Tuesday, June 18, 2013
As the closest planet to Earth, Venus is a relatively easy object to observe. However, many mysteries remain, not least the super-rotation of Venus' atmosphere, which enables high altitude winds to circle the planet in only four days. Now images of cloud features sent back by ESA's Venus Express orbiter have revealed that these remarkably rapid winds are becoming even faster.
The drift history of Adria and Africa from 280 Ma to Present, Jurassic true polar wander, and zonal climate control on Tethyan sedimentary facies
1. G. Muttoni (a, b)
2. E. Dallanave (c)
3. J.E.T. Channell (d)
a. Dipartimento di Scienze della Terra "A. Desio", Università degli Studi di Milano, via Mangiagalli 34, 20133 Milano, Italy
b. ALP - Alpine Laboratory of Paleomagnetism, via Madonna dei Boschi 76, I-12016 Peveragno (CN), Italy
c. Department of Earth and Environmental Science, Ludwig-Maximilians University, Munich D-80333, Germany
d. Department of Geological Sciences, University of Florida, Gainesville, FL 32611, USA
The orogenic belts surrounding the undeformed Adriatic Sea represent the margins of an area known as Adria, the African promontory. We have undertaken a critical appraisal of paleomagnetic data from regions of Adria considered parautochthonous relative to Africa and obtained either from biostratigraphically dated sedimentary rocks, corrected for inclination shallowing, or from igneous rocks that are regarded as free from any inclination shallowing bias. Paleomagnetic directions were used to calculate paleomagnetic poles for comparison with coeval, and inclination flattening-free, paleomagnetic poles from stable Africa. Visual coherence of paleopoles for several time slices from the Early Permian to the Eocene supports the construction of a composite apparent polar wander path (APWP) valid for parautochthonous Adria and stable Africa. This composite APWP is compared to previous APWPs, finding good agreement with the global APWP of Kent and Irving (2010). Both APWPs show a remarkable and rapid polar shift of ~ 40° in the Jurassic that other APWPs tend to underestimate. We interpret this shift to represent a major episode of true polar wander (TPW), from ~ 183 Ma in the Early Jurassic to ~ 151 Ma in the Late Jurassic. Using a simple zonal climate model, the drift motion of Adria attached to Africa appears to be consistent with the distribution of Permian–Cretaceous sedimentary facies on Adria.
3D printing can now be used to print lithium-ion microbatteries the size of a grain of sand. The printed microbatteries could supply electricity to tiny devices in fields from medicine to communications, including many that have lingered on lab benches for lack of a battery small enough to fit the device, yet provide enough stored energy to power them.
To make the microbatteries, a team based at Harvard University and the University of Illinois at Urbana-Champaign printed precisely interlaced stacks of tiny battery electrodes, each less than the width of a human hair.
"Not only did we demonstrate for the first time that we can 3D-print a battery, we demonstrated it in the most rigorous way," said Jennifer Lewis, Ph.D., senior author of the study, who is also the Hansjörg Wyss Professor of Biologically Inspired Engineering at the Harvard School of Engineering and Applied Sciences (SEAS), and a Core Faculty Member of the Wyss Institute for Biologically Inspired Engineering at Harvard University. Lewis led the project in her prior position at the University of Illinois at Urbana-Champaign, in collaboration with co-author Shen Dillon, an Assistant Professor of Materials Science and Engineering there.
The results will be published online on June 18 in the journal Advanced Materials.
Trophic cascade alters ecosystem carbon exchange
1. Michael S. Strickland (a,b)
2. Dror Hawlena (c)
3. Aspen Reese (a,d)
4. Mark A. Bradford (a)
5. Oswald J. Schmitz (a)
a. School of Forestry and Environmental Studies, Yale University, New Haven, CT 06511
b. Department of Biological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061
c. Department of Ecology, Evolution and Behavior, The Alexander Silberman Institute of Life Sciences, Hebrew University of Jerusalem, Givat-Ram, Jerusalem 91904, Israel
d. Department of Biology, Duke University, Durham, NC 27708
Trophic cascades—the indirect effects of carnivores on plants mediated by herbivores—are common across ecosystems, but their influence on biogeochemical cycles, particularly the terrestrial carbon cycle, are largely unexplored. Here, using a 13C pulse-chase experiment, we demonstrate how trophic structure influences ecosystem carbon dynamics in a meadow system. By manipulating the presence of herbivores and predators, we show that even without an initial change in total plant or herbivore biomass, the cascading effects of predators in this system begin to affect carbon cycling through enhanced carbon fixation by plants. Prolonged cascading effects on plant biomass lead to slowing of carbon loss via ecosystem respiration and reallocation of carbon among plant aboveground and belowground tissues. Consequently, up to 1.4-fold more carbon is retained in plant biomass when carnivores are present compared with when they are absent, owing primarily to greater carbon storage in grass and belowground plant biomass driven largely by predator nonconsumptive (fear) effects on herbivores. Our data highlight the influence that the mere presence of predators, as opposed to direct consumption of herbivores, can have on carbon uptake, allocation, and retention in terrestrial ecosystems.
