Skip to Content

Found 39,370 Resources

Scientists Are Hacking Tomatoes To Make Them Keep Growing All Night Long

Smithsonian Magazine

The wonders of industrial agriculture have already given us the little red jewel that is the modern hot house tomato. They might look nice, but these plump, spongy fruits, bred to hold up in the truck, are tasteless. Now, scientists have a new trick in store for the tomato. They are working on a way to circumvent the tomato's natural need for rest and prodding tomato plants towards a full 24-hour growth cycle of staggering productivity.

Tomatoes, like most plants and animals, follow a circadian rhythm, a biological inner clock that tells them when to sleep and when to grow. But sleeping time is wasted time—so far as growers looking to maximize plant productivity are concerned—and, as Caleb Garling writes for Modern Farmer, geneticists have been hard at work trying to hack tomatoes into giving up their nap time.

According to new research, says Garling, geneticists have pinpointed a gene from wild tomatoes that deals how the plants handle light and have selectively bred it into modern hybrid tomatoes. This one little tweak caused a big jump in tomato productivity. The change, say the researchers in their study, “results in up to 20% yield increase, showing that limitations for crop productivity, caused by the adaptation of plants to the terrestrial 24-h day/night cycle, can be overcome.”

Differentiating successful and failed molluscan invaders in estuarine ecosystems

Smithsonian Libraries
Despite mounting evidence of invasive species' impacts on the environment and society, our ability to predict invasion establishment, spread, and impact are inadequate. Efforts to explain and predict invasion outcomes have been limited primarily to terrestrial and freshwater ecosystems. Invasions are also common in coastal marine ecosystems, yet to date predictive marine invasion models are absent. Here we present a model based on biological attributes associated with invasion success (establishment) of marine molluscs that compares successful and failed invasions from a group of 93 species introduced to San Francisco Bay (SFB) in association with commercial oyster transfers from eastern North America (ca. 1869 to 1940). A multiple logistic regression model correctly classified 83% of successful and 80% of failed invaders according to their source region abundance at the time of oyster transfers, tolerance of low salinity, and developmental mode. We tested the generality of the SFB invasion model by applying it to 3 coastal locations (2 in North America and 1 in Europe) that received oyster transfers from the same source and during the same time as SFB. The model correctly predicted 100, 75, and 86% of successful invaders in these locations, indicating that abundance, environmental tolerance (ability to withstand low salinity), and developmental mode not only explain patterns of invasion success in SFB, but more importantly, predict invasion success in geographically disparate marine ecosystems. Finally, we demonstrate that the proportion of marine molluscs that succeeded in the latter stages of invasion (i.e. that establish self-sustaining populations, spread and become pests) is much greater than has been previously predicted or shown for other animals and plants.

Climate and vegetational regime shifts in the late Paleozoic ice age earth

Smithsonian Libraries
The late Paleozoic earth experienced alternation between glacial and non-glacial climates at multiple temporal scales, accompanied by atmospheric CO2 fluctuations and global warming intervals, often attended by significant vegetational changes in equatorial latitudes of Pangaea. We assess the nature of climate2013vegetation interaction during two time intervals: middle2013late Pennsylvanian transition and Pennsylvanian2013Permian transition, each marked by tropical warming and drying. In case study 1, there is a catastrophic intra-biomic reorganization of dominance and diversity in wetland, evergreen vegetation growing under humid climates. This represents a threshold-type change, possibly a regime shift to an alternative stable state. Case study 2 is an inter-biome dominance change in western and central Pangaea from humid wetland and seasonally dry to semi-arid vegetation. Shifts between these vegetation types had been occurring in Euramerican portions of the equatorial region throughout the late middle and late Pennsylvanian, the drier vegetation reaching persistent dominance by Early Permian. The oscillatory transition between humid and seasonally dry vegetation appears to demonstrate a threshold-like behavior but probably not repeated transitions between alternative stable states. Rather, changes in dominance in lowland equatorial regions were driven by long-term, repetitive climatic oscillations, occurring with increasing intensity, within overall shift to seasonal dryness through time. In neither case study are there clear biotic or abiotic warning signs of looming changes in vegetational composition or geographic distribution, nor is it clear that there are specific, absolute values or rates of environmental change in temperature, rainfall distribution and amount, or atmospheric composition, approach to which might indicate proximity to a terrestrial biotic-change threshold.

