Top Thirty Publications |
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The
following list are papers that I am most proud of, either because they
represent pieces of work I think have proved of long term value, or I
consider them particularly original, or because they were just fun to
research or write. Electronic
copies are available by clicking on the publication number.
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Number
in Publication List |
Publication
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My reasons for
including paper in list
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Sears, D.W. and
Mills, A.A. (1973) Temperature
gradients and atmospheric ablation rates for the Barwell meteorite. Nature
Physical Science, 242, 25-26. |
The first publication, and Alan showed me
how. A neat application of
quantitative theory to something normally considered purely
descriptively. I am not sure
anyone cared, but 30 years later I was thinking about Earth Return Vehicles
for sample return missions and this paper was of great value to me. |
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Sears. D.W. and
Axon, H.J. (1976) Nickel and
cobalt contents of chondritic meteorites. Nature, 260, 34-35. |
I was trying to find something to do with
magnetic residues from my PhD work and identified a new parameter to explore
chondrite meteorites that has been used by many groups, the Co content of the
kamacite. |
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Sears, D.W. (1980) Thermoluminescence of meteorites;
relationships with their K-Ar age and their shock and reheating history. Icarus, 44, 190-206. |
Some Russian researchers had previously
argued that since K-Ar age correlated with TL sensitivity, TL was created by
radiation damage. I showed that,
in fact, this was not the case but the high TL sensitivity of crystalline
rocks was being lowered by shock, which also caused a loss of Ar. I like this paper because it is well
done and comes to an unexpected but very solid conclusion. |
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Sears, D.W., Grossman, J.N., Melcher,
C.L., Ross, L.M. and Mills, A.A. (1980)
Measuring the metamorphic history of unequilibrated ordinary
chondrites. Nature, 287,
791-795. |
This is my first well-known and well-cited
paper, establishing a sequence and a classification scheme for primitive
meteorites that is still in common use after nearly 30 years. John Wasson played a crucial role,
encouraging us to make the measurements and providing the samples. |
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Guimon, R.K., Weeks, K.S., Keck, B.D. and
Sears, D.W.G. (1984)
Thermoluminescence as a palaeothermometer. Nature, 311, 363-365. |
A novel and largely unanticipated result,
that the shape of the TL glow curve also reflects thermal history, not just
the level of induced TL. This
paper reminds me of the importance of enthusiastic graduate students who are
not deterred from making measurements that some said could not be done. I learned a lot from Kyle, who died
in early 2006. |
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Hartmetz, C.P., Ostertag, R. and Sears,
D.W.G. (1986) A
thermoluminescence study of experimentally shock-loaded oligoclase and
bytownite. Proc. 17th Lunar and Planet. Sci. Conf., Part 1, J. Geophys.
Res., 91, E263-E274. |
Work on terrestrial minerals sometimes
helps us understand extraterrestrial materials. This work showed that the shape of the TL glow curve is
related to the degree of disorder in the feldspar crystals and thus explains
why the shape of the TL glow curve can be related to thermal history. |
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Hasan, F.A., Haq, M. and Sears, D.W.G.
(1987) Natural
thermoluminescence levels in meteorites, I: 23 meteorites of known Al-26 content. Proc. 17th Lunar and Planet. Sci.
Conf., Part 2, J. Geophys. Res., 92, E703-E709. |
This paper was fun because it was done at
the instigation of a committee trying to increase the utility of Antarctic
meteorites. Sure enough, we
found that natural TL could identify meteorites that were petrographically
familiar but had interesting physical histories. As a result of this paper,
NASA and NSF established the natural TL Survey of Antarctic meteorites. Robert Walker and Steve Sutton played
an important advocacy role in this effort. |
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Batchelor, J.D. and Sears, D.W.G.
(1991) Metamorphism of eucrite
meteorites studied quantitatively using thermoluminescence. Nature 349,
516-519. |
We showed that the TL technique worked not
just with primitive chondrites but also with these meteorites that were
formed as lavas during some sort of volcanism. |
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Benoit, P.H., Sears, D.W.G. and McKeever,
S.W.S. (1991) The natural
thermoluminescence of meteorites - II. Meteorite orbits and orbital
evolution. Icarus 94, 311-325. |
Early work by physicists suggested that
natural TL levels would reflect perihelion distance, and we pursued this
idea, successfully. |
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Benoit P.H. and Sears D.W.G. (1992) The
breakup of a meteorite parent body and the delivery of meteorites to
Earth. Science 255,
1685-1687. |
The boldness of this work pleases me. Meteorites that were all part of an
asteroid that fragmented by a single event 8 Ma ago - but arrived on earth
40,000 years apart - have different metamorphic history. Orbital streaming means that
meteorites that released from different places on the asteroid arrive on
Earth at different times. We
made it into the New York Times! |
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Benoit P.H., Jull A.J.T., Mckeever S.W.S.
and Sears D.W.G. (1993) The
natural thermoluminescence of meteorites VI: Carbon-14, thermoluminescence and the terrestrial ages of
meteorites. Meteoritics 28,
196-203. |
This paper pleases me because it is one
big "I told you so"!