Monday, June 17, 2013
Cambrian lobopodians: A review of recent progress in our understanding of their morphology and evolution
1. Jianni Liu (a)
2. Jason A. Dunlop (b)
a. Early Life Institute, The Key Laboratory of Continental Dynamics, Northwest University, Xi’an, 710069, China
b. Museum für Naturkunde, Leibniz Institute for Research on Evolution, and Biodiversity at the Humboldt University Berlin, D-10115 Berlin, Germany
Lobopodians are an important group of organisms which appeared during the Cambrian Explosion. The underlying morphology is invariably a worm-like body bearing multiple pairs of legs. Yet in detail these animals preserve a range of morphologies and have attracted much palaeontological attention; particularly since this assemblage probably includes the ancestors of living velvet worms (Onychophora), water bear (Tardigrada) and arthropods (Arthropoda). In recent years, knowledge of Cambrian lobopodians has increased dramatically based on numerous new records. However, there have been few comprehensive reviews of these animals since Ramsköld & Chen's study in 1998. In the present paper, new insights into Cambrian lobopodians are presented. The legs of Aysheaia pedunculata have a strong attachment with the body, like those of lobopodians in the Chengjiang Fauna. Hallucigenia fortis has a pair of eyes, two pairs of tentacles are observed in the 'neck' region while a bivalved head shield is unequivocally lacking. Some new characters for, and the orientation of, Hallucigenia sparsa are discussed. Longitudinal wrinkles on the body of Xenusion auerswalde are regarded here as putative muscles. Cardiodictyon sinicum bears doublure structures at the anterior margin of head and a pair of eye spots; the shape of dorsal plates is also reinterpreted. Onychodictyon has a pair of anterior appendages, but no sclerotized head shield. The affinities of Miraluolishania haikouensis are clarified and the proposal that M. haikouensis is a junior synonym of Luolishania longicruris is refuted. The large lobopodians, Kerygmachela, Jianshanopodia and Megadictyon – all with frontal appendages, gill-like limbs and tree-like or lamellate-like branches – may be swimming predators.
Hemichordata (Pterobranchia, Enteropneusta) and the fossil record
1. Jörg Maletz (a)
a. FU Berlin, Institut für Geologische Wissenschaften, Malteser Str. 74–100, Haus B 322, D- 12247 Berlin, Germany
The Hemichordata are generally interpreted as early deuterostomes, closely related to the chordates, a notion important for modern analyses of the origin of the deuterostomes. Because their fossil record is quite scanty, modern phylogenetic interpretations largely rely on analysis of DNA of the available extant taxa. The tripartite body plan of the group of worm-like hemichordates, the Enteropneusta, may be traced back in deep time to a few poorly known Middle Cambrian (Series 3, Stage 5) taxa from the Burgess Shale biota. The derived small, colonial or pseudocolonial Pterobranchia (Cephalodiscida and Graptolithina) have a more complete fossil record due to their preservable housing construction, the tubarium. The relationships of fossil taxa, putatively identified as early deuterostomes and possible hemichordates or even as pterobranchs of Lower to Middle Cambrian age (e.g. Galeaplumosus, Herpetogaster), cannot be substantiated. The Pterobranchia and their housing construction is first seen in the Middle Cambrian Series 3, Stage 5 but a clonal, colonial organization of the tubaria can only be recognized in the basal Drumian. The fossil enteropneust Mazoglossus ramsdelli Bardack, 1997 from the Carboniferous Mazon Creek Biota is re-described, its lectotype designated and illustrated for the first time.
Sunday, June 16, 2013
Saturday, June 15, 2013
Friday, June 14, 2013
The Archaeopteryx, which lived around 150 million years ago and was a mixture of bird traits (notably feathers) and reptile traits (teeth, claws on its wings), was previously thought to have black feathers. But a new analysis of three Archaeopteryx fossils has revealed that the ancient bird's feathers were in fact light in color, with a dark edge and tips.