No post-Cretaceous ecosystem depression in European forests? Rich insect-feeding damage on diverse middle Palaeocene plants, Menat, France

Smithsonian Libraries
Insect herbivores are considered vulnerable to extinctions of their plant hosts. Previous studies of insect-damaged fossil leaves in the US Western Interior showed major plant and insect herbivore extinction at the Cretaceous–Palaeogene (K–T) boundary. Further, the regional plant–insect system remained depressed or ecologically unbalanced throughout the Palaeocene. Whereas Cretaceous floras had high plant and insect-feeding diversity, all Palaeocene assemblages to date had low richness of plants, insect feeding or both. Here, we use leaf fossils from the middle Palaeocene Menat site, France, which has the oldest well-preserved leaf assemblage from the Palaeocene of Europe, to test the generality of the observed Palaeocene US pattern. Surprisingly, Menat combines high floral diversity with high insect activity, making it the first observation of a ‘healthy’ Palaeocene plant–insect system. Furthermore, rich and abundant leaf mines across plant species indicate well-developed host specialization. The diversity and complexity of plant–insect interactions at Menat suggest that the net effects of the K–T extinction were less at this greater distance from the Chicxulub, Mexico, impact site. Along with the available data from other regions, our results show that the end-Cretaceous event did not cause a uniform, long-lasting depression of global terrestrial ecosystems. Rather, it gave rise to varying regional patterns of ecological collapse and recovery that appear to have been strongly influenced by distance from the Chicxulub structure.

Ecological divergence and medial cuneiform morphology in gorillas

Smithsonian Libraries
Gorillas are more closely related to each other than to any other extant primate and are all terrestrial knuckle-walkers, but taxa differ along a gradient of dietary strategies and the frequency of arboreality in their behavioral repertoire. In this study, we test the hypothesis that medial cuneiform morphology falls on a morphocline in gorillas that tracks function related to hallucial abduction ability and relative frequency of arboreality. This morphocline predicts that western gorillas, being the most arboreal, should display a medial cuneiform anatomy that reflects the greatest hallucial abduction ability, followed by grauer gorillas, and then by mountain gorillas. Using a three-dimensional methodology to measure angles between articular surfaces, relative articular and nonarticular areas, and the curvatures of the hallucial articular surface, the functional predictions are partially confirmed in separating western gorillas from both eastern gorillas. Western gorillas are characterized by a more medially oriented, proportionately larger, and more mediolaterally curved hallucial facet than are eastern gorillas. These characteristics follow the predictions for a more prehensile hallux in western gorillas relative to a more stable, plantigrade hallux in eastern gorillas. The characteristics that distinguish eastern gorilla taxa from one another appear unrelated to hallucial abduction ability or frequency of arboreality. In total, this reexamination of medial cuneiform morphology suggests differentiation between eastern and western gorillas due to a longstanding ecological divergence and more recent and possibly non-adaptive differences between eastern taxa. Published by Elsevier Ltd.

Geomorphic Evolution of the Martian Highlands Through Ancient Fluvial Processes

Smithsonian Libraries
Craters in the Martian highlands are preserved in various stages of degradation. As a result of an erosional process active from the Middle Noachian (4.40?3.92 b.y.) through the Hesperian (3.55?1.8 b.y.), ejecta associated with fresh impact craters became etched, hummocky, and dissected by runoff channels. With time, interior gullies became deeply incised and ejecta deposits were entirely removed. Infilling of the craters followed until, in some instances, the craters were completely buried. Only fluvial processes explain these morphologic variations, the size range of affected craters, and the size-frequency distribution curves associated with these crater populations. Based on the number of superposed fresh impact craters, fluvial processes affecting the highlands ceased entirely by the end of the Hesperian. No correlation between cessation of degradation and latitude exists. However, a strong correlation exists between cessation of degradation and elevation. Degradation ended at higher elevations (e.g., 3?4 km; N [5]=?200, Late Noachian) before lower elevations (e.g., 1?2 km; N[5]=?180, Early Hesperian), suggesting that cessation was coupled to desiccation of the volatile reservoir and degassing of a 5?20 bar primordial atmosphere. Volatiles released to the surface by runoff channel formation and seepage may have been part of a complex hydrologic cycle that included periodic, heavy amounts of precipitation. Rainfall was principally responsible for degrading the highlands, eroding impact craters, and redistributing sediments. Rainfall also recharged the highland aquifers, allowing sapping and seepage to continue for hundreds of millions of years. As the primordial atmosphere was lost, cloud condensation, and thus rainfall and aquifer recharge, occurred at progressively lower elevations. Based on estimates on the amount of material removed and duration of degradation, denudation rates averaged 0.0001?0.005 mm/yr. These rates are equivalent to those in terrestrial periglacial environments.

