A Reduced Organic Carbon Component in Martian Basalts Steele, A.; McCubbin, F. M.; Fries, M. ...
Science (American Association for the Advancement of Science),
07/2012, Letnik:
337, Številka:
6091
Journal Article
Recenzirano
The source and nature of carbon on Mars have been a subject of intense speculation. We report the results of confocal Raman imaging spectroscopy on 11 martian meteorites, spanning about 4.2 billion ...years of martian history. Ten of the meteorites contain abiotic macromolecular carbon (MMC) phases detected in association with small oxide grains included within high-temperature minerals. Polycyclic aromatic hydrocarbons were detected along with MMC phases in Dar al Gani 476. The association of organic carbon within magmatic minerals indicates that martian magmas favored precipitation of reduced carbon species during crystallization. The ubiquitous distribution of abiotic organic carbon in martian igneous rocks is important for understanding the martian carbon cycle and has implications for future missions to detect possible past martian life.
The annual 14C data in tree rings is an outstanding proxy for uncovering extreme solar energetic particle (SEP) events in the past. Signatures of extreme SEP events have been reported in 774/775 CE, ...992/993 CE, and ∼660 BCE. Here, we report another rapid increase of 14C concentration in tree rings from California, Switzerland, and Finland around 5410 BCE. These 14C data series show a significant increase of ∼6‰ in 5411–5410 BCE. The signature of 14C variation is very similar to the confirmed three SEP events and points to an extreme short‐term flux of cosmic ray radiation into the atmosphere. The rapid 14C increase in 5411/5410 BCE rings occurred during a period of high solar activity and 60 years after a grand 14C excursion during 5481–5471 BCE. The similarity of our 14C data to previous events suggests that the origin of the 5410 BCE event is an extreme SEP event.
Plain Language Summary
The 14C data of tree rings register extreme storms of solar energetic particles (SEPs), far larger than the largest SEP event ever observed in the Space Era. So far, three extreme SEP events have been reported as a rapid 14C increase in tree rings and 10Be and 36Cl increases in ice cores. In this study, we found a new rapid 14C increase in 5410 BCE using annual 14C content in ring samples from California, Switzerland, and Finland. The 14C signature of 5410 BCE event ties the origin of this 14C excursion to an extreme SEP event similar to three other extreme SEP events (774/775 CE, 992/993 CE, and ∼660 BCE) confirmed with radionuclides of ice cores.
Key Points
Rapid 14C increase of ∼6‰ with significant level was found in tree rings from California, Switzerland, and Finland around 5410 BCE
Five thousand, four hundred ten BCE event occurred during a period of high solar activity and 60 years after a grand 14C excursion of ∼20‰ from 5481 to 5471 BCE
The similarity of this 14C signature to already known solar events suggests that the origin of this new 5410 BCE event is an extreme SEP
Whatever the cause, it is extraordinary that dozens of genera of large mammals became extinct during the late Quaternary throughout the Western Hemisphere, including 90% of the genera of the ...xenarthran suborder Phyllophaga (sloths). Radiocarbon dates directly on dung, bones, or other tissue of extinct sloths place their "last appearance" datum at ≈11,000 radiocarbon years before present (yr BP) or slightly less in North America, ≈10,500 yr BP in South America, and ≈4,400 yr BP on West Indian islands. This asynchronous situation is not compatible with glacial-interglacial climate change forcing these extinctions, especially given the great elevational, latitudinal, and longitudinal variation of the slothbearing continental sites. Instead, the chronology of last appearance of extinct sloths, whether on continents or islands, more closely tracks the first arrival of people.
To investigate muon-induced nuclear reactions leading to the production of radionuclides, targets made of C
9H
12, SiO
2, Al
2O
3, Al, S, CaCO
3, Fe, Ni, Cu, Gd, Yb and Tl were irradiated with 100 ...and 190 GeV muons in the NA54 experimental setup at CERN. The radionuclide concentrations were measured with accelerator mass spectrometry and γ-spectroscopy. Results are presented for the corresponding partial formation cross-sections. Several of the long-lived and short-lived radionuclides studied are also produced by fast cosmic ray muons in the atmosphere and at depths underground. Because of their importance to earth sciences investigations, calculations of the depth dependence of production rates by fast cosmic ray muons have been made.
ABSTRACT
Today, accelerator mass spectrometry (AMS) technology enables us to carry out very precise measurements of radiocarbon (
14
C). Unfortunately, due to fluctuations in the
14
C calibration ...curve, the resulting calibrated time intervals vary from decades up to centuries in calibrated age. Within a time scale of several decades, we can find several time intervals on the
14
C calibration curve which correspond with periods of rapid increases in atmospheric
14
CO
2
activity. Some of these “high slope” parts of the calibration curve could be used for fine time resolution for radiocarbon dating of individual samples. Nevertheless, there are certain limitations owing to the properties of the samples measured. We have prepared a time-resolution curve for the
14
C dating method, applying calibration curve IntCal13 and assuming an uncertainty of
14
C analyses ±15 yr BP (for recent samples). Our curve of the time resolution covers the last 50 ka. We found several time intervals with time resolution below 50 yr BP for the last 3 ka. Several time intervals which can enable substantially better time resolution compared to neighboring parts of the calibration curve were also found for periods older than 3 ka.