The distinct black-and-white patterns on the bird's plumage are comparable to the pigmentation of a magpie, said study co-author Roy Wogelius, a geochemist at the University of Manchester.
"This creature was actually doing very well in terms of evolutionary state. It already has a key adaptation that we see in many modern species of bird," said study leader and University of Manchester paleontologist Phil Manning, who is a National Geographic grantee.
Like modern-day birds, the Archaeopteryx would have benefited from the different shadings.
The scan found traces of copper that produced the dark tips of the bird's feather; copper has properties that can keep away bacteria that would otherwise fray wings. The copper also slowed the "microbial breakdown" of the fossil, Manning notes: "It's the reason the feather has been preserved for 150 million years to the point where we still see astounding resolution in the fossil."
TWO PLANETARY COMPANIONS AROUND THE K7 DWARF GJ 221: A HOT SUPER-EARTH AND A CANDIDATE IN THE SUB-SATURN DESERT RANGE
1. Pamela Arriagada (a,b)
2. Guillem Anglada-Escudé (b,c)
3. R. Paul Butler (b)
4. Jeffrey D. Crane (d)
5. Stephen A. Shectman (d)
6. Ian Thompson (d)
7. Sebastian Wende (c)
8. Dante Minniti (a,e,f)
a. Department of Astronomy, Pontificia Universidad Católica de Chile, Casilla 306, Santiago 22, Chile
b. Department of Terrestrial Magnetism, Carnegie Institution of Washington, 5241 Broad Branch Road NW, Washington, DC 20015-1305, USA
c. Institut für Astrophysik, Universität Göttingen, Friedrich-Hund-Platz 1, D-37077 Göttingen, Germany
d. The Observatories of the Carnegie Institution of Washington, 813 Santa Barbara Street, Pasadena, CA 91101, USA
e. Vatican Observatory, V00120 Vatican City State, Italy
f. Departamento de Ciencia Físicas, Universidad Andrés Bello, Santiago, Chile
We report two low-mass companions orbiting the nearby K7 dwarf GJ 221 that have emerged from reanalyzing 4.4 yr of publicly available HARPS spectra complemented with 2 years of high-precision Doppler measurements with Magellan/PFS. The HARPS measurements alone contain the clear signal of a low-mass companion with a period of 125 days and a minimum mass of 53.2 M ⊕ (GJ 221b), falling in a mass range where very few planet candidates have been found (sub-Saturn desert). The addition of 17 PFS observations allows the confident detection of a second low-mass companion (6.5 M ⊕) in a hot orbit (3.87 day period, GJ 221c). Spectroscopic and photometric calibrations suggest that GJ 221 is slightly depleted ([Fe/H] ~ –0.1) compared to the Sun, so the presence of two low-mass companions in the system confirms the trend that slightly reduced stellar metallicity does not prevent the formation of planets in the super-Earth to sub-Saturn mass regime.
This week in the journal Science, Swedish and Australian researchers present the miraculously preserved musculature of 380 million year old fossil fishes, revealed by unique fossils from a locality in north-west Australia. The finds will help scientists to understand how neck muscles and abdominal muscles – "abs" – evolved.
The word "fossil" naturally conjures up a vision of rattling skeletons. Bones and teeth fossilize far more easily than soft tissues and are usually the only traces of the animal that remain. This makes the rare fossil localities that preserve soft tissues all the more valuable as windows on the biology of extinct organisms.
The Gogo Formation, a sedimentary rock formation in north-western Australia, has long been famous for yielding exquisitely preserved fossil fishes. Among other things it contains placoderms, an extinct group that includes some of the earliest jawed fishes.
A few years ago, Australian researchers discovered that these fossils also contain soft tissues: now they have collaborated with the research group of Professor Per Ahlberg, Uppsala University, and with the ESRF synchrotron in Grenoble, France, to document and reconstruct the musculature of the placoderms.
They prove to have a well-developed neck musculature as well as powerful abdominal muscles – not unlike the human equivalents displayed on the beaches of the world every summer. Living fishes, by contrast, usually have a rather simple body musculature without such specializations.
"This shows that vertebrates developed a sophisticated musculature much earlier than we had thought" says Per Ahlberg, joint leader of the project with Dr Kate Trinajstic of Curtin University in Perth, Western Australia; "It also cautions against thinking that we can interpret fossil organisms simply by metaphorically draping their skeletons in the soft tissues of living relatives."