Lava flow surface roughness and depolarized radar scattering

Smithsonian Libraries
Surface roughness has a strong controlling influence on radar scattering and other types of remote sensing observations. We compare field measurements of surface topography and dielectric constant for a range of lava flow textures to aircraft multipolarization radar observations at 5.7, 24, and 68 cm (C, L, and P band) wavelengths. The roughness is found to vary with scale in a self-affine (fractal) manner for scale lengths between 25 cm (the smallest horizontal step size) and 3-5 m. This result is used to demonstrate that a two-component surface description, consisting of the fractal dimension and rms height or slope at some reference scale, can resolve some of the ambiguities in previous efforts to quantify roughness. At all three radar wavelengths, the HV backscatter cross section is found to vary in an approximately exponential fashion with the rms height or Allan deviation at some reference scale, up to a saturation point, where the surface appears entirely diffusely scattering to the radar. Based on these observations, we use a parameter, gamma, defined as the ratio of rms height to the particular scale of measurement. Backscatter values at 24-cm wavelength and the topographic profile data were used to derive expressions which link the HV radar cross section to gamma or to the analogous wavelength-scale rms slope. These equations provide a reasonable fit to 24- and 68-cm echoes and for rough surfaces at 5.7 cm, but yield poor results for 5.7-cm echoes on smooth terrain. We conclude that the roughness at the two larger scales is well described by a single fractal dimension and rms height, but that texture at very small scales is characterized by different statistics. This inference is supported by analysis of 5-cm horizontal spacing topographic profiles. The relationships defined here allow determination of the surface rms height or slope at the scale of the radar wavelength. Given radar data at additional wavelengths, a more complete view of the statistical properties of the surface can be developed. Such techniques may be useful in analyses of synthetic aperture radar images for terrestrial volcanic areas, Magellan data for Venus, and other planetary radar observations.

Interpretation and analysis of planetary structures

Smithsonian Libraries
Structural geology is an integral part of planetary science. Planetary structures provide the framework for determining the character and sequence of crustal deformation while simultaneously establishing the observational basis required to test geodynamic hypotheses for the deformation of planetary and satellite lithospheres. The availability of datasets that record spatial and topographic information with a resolution that matches or, in many cases, exceeds, what is available for Earth-based studies permits the deformation of several planets and satellites to be investigated down to the local or outcrop scales. The geometry and kinematics of common planetary structures such as joints, igneous dikes, deformation bands, faults, and folds can be determined with confidence from their distinctive morphologic and topographic signatures, enabling the structural histories and deformation magnitudes to be determined. Segmentation, displacement profiles, relay-ramps, footwall anticlines, displacement-controlled depocenters, and other well-known characteristics of terrestrial normal fault and graben systems reveal the sequence and processes of fault growth in numerous planetary examples. Systems of thrust faults having both blind and surface-breaking components are important elements on several bodies including Mercury, the Moon, and Mars. Strike-slip faults have been identified on bodies including Mars and Europa with oblique extension found on Ganymede. Using field-based studies of Earth-based structures as a guide, planetary structures provide a means to explore and evaluate the causative stresses. Despite the wide range in structural styles across the solar system, plate tectonics is recognized only on the Earth, with the other planets and satellites deforming in the absence of large-scale horizontal motions and attendant plate recycling.

Evidence for a recent increase in forest growth

Smithsonian Libraries
Forests and their soils contain the majority of the earth's terrestrial carbon stocks. Changes in patterns of tree growth can have a huge impact on atmospheric cycles, biogeochemical cycles, climate change, and biodiversity. Recent studies have shown increases in biomass across many forest types. This increase has been attributed to climate change. However, without knowing the disturbance history of a forest, growth could also be caused by normal recovery from unknown disturbances. Using a unique dataset of tree biomass collected over the past 22 years from 55 temperate forest plots with known land-use histories and stand ages ranging from 5 to 250 years, we found that recent biomass accumulation greatly exceeded the expected growth caused by natural recovery. We have also collected over 100 years of local weather measurements and 17 years of on-site atmospheric CO measurements that show consistent increases in line with globally observed climate-change patterns. Combined, these observations show that changes in temperature and CO that have been observed worldwide can fundamentally alter the rate of critical natural processes, which is predicted by biogeochemical models. Identifying this rate change is important to research on the current state of carbon stocks and the fluxes that influence how carbon moves between storage and the atmosphere. These results signal a pressing need to better understand the changes in growth rates in forest systems, which influence current and future states of the atmosphere and biosphere.

