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 ??
6Comparison 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
7Which??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 !!
8The 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
9- Solube organics in meteorite products of
aqueous and thermal reaction
Water, HCN, NH3 and 13C- ,15N-, deuterium-rich
interstellar or ganics
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
10Conclusion
Tagish Lake???D-Type ?????????????????????
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