Taxonomic review of the Ornithocheirus complex (Pterosauria) from the Cretaceous of England
1. Taissa Rodrigues (a)
2. Alexander Wilhelm Armin Kellner (b)
a. Department of Biology, Agrarian Sciences Center, Universidade Federal do Espírito Santo. Alto Universitário s/n, Caixa Postal 16, Guararema, CEP 29500–000, Alegre, ES, Brazil
b. Laboratory of Systematics and Taphonomy of Fossil Vertebrates, Department of Geology and Paleontology, Museu Nacional / Universidade Federal do Rio de Janeiro. Quinta da Boa Vista s/n, São Cristóvão, CEP 20940–040, Rio de Janeiro, RJ, Brazil
Over a decade after the last major review of the Cambridge Greensand pterosaurs, their systematics remains one of the most disputed points in pterosaur taxonomy. Ornithocheiridae is still a wastebasket for fragmentary taxa, and some nomenclatural issues are still a problem. Here, the species from the Cretaceous of England that, at some point, were referred in Ornithocheirus, are reviewed. Investigation of the primary literature confirmed that Criorhynchus should be considered an objective junior synonym of Ornithocheirus. Taxonomic review of more than 30 species known from fragmentary remains showed that 16 of them are undiagnosable (nomina dubia): Palaeornis cliftii, Cimoliornis diomedeus, Pterodactylus compressirostris, Pterodactylus fittoni, Pterodactylus woodwardi, Ornithocheirus brachyrhinus, Ornithocheirus carteri, Ornithocheirus crassidens, Ornithocheirus dentatus, Ornithocheirus enchorhynchus, Ornithocheirus eurygnathus, Ornithocheirus oxyrhinus, Ornithocheirus scaphorhynchus, Ornithocheirus tenuirostris, Ornithocheirus xyphorhynchus, and Pterodactylus sagittirostris. Fourteen species are considered valid, and diagnoses are provided to all of them: Ornithocheirus simus, Lonchodraco giganteus comb. n., Lonchodraco machaerorhynchus comb. n., Lonchodraco(?) microdon comb. n., Coloborhynchus clavirostris, ‘Ornithocheirus’ capito, Camposipterus nasutus comb. n., Camposipterus(?) sedgwickii comb. n., Camposipterus(?) colorhinus comb. n., Cimoliopterus cuvieri comb. n., ‘Ornithocheirus’ polyodon, ‘Ornithocheirus’ platystomus, ‘Pterodactylus’ daviesii, and ‘Ornithocheirus’ denticulatus. These species are referred in the genera Ornithocheirus, Lonchodraco gen. n., Coloborhynchus, Cimoliopterus gen. n., and Camposipterus gen. n., but additional genera are probably present, as indicated by the use of single quotation marks throughout the text. A cladistic analysis demonstrates that Anhangueridae lies within a newly recognized clade, here named Anhangueria, which also includes the genera Cearadactylus, Brasileodactylus, Ludodactylus, and Camposipterus. The anhanguerian ‘Cearadactylus’ ligabuei belongs to a different genus than Cearadactylus atrox. Lonchodraconidae fam. n. (more or less equivalent to Lonchodectidae sensu Unwin 2001) is a monophyletic entity, but its exact phylogenetic position remains uncertain, as is the case of Ornithocheirus simus. Therefore, it is proposed that Ornithocheiridae should be constricted to its type species and thus is redundant. Other taxa previously referred as “ornithocheirids” are discussed in light of the revised taxonomy.
Thursday, June 13, 2013
For obvious reasons, everyone talks about a world dominated by China. China is likely to have an economy which will be x times larger than the US on the future's horizon. For the moment, assume the economic size is remains tied to the population size. Which case, the projections I have seen for India's population in 2050 is larger than China's by a fair bit. if the world stabilizes around then, population wise, circa 2100 its probable India will have a larger economy than China will, even if they have the same per capita economy. Even more so, should China be unsuccessful in reversing the one child policy, say, because the family size has become cultural, this could be even worse (though to be fair, India's TFR has fallen considerably, too. It does remain above replacement).
Projecting 2100 with rigor is hard. However, that's never stopped science fiction! On the other hand, let's try to keep a little rigor here. What WOULD an Indian dominated world look like?
"We hold that a naturally occurring DNA segment is a product of nature and not patent eligible merely because it has been isolated," Thomas said.
