Professor Wasserburg and his colleagues in the "Lunatic Asylum"
are carrying forward a vigorous research program in several areas. These
range from theoretical studies to the development and application of analytical
methods to the study of some natural systems. The research areas of interest
are in cosmochemistry, geochemistry and aqueous geochemistry. The general
purpose of the cosmochemical research is: 1) to understand the nucleosynthetic
and chemical processes which led to the formation of dust grains around
presolar stars; 2) to model early nucleosynthesis in galaxies; 3) to establish
the chronology of events and processes which led to the formation of the
solar system from the interstellar medium, using short and intermediate
lifetime radioactive nuclides; 4) to understand the events during the
early stages of solar system formation and the development and early evolution
of planets. The geochemical studies are directed toward 1) the structure
and evolution of large scale reservoirs within the earth and their relationship
to major geodynamical processes and 2) the short term processes involving
climate change, recent volcanism and fluid-rock interactions. The fluid
rock interactions are particularly important with regard to environmental
problems and the stability and storage of radioactive waste. Many of these
geochemical studies directly involve field work.
The research involves both students and research faculty in experimental
and theoretical work. A wide variety of advanced instrumentation and
actively used laboratory facilities provide the basis for the studies.
A key to all of this research is the effort toward innovation, invention,
and discovery. The laboratory has had the good fortune to be successful
in identifying and developing new approaches which permit a new look
at old problems and the start of new studies. The diverse areas of study
by Prof. Wasserburg and his colleagues may be seen in the recent, selected
papers listed below.
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J. H. Chen, D. A. Papanastassiou and G. J. Wasserburg
Re-Os systematics in chondrites and the fractionation of the Platinum
Group Elements. Geochim. Cosmochim. Acta 62, 3379-3382 (1998).
B-G. Choi, G. R. Huss and G. J. Wasserburg
Presolar corundum and spinel in ordinary chondrites: Origins from AGB
stars and a supernova. Science 282, 1284-1289 (1998).
M. Busso, R. Gallino and G. J. Wasserburg
Nucleosynthesis in AGB stars: relevance for galactic enrichment and
solar system formation.
Annual Reviews of Astronomy and Astrophys. 37, 239-309 (1999).
B.-G. Choi, G. R. Huss, and G. J. Wasserburg
Circumstellar hibonite and corundum and nucleosynthesis in asymptotic
giant branch stars. Astrophys. J. 522, L133-136 (1999).
H. C. Connolly, Jr., G. R. Huss, and G. J. Wasserburg
On the formation of Fe-Ni metal in CR2 meteorites. Geochim. Cosmochim.
Acta, submitted (2000)
W. Hsu, G. J. Wasserburg, and G. R. Huss
High time resolution by use of the 26Al chronometer in the multistage
formation of a CAI. Earth Planet. Sci. Lett 182, 15-29, (2000).
Y.-Z. Qian and G. J. Wasserburg
Evolution of O abundance relative to Fe.
Astrophys. J., in press (March, 2001).
G. Srinivasan, G. R. Huss, and G. J. Wasserburg
A petrographic, chemical, and isotopic study of Ca-Al-Inclusions and
Al-rich chondrules from the Axtell (CV3) chondrite. Meteoritics and
Planetary Science 35, 1333-1354 (2000).
G. J. Wasserburg and Y.-Z. Qian
A model of metallicity in the evolution of the early universe.
Astrophys. J. 538, L99-L102 (2000).
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A. Kaufman, G. J. Wasserburg, D. Porcelli, M. Bar-Matthews, A. Ayalon,
L. Halicz
U-Th isotope systematics and U-series ages of speleothems from Soreq
Cave, Israel and climatic correlations. Earth Planet. Sci. Lett. 156,
141-155 (1998).
M. Roy-Barman, G. J. Wasserburg, D. A. Papanastassiou and M. Chaussidon
Osmium isotopic compositions and Re-Os concentrations in sulfide globules
from basaltic glasses. Earth Planet. Sci. Lett. 154, 331-347 (1998)
M. Bar-Matthews, A. Ayalon, A. Kaufman, G. J. Wasserburg, B. Ghaleb
Eastern Mediterranean paleoclimate during the last 60,000 years as derived
from speleothems, Soreq Cave, Israel. Earth Planet. Sci. Lett. 166,
85-95 (1999).
