Title: Ancient Artifacts to Martian Meteorites: Radiocarbon Dating with a Particle Accelerator
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3Ancient Artifacts to Martian Meteorites
Radiocarbon Dating with a Particle Accelerator
4Production cartoon
5libby counter
6magnetic mass separation
MASS SEPARATION
7Pioneering studies in AMS
- Nelson, D.E., Korteling, R.G., and Stott, W.R.
1977. Science 198, 507-508. - Bennett, C.L., Beukins, R.P., Clover, M.R.,
Elmore, D., Gove, H.E., Kilius, L., Litherland,
A.E., Purser, K., and Sondheim, W.E. 1977.
Science 198, 508-510. -
- Muller, R.A. 1977. Science 196, 489-494.
8Accelerator Mass Spectrometer (AMS)
914C sample processing wood, charcoal, textiles,
carbonates, bone, etc.
- PRETREATMENT HCl - NaOH - HCl - water
- COMBUSTION cleaned sample O2 (900oC) ? CO2
- GRAPHITIZATION CO2 Zn ? CO ZnO
-
- CO ? C (graphite) on iron powder
- graphite ? instrument
10Accelerator Mass Spectrometer (AMS)
1114C age calculation
12Total Error
For a modern sample, ?statistics 0.002 So,
?total 0.0036 (29 years)
13Sample background
1414C age limits
15NSF-Arizona AMS
1614C age calculation
17Tree ring calibration
- Dendrochronologists have accumulated a continuous
record of tree rings of known age back to about
12,500 years before present. - These include pine and oak trees from North
America and Europe, among others. - Radiocarbon ages of wood from tree rings of known
age have been replicated from a number of
laboratories around the world with high
precision. - ?(Age) ? 0.2 or ?16 years
- Plots of true age (from tree rings) vs.
radiocarbon age allow one to calibrate
radiocarbon ages.
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19Calendar Years from Tree Ring Counting
Wiggle-matching band patterns From many trees to
yield a Composite chronology
1 Year
Early Wood
Late Wood
20Tree ring calib
21AMS samples pie chart
22AAR vs AMS
23Clovis/color
24SierraVista
25METEORITES
- Stony meteorites _at_ 50 oxygen by weight
- As meteorites travel through space they are
bombarded by galactic cosmic rays, producing
radiocarbon 16O p(high energy) ? 14C 3p - Travel times of meteorites through space are 106
to 108 years and equilibrium 14C concentrations
are achieved. - Upon landing on earth, meteorites are shielded
from cosmic radiation by the earths atmosphere
and the 14C content of the meteorite decays with
a half-life of 5730 yrs. - By comparing the 14C content of a fallen
meteorite with the known saturated activity in
space, the time since it landed can be deduced.
26Martian meteorite
27ALH 84001
28U-Th text
29saturated activity
30Collecting speleothems
31speleothem
32Speleothem calibration
33U/Th dated corals
U/Th dated stalagmites Layer counted sediments
Tree Rings
34Shroud of Turin
35SHROUD OF TURIN
- First displayed in Lirey, France in the 1350s.
- Later passed into the hands of the Dukes of Savoy
and then to the Catholic Church. - Brought to Turin in 1578 and placed in the Royal
Chapel of Turin Cathedral in 1694. - In 1988 samples were taken from the Shroud for
AMS 14C dating.
36Shroud sample
37Shroud results
38Shroud calibration and nature
39scroll
40nefertiti
41Duck decoy
42Vinland Map
43Results of Arizona studies of the Vinland Map
- Radiocarbon age
- 46727 radiocarbon yrs BP
- Calibrated age range
- 1423-1445 AD (1 sigma, 68.3 confidence)
- 1411-1468 AD (2 sigma, 95.4 confidence)
44Raphael
45Post bomb curve
46Miami museum
47Cosmogenic isotopes
- ISOTOPE half-life (yrs)
- 14C 5730
- 36Cl 3.0 x 105
- 26Al 7.2 x 105
- 10Be 1.6 x 106
- 129I 1.6 x 107
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50Lab in action photo
51Stopping power vs Energy
52dE/dx detector
53Proportional counter for 14C measurement
- The counter is filled with gas (CO2 or C2H2).
Wait for 14C nuclei to decay and detect
electrons. One of the sample will decay in 80
years. - Modern samples give about 15 dpm g-1C. For a 1
(80 yrs) measurement you need 10,000 counts (11
hours).
14C ? 14N e-
anode
54Dating studies
- Skelton et al (1965) linked the map to the
Council of Basle (1431-1449AD). - McCrone (1974) reported this must be a forgery
due to the presence of anatase (titanium
dioxide). - Cahill et al. (1987) showed the anatase present
at only trace levels. - Donahue et al. (2002) reported that although the
parchment appears to be coated with a recent
material, the cleaned parchment gave a medieval
age.
55Uranium- Thorium dating
56Cutting the samples
57Shroud calibration
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59Rubber ball
60cosmogenic radioisotopes
611948 - 1952
- F. Ajzenberg-Selove
- Stanley Bashkin
- Ray Benenson
- Corny Browne
- Don Craig
- Doug Donahue
- Ross Douglas
- Aaron Galonsky
- Gerson Goldhaber
Truman Hunter Herb Jackson Virgil Johnson Keith
Jones Richard Laubenstein Mollie Jean
Laubenstein Marc McEllistrem Bob Williamson
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