A team of researchers has discovered evidence that an extrasolar planet may be forming quite far from its star—- about twice the distance Pluto is from our Sun. The planet lies inside a dusty, gaseous disk around a small red dwarf TW Hydrae, which is only about 55 percent of the mass of the Sun. The discovery adds to the ever-increasing variety of planetary systems in the Milky Way. The research is published in the Astrophysical Journal.*
This dusty protoplanetary disk is the closest one to us, some 176 light-years away in the constellation Hydra. The astronomers made Hubble Space Telescope observations over a wide range of wavelengths from visible to near infrared and modeled the color and structure of the disk in a way that has not been done before. They found a deficit of disk material, or partial gap, at about 80 astronomical units (AU) (1 AU is the Earth/Sun distance). Their models indicate that the depression is about 20 AUs wide, just slightly wider than necessary for a planet-opening gap and consistent with a planet of between 6 and 28 Earth masses. The feature is seen at all wavelengths indicating it is structural and not a local compositional difference. The team believes the evidence is strong for planet formation causing the gap.
"TW Hydrae is between 5 and 10 million years old, and should be in the final throes of planet formation before its disk dissipates," remarked coauthor Alycia Weinberger of the Carnegie Institution and principal investigator of the observations. "It is surprising to find a planet only 5 to 10% of Jupiter's mass forming so far out since planets should form faster closer in. In all planet formation scenarios, it's difficult to make a low-mass planet far away from a low mass star."
The goal of these observations was to understand not only whether planets have formed, but also what conditions can result in planet formation and what chemical constituents are available for new planets. Models by coauthor Hannah Jang-Condell, a former Carnegie postdoctoral researcher, showed that the disk was brighter than expected, which indicates that very small dust grains are being lifted high above the midplane. This is surprising because observations with radio telescopes have previously shown that the disk contains dust that has conglomerated into pebbles.
Weinberger designed the observations to be able to detect large water ice grains in the surface layer of the disk. These grains weren't seen, which probably means that they have grown and sunk to the midplane of the disk where they can aggregate into water-rich planets.
Planet formation far away from a small parent star is at odds with the conventional planet-making [model]. Under the most accepted scenario, planets form over tens of millions of years from the slow accretion of dust, rocks, and gas. That happens most easily close to the central star, where orbital timescales are short. Even under a disk instability scenario, in which planets can collapse quickly from the disk, it's not clear such a low mass planet could form.
Terminal Proterozoic cyanobacterial blooms and phosphogenesis documented by the Doushantuo granular phosphorites I: In situ micro-analysis of textures and composition
1. Zhenbing She (a, b)
2. Paul Strother (c)
3. Gregory McMahon (d)
4. Larry R. Nittler (e)
5. Jianhua Wang (e)
6. Jianhua Zhang (f)
7. Longkang Sang (a)
8. Changqian Ma (a, b)
9. Dominic Papineau (c, g)
a. State Key Laboratory of Geological Processes and Mineral Resources, Wuhan 430074, China
b. Faculty of Earth Sciences, China University of Geosciences, Wuhan 430074, China
c. Department of Earth and Environmental Sciences, Boston College, Chestnut Hill, MA 02467, USA
d. Nanofabrication Cleanroom Facility, Boston College, Newton, MA 02459, USA
e. Department of Terrestrial Magnetism, Carnegie Institution of Washington, Washington DC 20015, USA
f. Mine Planning and Designing Institute of Yilin District, Yichang 443100, China
g. Geophysical Laboratory, Carnegie Institution of Washington, Washington DC 20015, USA
In order to ascertain the origin of granular phosphorites and the roles of microorganisms in phosphogenesis, we conducted comprehensive petrographic surveys and correlated in situ micro-analyses of granular phosphorites from the Doushantuo Formation near Yichang, South China. Phosphatic granules display organically-zoned internal structures often associated with abundant cyanobacteria-like microfossils. The internal ultrastructure of the granules, as documented by Raman microspectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM), is characterized by randomly-oriented apatite nano-crystals embedded with ubiquitous carbonaceous particles in the apatite groundmass. These represent primary textures formed by the rapid growth of apatite provided with abundant nucleation sites within microbial biofabrics. NanoSIMS elemental mapping revealed close correspondence of carbon and nitrogen with microfossil structures at the cellular and sub-cellular level. We propose that the Doushantuo granules themselves were formed by microbially-mediated accretionary growth followed by rapid phosphatization occurring at the sediment-water interface. Extracellular polymeric substances (EPS) produced by cyanobacteria would have played crucial roles in these processes by promoting aggregated granule growth in addition to providing nucleation sites for apatite crystallization. While previous studies have suggested a dominant role of sulfur-metabolizing microorganisms in the precipitation of phosphate in phosphorites, new observations indicate that the emplacement of most sulfur-bearing minerals in the Doushantuo phosphorites postdate phosphatization itself. Our new model of phosphorite formation thus places cyanobacterial EPS as an earlier key component of the mineralization of the Doushantuo granular phosphorites.