M. Sharma, G. J. Wasserburg, A. W. Hofmann, and G. J. Chakrapani
Himalayan uplift and osmium isotopes in oceans and rivers. Geochim.
Cosmochim. Acta 63 , 4005-4012 (1999).
M. Sharma, G. J. Wasserburg, A. W. Hoffman, and D. A. Butterfield
Osmium isotopes in hydrothermal fluids from the Juan de Fuca Ridge.
Earth Planet. Sci. Lett. 179, 139-152 (2000)
P. S. Andersson, D. Porcelli, O. Gustafsson, J. Ingri, and G. J. Wasserburg
The behaviour of uranium isotopes in the low salinity zone of a stable
estuary. Geochim. Cosmochim. Acta, in press (2000).
A. Tricca, D. Porcelli and G. J. Wasserburg
The transport of U- and Th-series nuclides in a sandy unconfined aquifer.
Geochim. Cosmochim. Acta, in press (2001).
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Figure 1: Schematic showing basic components of the transport
model developed by Tricca et al, (2000) for water/rock interaction for
the U-Th series. This model treats flow, adsorption, solution, weathering,
radioactive decay and recoil in an aquifer. It is applied to a ground
water system where data on a wide variety of elements and radionuclides
were studied.
Figure 2: Measured enrichments of 234U
relative to the equilibrium value versus the activity of 238U
in the water. A curve (full) shows results of the theoretical model
for vadose zone input. Note that in this aquifer (Brookhaven, Long Island)
almost all samples simply appear to reflect the vadose zone input and
subsurface interactions are small. (Tricca et al, 2001)
Figure 3: SEM image of the first circumstellar hibonite
S-H5323 (CaAl12O19)
found in a meteorite (Choi et al, 1998). This contains large excesses
of 17O and a depletion of 18O.
The grain had both 26Al and 41Ca
when formed around an Asymptotic Giant Branch star prior to the formation
of the solar system (see figure 4). Only three pre-solar hibonites have
been found. The most recent one by research fellow Natalia Krestina
on January 26, 2001.
Figure 4: Phase diagram showing stability fields of major
oxides in a circumstellar envelope. The principal oxides condensing
first are Al2O3,
hibonite, then spinel. Only two presolar circumstellar spinel grains
have been found so far.
Figure 5: Oxygen isotopic composition of circumstellar
oxide grains recovered from meteorites. The curves show the evolution
of oxygen isotopes as a function of stellar mass for different initial
oxygen values. Note that 18O is destroyed
and 17O is produced in Asymptotic Giant
Branch stars. Note position of hibonite S-H 5323 relative to normal
stellar evolution of a 1.8 solar mass star of solar (Z = 0.02) composition.
Figure 6: Histogram showing the rate of turn on of galaxies
at red shifts from ~2.0 to 2.4 based on the Fe abundances observed by
Prochaska and Wolfe (2000) in damped Lyman a
galaxies as modelled by Wasserburg and Qian (2000). The time is in units
of 109 years after Big Bang. Note the
slow rate of turning on the lightbulbs.
Figure 7: Cartoon showing injection of material from different
stellar sources into a sequence of molecular clouds. The parent cloud
of the protosun contains gas and preserved dust grains from several
generations of stars formed in different molecular clouds, as well as
that added to the local inventory by "local" sources. All
of these diverse stellar sources provide nuclei with short-, intermediate-,
and long-lifetime nuclei. Each is produced over different time scales.
Figure 8: First determination of Os in hydrothermal vent
fluids (Sharma et al, 2000). Inverse of 188Os
versus 187Os/188Os
diagram showing that one sample (Monolith, 1991) plots on the mixing
line between seawater and a component with 187Os/188Os
= 0.11. All other samples define a nearly horizontal array that can
be attributed to nearly quantitative precipitation of Os during the
ascent and cooling of the hydrothermal fluids.
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