Reading the Complex Skipper Butterfly Fauna of One Tropical Place

Smithsonian Libraries
Background: An intense, 30-year, ongoing biodiversity inventory of Lepidoptera, together with their food plants and parasitoids, is centered on the rearing of wild-caught caterpillars in the 120,000 terrestrial hectares of dry, rain, and cloud forest of Area de Conservacion Guanacaste (ACG) in northwestern Costa Rica. Since 2003, DNA barcoding of all species has aided their identification and discovery. We summarize the process and results for a large set of the species of two speciose subfamilies of ACG skipper butterflies (Hesperiidae) and emphasize the effectiveness of barcoding these species (which are often difficult and time-consuming to identify). Methodology/Principal Findings: Adults are DNA barcoded by the Biodiversity Institute of Ontario, Guelph, Canada; and they are identified by correlating the resulting COI barcode information with more traditional information such as food plant, facies, genitalia, microlocation within ACG, caterpillar traits, etc. This process has found about 303 morphologically defined species of eudamine and pyrgine Hesperiidae breeding in ACG (about 25% of the ACG butterfly fauna) and another 44 units indicated by distinct barcodes (n = 9,094), which may be additional species and therefore may represent as much as a 13% increase. All but the members of one complex can be identified by their DNA barcodes. Conclusions/Significance: Addition of DNA barcoding to the methodology greatly improved the inventory, both through faster (hence cheaper) accurate identification of the species that are distinguishable without barcoding, as well as those that require it, and through the revelation of species "hidden" within what have long been viewed as single species. Barcoding increased the recognition of species-level specialization. It would be no more appropriate to ignore barcode data in a species inventory than it would be to ignore adult genitalia variation or caterpillar ecology.

Conservatism of Late Pennsylvanian vegetational patterns during short-term cyclic and long-term directional environmental change, western equatorial Pangea

Smithsonian Libraries
Patterns of plant distribution by palaeoenvironment were examined across the Pennsylvanian–Permian transition in North–Central Texas. Stratigraphically recurrent packages of distinct lithofacies, representing different habitats, contain qualitatively and quantitatively different macrofloras and microfloras. The species pools demonstrate niche conservatism, remaining closely tied to specific habitats, during both short-term cyclic environmental change and a long-term trend of increasing aridity. The deposits examined principally comprise the terrestrial Markley and its approximate marine equivalent, the Harpersville Formation and parts of lower Archer City Formation. Fossiliferous deposits are lens-like, likely representing fill sequences of channels formed during abandonment phases. Palaeosols, represented by blocky mudstones, comprise a large fraction of the deposits. They suggest progressive climate change from minimally seasonal humid to seasonal subhumid to seasonal dry subhumid. Five lithofacies yielded plants: kaolinite-dominated siltstone, organic shale, mudstone beds within organic shale, coarsening upward mudstone–sandstone interbeds and channel sandstone. Both macro- and microflora were examined. Lithofacies proved compositionally distinct, with different patterns of dominance diversity. Organic shales (swamp deposits), mudstone partings (swamp drainages) and coarsening upward mudstone–sandstone interbeds (floodplains) typically contain Pennsylvanian wetland vegetation. Kaolinite-dominated siltstones and (to the extent known) sandstones contain taxa indicative of seasonally dry substrates. Some kaolinite-dominated siltstones and organic shales/coals yielded palynomorphs. Microfloras are more diverse, with greater wetland–dryland overlap than macrofloras. It appears that these two floras were coexistent at times on the regional landscape.

Numbers Don’t Lie: The CD Really Is Dead

Smithsonian Magazine

As streaming music gains popularity, record companies have insisted it’s not threatening their sales. But newly released statistics suggest that streaming music may be killing a format instead. For the first time ever, streaming revenues have surpassed those made by compact discs.