We performed a new series of measurements on samples that were part of early measurements on radiocarbon (14C) dating made in 1948–1949. Our results show generally good agreement to the data ...published in 1949–1951, despite vast changes in technology, with only two exceptions where there was a discrepancy in the original studies. Our new measurements give calibrated ages that overlap with the known ages. We dated several samples at four different laboratories, and so we were also able to make a small intercomparison at the same time. In addition, new measurements on samples from other Egyptian materials used by Libby and co-workers were made at UC Irvine. Samples of tree rings used in the original studies (from Broken Flute Cave and Centennial Stump) were obtained from the University of Arizona Laboratory of Tree-Ring Research archive and remeasured. New data were compared to the original studies and other records.
This article reports on materials excavated and analyzed since 2008 at the multi-component open-air Tolbor-15 Site (Selenge River basin, northern Mongolia). Also discussed are problems of chronology ...and periodization of the Mongolian Upper Paleolithic based on radiocarbon dating, including new determinations available for the Tolbor-4 and 15 sites, along with associated archaeological materials. The early stage of the Early Upper Paleolithic (EUP) in Mongolia persisted for a relatively long period and can be divided into two sub-chrons, the earliest ranging from 40 to 35,000 BP. The later stage of the Mongolian EUP, falling between 33 and 26,000 BP, is represented by assemblages from the Khangai Mountains (e.g., Tolbor-4 and 15, Orkhon-7) and the Gobi Altai district (e.g., Tsagaan Agui Cave, Chikhen Agui Rockshelter, Chikhen-2). The middle Upper Paleolithic in Mongolia has been identified only on the basis of sites in the Orkhon River valley, all of which post-date ca. 25,000 BP. The material culture of this long period is characterized by the complete replacement of blade industries by flake industries, along with the parallel development of the pressure-flaked microblade technique. The later phase of the Mongolian Upper Paleolithic is well-dated down to the end of the Pleistocene. Typical industries include those excavated at Tolbor-15, which are characterized by the predominance of microcores reduced by both pressure and percussion, the appearance of retouched points on flakes, and an increase in the number of microblades as a fraction of overall blade blanks.
Though tree-ring chronologies are annually resolved, their dating has never been independently validated at the global scale. Moreover, it is unknown if atmospheric radiocarbon enrichment events of ...cosmogenic origin leave spatiotemporally consistent fingerprints. Here we measure the
C content in 484 individual tree rings formed in the periods 770-780 and 990-1000 CE. Distinct
C excursions starting in the boreal summer of 774 and the boreal spring of 993 ensure the precise dating of 44 tree-ring records from five continents. We also identify a meridional decline of 11-year mean atmospheric radiocarbon concentrations across both hemispheres. Corroborated by historical eye-witness accounts of red auroras, our results suggest a global exposure to strong solar proton radiation. To improve understanding of the return frequency and intensity of past cosmic events, which is particularly important for assessing the potential threat of space weather on our society, further annually resolved
C measurements are needed.
The annual
C data in tree rings is an outstanding proxy for uncovering extreme solar energetic particle (SEP) events in the past. Signatures of extreme SEP events have been reported in 774/775 CE, ...992/993 CE, and ∼660 BCE. Here, we report another rapid increase of
C concentration in tree rings from California, Switzerland, and Finland around 5410 BCE. These
C data series show a significant increase of ∼6‰ in 5411-5410 BCE. The signature of
C variation is very similar to the confirmed three SEP events and points to an extreme short-term flux of cosmic ray radiation into the atmosphere. The rapid
C increase in 5411/5410 BCE rings occurred during a period of high solar activity and 60 years after a grand
C excursion during 5481-5471 BCE. The similarity of our
C data to previous events suggests that the origin of the 5410 BCE event is an extreme SEP event.
Stepped-heating experiments on martian meteorites Allan Hills 84001 (ALH84001) and Elephant Moraine 79001 (EETA79001) revealed low-temperature (200 to 430 degrees Celsius) fractions with a carbon ...isotopic composition δ $^{13}$C between -22 and -33 per mil and a carbon-14 content that is 40 to 60 percent of that of modern terrestrial carbon, consistent with a terrestrial origin for most of the organic material. Intermediate-temperature (400 to 600 degrees Celsius) carbonate-rich fractions of ALH84001 have δ $^{13}$C of +32 to +40 per mil with a low carbon-14 content, consistent with an extraterrestrial origin, whereas some of the carbonate fraction of EETA79001 is terrestrial. In addition, ALH84001 contains a small preterrestrial carbon component of unknown origin that combusts at intermediate temperatures. This component is likely a residual acid-insoluble carbonate or a more refractory organic phase.
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