When our natural TL data were first published, people cynical of TL
pointed out their poor agreement with 14C data. Twenty years later radiocarbon data
improved because of the invention of accelerator mass spectrometry and the
correlation was vastly improved. |
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Benoit P.H., Sears D.W.G. and McKeever
S.W.S. (1993) Natural
thermoluminescence and terrestrial ages of meteorites from a variety of temperature
regimes. Radiat. Detect.
Dosimet. 47, 699-674. |
This was a hurriedly-written but never-the-less
very nice paper showing how natural TL can be used in a variety of climates
to determine terrestrial age, adjusting the theoretical curves for local
temperatures. |
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Matsunami S., Ninagawa K., Nishimura S.,
Kubon N., Yamamoto I., Kohata M., Wada T., Yamashita Y., Lu Jie, Sears D. W.
G., and Nishimura H. (1993)
Thermoluminescence and compositional zoning in the mesostasis of a
Semarkona group A1 chondrules and new insights into the chondrule-forming
process. Geochim. Cosmochim.
Acta 57, 2101-2110. |
Here we tackled a dogma of 20 years - that
chondrules were closed systems during their formation - with unique new
observations and careful reasoning.
We were successful in overturning the dogma. |
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Sears D.W.G., Benoit P.H. and Lu Jie
(1993) Two groups each with
distinctive rims in Murchison recognized by cathodoluminescence. Meteoritics 28,
669-675. |
A new type of observation
(cathodo-luminescence) showed rather clearly that the famous rims on
chondrules depended on what was being rimmed, and therefore that rims are
condensates from evaporation that occurred during chondrule formation. |
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Benoit P.H. and Sears D.W.G. (1994) A recent meteorite fall in Antarctic
with an unusual orbital history.
Earth Planet. Sci. Lett. 120, 463-471. |
A technique has come of age when it makes
discoveries that were not predicted.
While we were looking at terrestrial ages and searching for meteorites
that had been close to the Sun, we discovered a meteorite that had only
recently - in geological terms - become Earth-crossing. |
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Sears D.W.G., Huang S. and Benoit P.H.
(1995) Chondrule formation,
metamorphism, brecciation, an important new primary chond-rule group, and the
classification of chondrules. Earth
Planet. Sci. Lett. 131, 27-39. |
Two groups of chondrules (lithic and
droplet) have been known for a century under various names, neither with
“chondritic” phase compositions.
We found a third type, which have chondritic compositions while being
essentially unequilibrated. |
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Sears D.W.G., Symes S.P., Guimon R.K. and
Benoit P.H. (1995) Chemical and
physical studies of type 3 chondrites XII: The metamorphic history of CV chondrites and their components. Meteoritics 30, 707-714. |
We even found that the refractory
inclusions in Allende - famous for being the oldest materials in the solar
system - also form a metamorphic sequence that can be identified from their
induced TL properties. |
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Yanghong Zhang, Benoit P.H. and Sears
D.W.G. (1995) The classification
and thermal history of enstatite chondrites. Jour. Geophys. Res. - Planets 100,
9417-9438. |
Ms. Zhang was my guide on a visit to China
and I was fascinated by her. She
later came to the US as my student and did some neat work in the enstatite
chondrites. Here we stressed the
major differences in thermal history of the EL and EH classes which were
previsouly thought be a single genetic series.. |
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Huang Shaoxiong and Sears D. W. G.
(1996) Metal-silicate
fractionation in the surface dust layers of accreting planetesimals: Implications for the formation of
chondrites and the nature of asteroid surfaces. J. Geophys. Res. - Planets 101, 29,373 -
29,385. |
A brave new suggestion that the chondrite
classes - marked for their differing amounts of metal relative to silicates -
were caused by the way metal and silicate became separated on the surface of
an asteroid. |
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Sears D.W.G., Huang S. and Benoit P.H.
(1996) Open-system behavior
during chondrule formation. In
"Chondrules and the Protoplanetary Disk", (eds. Hewins, R.,
Jones R. H. and Scott E. R. D.), pp. 221-231. Cambridge University Press. |
This was my major paper establishing the
open system nature of chondrule formation - which has implications for
explaining the meteorite classes - and since this paper was published the
conclusion has hardly been challenged. |
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Yanghong Zhang, Benoit P.H. and Sears
D.W.G. (1996) Pyroxene
structures, cathodoluminescence and the thermal history of the enstatite
chondrites. Meteorit. Planet.
Sci. 31, 87-96. |
Here we pursued an idea briefly mentioned
in the literature previously that the structure of pyroxenes determines their
cathodoluminescence properties, and this was a reflection of differences
between the classes in thermal history. |
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Akridge D. G. and Sears D. W. G.