A new report from the Recording Industry Association of America shows that streaming outlets generated $1.87 billion in 2014—while CD sales fell to $1.85 billion. Streaming music’s edge is slight but significant: it now accounts for 27 percent of the industry’s total revenues. And while permanent downloads still dominate the digital music market (with $2.58 billion in revenues, they bring in about 38 percent more than streaming services), streaming is catching up quickly.

With digital music now capturing 65 percent of the market’s revenues, it’s easy to predict the demise of all physical formats. But there is one dark horse in the game. The RIAA’s report also showed that vinyl sales continue to rise (revenues are up 50 percent since 2013). LPs have staged what the Wall Street Journal calls “the biggest music comeback of 2014,” and the format is making gains with the same under-35 demographic that’s fueling streaming music. 

The humble CD isn’t the only format that’s being edged out by a changing music market, either. Streaming music is threatening another mainstay: the car radio. The New York Post reports that terrestrial radio is being edged out by streaming services like Sirius XM and Pandora—and by 2018, more than 60 percent of new vehicles in the United States will come equipped with the technology it takes to stream on the go.


National Museum of American History
This theodolite magnetometer is based on the design that the U.S. Coast and Geodetic Survey developed in 1892-1893. It is similar in many ways to the instrument that the Survey had been using since the early 1880s, but with several new features. One is the octagonal shape of the collimating magnets. Another is the black velvet screen that connects the telescope with the suspension box: this cuts off stray light and eliminates the problems that had been caused by the glass window in the earlier form. It is marked "FAUTH & CO. WASHN D.C. 941" and "T.M.C.I. 1." The serial number suggests that it was made around 1895. This instrument belonged to the Department of Terrestrial Magnetism of the Carnegie Institution of Washington. Internal records indicate that D.T.M. purchased it from Kolesch & Co. in New York in 1906 (for $175), sent it to Bausch, Lomb, Saegmuller Co. for repairs (another $120), and kept it in service until 1919. Ref: Edwin Smith, "Notes on Some Instruments Recently Made in the Instrument Division of the Coast and Geodetic Survey Office," Annual Report of the Superintendent of the U.S. Coast and Geodetic Survey for 1894, Appendix No. 8.

Giant boid snake from the Palaeocene neotropics reveals hotter past equatorial temperatures

Smithsonian Libraries
The largest extant snakes live in the tropics of South America and southeast Asia1, 2, 3 where high temperatures facilitate the evolution of large body sizes among air-breathing animals whose body temperatures are dependant on ambient environmental temperatures (poikilothermy)4, 5. Very little is known about ancient tropical terrestrial ecosystems, limiting our understanding of the evolution of giant snakes and their relationship to climate in the past. Here we describe a boid snake from the oldest known neotropical rainforest fauna from the Cerrejón Formation (58–60 Myr ago) in northeastern Colombia. We estimate a body length of 13 m and a mass of 1,135 kg, making it the largest known snake6, 7, 8, 9. The maximum size of poikilothermic animals at a given temperature is limited by metabolic rate4, and a snake of this size would require a minimum mean annual temperature of 30–34 °C to survive. This estimate is consistent with hypotheses of hot Palaeocene neotropics with high concentrations of atmospheric CO2 based on climate models10. Comparison of palaeotemperature estimates from the equator to those from South American mid-latitudes indicates a relatively steep temperature gradient during the early Palaeogene greenhouse, similar to that of today. Depositional environments and faunal composition of the Cerrejón Formation indicate an anaconda-like ecology for the giant snake, and an earliest Cenozoic origin of neotropical vertebrate faunas.

The Major-Element Composition of Mercury’s Surface from MESSENGER X-ray Spectrometry

Smithsonian Libraries
X-ray fluorescence spectra obtained by the MESSENGER spacecraft orbiting Mercury indicate that the planet’s surface differs in composition from those of other terrestrial planets. Relatively high Mg/Si and low Al/Si and Ca/Si ratios rule out a lunarlike feldspar-rich crust. The sulfur abundance is at least 10 times higher than that of the silicate portion of Earth or the Moon, and this observation, together with a low surface Fe abundance, supports the view that Mercury formed from highly reduced precursor materials, perhaps akin to enstatite chondrite meteorites or anhydrous cometary dust particles. Low Fe and Ti abundances do not support the proposal that opaque oxides of these elements contribute substantially to Mercury’s low and variable surface reflectance.


National Museum of American History
This is a direct-vision spectroscope with a seven-part prism. The three sections (collimator, prism train and telescope) screw together to form an instrument 18 inches long overall. The “John Browning / London” inscription refers to John Browning (ca. 1831-1925), the first important English spectroscope maker. The “Alex. R. Newman” inscription on the top of the mahogany box has not been identified. The “1173” incised on the inside of the box may be a serial number. Browning introduced the seven prism form in 1869. A reliable text published in 1872 stated that this instrument “commends itself by the excellence of its performance, the facility of its use, the smallness of its dimension, the purity of colour, and its low price.” Ref: John Browning, How to Work with the Spectroscope (London / New York, 1878). H. Schellen, Spectrum Analysis in its Application to Terrestrial Substances, and the Physical Constitution of the Heavenly Bodies (London, 1872), p. 119.

Priming depletes soil carbon and releases nitrogen in a scrub-oak ecosystem exposed to elevated CO2

Smithsonian Libraries
Elevated atmospheric CO2 tends to stimulate plant productivity, which could either stimulate or suppress the processing of soil carbon, thereby feeding back to atmospheric CO2 concentrations. We employed an acid-hydrolysis-incubation method and a net nitrogen-mineralization assay to assess stability of soil carbon pools and short-term nitrogen dynamics in a Florida scrub-oak ecosystem after six years of exposure to elevated CO2. We found that soil carbon concentration in the slow pool was 27% lower in elevated than ambient CO2 plots at 0-10 cm depth. The difference in carbon mass was equivalent to roughly one-third of the increase in plant biomass that occurred in the same experiment. These results concur with previous reports from this ecosystem that elevated CO2 stimulates microbial degradation of relatively stable soil organic carbon pools. Accordingly, elevated CO2 increased net N mineralization in the 10-30 cm depth, which may increase N availability, thereby allowing for continued stimulation of plant productivity by elevated CO2. Our findings suggest that soil texture and climate may explain the differential response of soil carbon among various long-term, field-based CO2 studies. Increased mineralization of stable soil organic carbon by a CO2-induced priming effect may diminish the terrestrial carbon sink globally.

Cary 12-Inch Celestial Globe

National Museum of American History
The cartouche reads “CARY’S / NEW / CELESTIAL GLOBE, / are correctly laid down upwards of 3500 stars / selected from the most accurate observations / and calculated for the year 1800. / With the extent of each constellation precisely defined / By Mr. GILPIN of the ROYAL SOCIETY. / Made and Sold by J. & W. CARY. / Strand London Jan. 1 1816.” The globe is held on a wooden pedestal with three curved legs. It has a wooden horizon circle and a brass meridian. John Cary was a globe maker in London who began in business in 1791. For this globe (and a few other things) he worked with his brother William. George Gilpin worked as an assistant at the Royal Observatory at Greenwich for a couple of years, and as the clerk of the Royal Society of London from 1785 until his death in 1810. Cary introduced his new 12-inch celestial globe and the terrestrial mate in 1798. This example is dated 1816. Ref: Herbert George Fordham, John Cary: Engraver, Map, Chart and Print-Seller and Globe-Maker, 1754 to 1835 (Cambridge, 1925)

An analysis of sinuous ridges in the southern Argyre Planitia, Mars using HiRISE and CTX images and MOLA data

Smithsonian Libraries
A suite of sinuous ridges with branching and braided morphologies forms an anastomosing network in southern Argyre Planitia, Mars. Several modes of origin have been proposed for the Argyre ridges. Imagery from the High Resolution Imaging Science Experiment (HiRISE) and Context Camera (CTX) aboard Mars Reconnaissance Orbiter (MRO) and Mars Orbiter Laser Altimeter (MOLA) topographic data sets from Mars Global Surveyor (MGS) are used to constrain processes involved in formation of the Argyre ridges. We find the characteristics of the ridges and associated layered deposits consistent with glaciofluvial-lacustrine processes and conclude that the ridges are most likely eskers. In particular, variations in ridge height appear to be related to the surrounding surface slope; ridge height increases with descending slopes and decreases with ascending slopes. This characteristic is observed in terrestrial eskers and is related to subice flow processes. The nature of some eroding beds in the ridges suggests induration. If the Argyre ridges are indeed eskers, the southern Argyre basin was once covered by the margin of a large, thick, stagnating or retreating ice deposit that extended for hundreds of kilometers or more. During ridge formation, water flowed on top, within, or beneath the ice deposit; the continuity and preservation of the ridges suggests that flow was primarily at the base of the ice. The dimensions (up to hundreds of meters tall and several kilometers wide), aspect ratio, and extent (hundreds of kilometers) of the ridges, as well as preliminary calculations of discharge, suggest that a significant amount of water was available.