(1998) Regolith and megaregolith
formation of H-chondrites:
Thermal constraints on the parent body. Icarus 132, 185-195. |
Glen performed these thermal calculations
that showed that chondrite meteorites could all come from the surface layers
of an asteroid. |
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Sears D. W. G. (1998) The rarity of chondrules and CAI
in the early solar system and
some astrophysical consequences.
Astrophys. Jour. 498, 773-778 |
Another attempt to tackle dogmas, and I
think it was at least partially successful - why assume chondrules are common
because they are common in a major class of the fallen meteorites. All the evidence is that they are
actually rare, as rare as refractory inclusions called CAI. |
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Sears D. W. G. and Kral T. A. (1998) Martian "microfossils" in
lunar meteorites? Meteorit.
Planet. Sci. 33, 791-794. |
Sometimes politics overwhelms science,
such as when some JSC researchers found "fossils" in a martian
meteorite. The JSC-NASA-media
circus over this issue involved sex, violence, power, and money – I am
waiting for the movie – in which our small paper was a plea for sanity. Nonsense, we said, there are similar
structures in meteorites from barren planets. A lot of people agreed with us, but said nothing, waiting
for the dollars. |
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Symes S. J. K., Sears D. W. G., Taunton
A., Akridge D. G., Yanghong Zhang and Benoit P. H. (1998) The crystalline lunar spherules: Their formation and implications for
the origin of meteoritic chondrules.
Meteorit. Planet. Sci. 33, 13-29. |
I was surprised to learn that this is one
of my most cited papers. It
makes the case that chondrules - whose origin has long been unclear - are
simply the impact melt spherules from the surfaces of asteroids. This was a very controversial
conclusion, but has met with a surprisingly positive response. |
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Akridge D. G. and Sears D. W. G.
(1999) The gravitational and
aerodynamic sorting of meteoritic chondrules and metal: Experimental results with
implications for chondritic meteorites.
J. Geophys. Res. (Planets) 104, 11853-11864. |
A very sound and very original attempt to
understand chondritic meteorites in terms of processes likely to be occurring
on the surface of an asteroid |
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Sears D. W. G., Kochan H. and Huebner W.
F. (1999) Simulation experiments
and surface processes on comets.
Meteorit. Planet. Sci. 34, 497-525. |
My first excursion into comets and
laboratory space simulations and brought me into contact with two new friends,
Walter Huebner and Herman Kochan |
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Sears, D. W. G.; Allen, C. C.; Britt, D.
T.; Brownlee, D. E.; Cheng, A. F.; Chapman, C. R.; Clark, B. C.; Drake, B.
G.; Fevig, R. A.; Franchi, I. A.; Fujiwara, A.; Gorevan, S. P.; Kochan, H.;
Lewis, J. S.; Lindstrom, M. M.; Nishiizumi, K.; Race, M. S.; Scheeres, D. J.;
Scott, E. R. D.; Taylor, G. J.; Yano, H. (2002) Near-Earth Asteroid Sample Return. In The Future of Solar System
Exploration (2003-2013) -- Community Contributions to the NRC Solar System
Exploration Decadal Survey. ASP Conference Proceedings, Vol. 272. Edited
by Mark V. Sykes. San Francisco, Astronomical Society of the Pacific, 2002,
pp. 111-140. |
An important step in my efforts to
persuade the scientific community and NASA that we will never be able to
fully understand primitive materials of the solar system without bringing
back samples from known locations on a known asteroid. This article was
apparently successful because near-Earth asteroid sample return featured
prominently in the final National Academies report. |
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Akridge, D. G.; Akridge, J. M. C.;
Batchelor, J. D.; Benoit, P. H.; Brewer, J.; DeHart, J. M.; Keck, B. D.; Jie,
Lu; Meier, A.; Penrose, M.; Schneider, D. M.; Sears, D. W. G.; Symes, S. J.
K.; Yanhong, Zhang (2004)
Photomosaics of the cathodoluminescence of 60 sections of meteorites
and lunar samples. Journal of
Geophysical Research, Volume 109, Issue E7, CiteID E07S0 |
Summarizes the work of virtually all my
students to that date and represents a unique and widely unappreciated view
of meteorites, the view from cathodoluminescence which captures both
petrologic and compositional information |
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Sears, Derek W. G.; Moore, Shauntae R.
(2005) On laboratory simulation
and the evaporation rate of water on Mars. Geophysical Research Letters, Volume 32, Issue 16,
CiteID L16202 |
An entirely new research area for us. Groups at Caltech and Berkeley tried
to make these measurements, but our results are by far the best for precision
and accuracy. The paper is a
testimony to an incredible student. |
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Sears, Derek W. G.; Chittenden, Julie D.
(2005) On laboratory simulation
and the temperature dependence of the evaporation rate of brine on Mars. Geophysical Research Letters,
Volume 32, Issue 23, CiteID L23203 |
And we could do the measurements at any
temperature. So what if the data
simply confirmed theory, it is a weak theory it shows we have mastered the
techniques. While very different
to Shauntae, Julie is also an incredible student. |
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