Calibrating the End-Permian Mass Extinction

Smithsonian Libraries
The end-Permian mass extinction was the most severe biodiversity crisis in Earth history. To better constrain the timing, and ultimately the causes of this event, we collected a suite of geochronologic, isotopic, and biostratigraphic data on several well-preserved sedimentary sections in South China. High-precision U-Pb dating reveals that the extinction peak occurred just before 252.28 +/- 0.08 million years ago, after a decline of 2 per mil (parts per thousand) in delta(13)C over 90,000 years, and coincided with a delta(13)C excursion of -5 parts per thousand that is estimated to have lasted <= 20,000 years. The extinction interval was less than 200,000 years and synchronous in marine and terrestrial realms; associated charcoal-rich and soot-bearing layers indicate widespread wildfires on land. A massive release of thermogenic carbon dioxide and/or methane may have caused the catastrophic extinction.

Stable Carbon and Oxygen Isotope Spacing Between Bone and Tooth Collagen and Hydroxyapatite in Human Archaeological Remains

Smithsonian Libraries
Spacing between stable isotope values in bones and teeth is a valuable tool for examining dietary influences and diagenesis. This study examines carbon and oxygen isotope values from collagen and hydroxyapatite (structural carbonate and phosphate) in archaeological human bones and teeth to derive species-specific correlation equations and isotope spacing values. The ?13Ccollagen and ?13Cstructural carbonate in bone and dentin collagen show a strong correlation (R = 0.87, 0.90, respectively) with an average ?13Ccarb-coll spacing of 5.4?. The consistency of this isotope spacing with other large mammals and in humans with both low and high protein intake (as indicated by enriched ?15N values) suggests a similar allocation of protein-derived carbon and whole diet-derived carbon to collagen and structural carbonates, respectively, as other terrestrial mammals regardless of absolute meat intake. The ?18Ostructural carbonate and ?18Ophosphate show the strongest correlation in enamel (R = 0.65), weaker correlations in dentin (R = 0.59) and bone (R = 0.35), with an average ?18Ocarb-phos of 7.8?. This isotope spacing is slightly lower than previously reported for large mammals and limited available data for humans. The results potentially indicate species-specific fractionations and differing access to body water and blood-dissolved inorganic carbonates in the presence of collagen formation. The use of correlation between ?18Ostructural carbonate and ?18Ophosphate to determine diagenetic state is not recommended. The strength of this correlation observed in bones and teeth is variable and alternate indicators of diagenetic state (i.e. C:N ratios of collagen) provide more robust and independent evidence of isotope preservation despite presence/absence of a strong isotope correlation. Published 2012. This article is a U.S. Government work and is in the public domain in the USA.

Saxton Metallic Thermometer

National Museum of American History
Joseph Saxton, an accomplished scientist, inventor, and mechanician, joined the staff of the U.S. Coast Survey in 1844 at the request of the new Superintendent, Alexander Dallas Bache, and began developing instruments for measuring various terrestrial phenomena. Among the first was a metallic thermometer for use in deep water. Bache described this in 1848, saying that it proved “decidedly the most convenient” of the several forms tried. The thermometer coil was “like that of Breguet, only of much stouter material, and of two metals, silver and platinum, soldered together.” And the “plan of registering resembles that adopted by Jurgensen of Copenhagen, and by Montandon of Washington, in their metallic thermometers.” Several of Saxton’s thermometers were made in the Coast Survey’s instrument shop, and were still in use at the start of World War I. This example came to the Smithsonian in 1929. Here the thermometer is held in a brass cylinder that is encased in a hexagonal frame. The cap of the cylinder is marked “SAXTON’S / METALLIC THERMOMETER / 17.” The scale around the circumference of the thermometer extends from -40 to +174 degrees Fahrenheit; one of the two pointers registers the lowest temperature to which the thermometer was exposed. Ref: [A. D. Bache], Report of the superintendent of the coast survey, showing the progress of the work during the year ending November, 1848, p. 39. Bache, “Lecture on the Gulf Stream, prepared at the request of the American Association for the Advancement of Science,” Report of the Superintendent of the Coast Survey during the Year 1860, pp. 165-176, on 166.
39121-39144 of 39,370 Resources