Constraining the Air Giants: Limits on Size in Flying Animals as an Example of Constraint-Based Biomechanical Theories of Form
1. Mike Habib (a)
a. Department of Cell and Neurobiology, University of Southern California, Los Angeles, CA, USA
The study of biomechanics most often takes a classic adaptationist approach, examining the functional abilities of organisms in relation to what is allowed by physical parameters. This approach generally assumes strong selection and is less concerned with evolutionary stochasticity in determining the presence of biological traits. It is equally important, however, to consider the importance of constraint in determining the form of organisms. If selection is relatively weak compared to stochastic events, then the observed forms in living systems can be taken not as those shapes that were strongly selected for, so much as those forms that do not violate physical rules and therefore persist. Using the problem of maximum animal size as a case study for this alternative biomechanical philosophy, I demonstrate one example of how biomechanical approaches can be used to study constraint and consider the concept of absent forms. This alternative mindset and approach produces a complementary system to the traditional form and function approach in biomechanics. The two philosophies can be used in conjunction to better understand biological systems. I focus particularly on the maximum size of flying animals, as they are a heavily constrained class of system that has also been shaped by substantial stochasticity.
Wednesday, June 12, 2013
Eocene cooling linked to early flow across the Tasmanian Gateway
1. Peter K. Bijl (a)
2. James A. P. Bendle (b)
3. Steven M. Bohaty (c)
4. Jörg Pross (d,e)
5. Stefan Schouten (f)
6. Lisa Tauxe (g)
7. Catherine E. Stickley (h)
8. Robert M. McKay (i)
9. Ursula Röhl (j)
10. Matthew Olney (k)
11. Appy Sluijs (a)
12. Carlota Escuti (a,l)
13. Henk Brinkhuis (a,f)
14. Expedition 318 Scientists
a. Department of Earth Sciences, Faculty of Geosciences, Utrecht University, 3584 CD, Utrecht, The Netherlands
b. Geographical and Earth Sciences, University of Glasgow, Glasgow G12 8QQ, United Kingdom
c. Ocean and Earth Science, University of Southampton, Southampton SO14 3ZH, United Kingdom
d. Paleoenvironmental Dynamics Group, Institute of Geosciences, University of Frankfurt, 60438 Frankfurt, Germany
e. Biodiversity and Climate Research Centre, 60325 Frankfurt, Germany
f. NIOZ Royal Netherlands Institute for Sea Research, 1790 AB, Den Burg, Texel, The Netherlands
g. Geosciences Research Division, Scripps Institution of Oceanography, University of California at San Diego, La Jolla, CA 92093-0220
h. Department of Geology, University of Troms, N-9037 Troms, Norway
i. Antarctic Research Centre, Victoria University of Wellington, Wellington 6140, New Zealand
j. MARUM–Center for Marine Environmental Sciences, University of Bremen, 28359 Bremen, Germany
k. Department of Geology, University of South Florida, Tampa, FL 33620
l. Instituto Andaluz de Ciencias de la Tierra, Consejo Superior de Investigaciones Cientificas (Spain)–Universite de Granada, 18002 Granada, Spain
The warmest global temperatures of the past 85 million years occurred during a prolonged greenhouse episode known as the Early Eocene Climatic Optimum (52–50 Ma). The Early Eocene Climatic Optimum terminated with a long-term cooling trend that culminated in continental-scale glaciation of Antarctica from 34 Ma onward. Whereas early studies attributed the Eocene transition from greenhouse to icehouse climates to the tectonic opening of Southern Ocean gateways, more recent investigations invoked a dominant role of declining atmospheric greenhouse gas concentrations (e.g., CO2). However, the scarcity of field data has prevented empirical evaluation of these hypotheses. We present marine microfossil and organic geochemical records spanning the early-to-middle Eocene transition from the Wilkes Land Margin, East Antarctica. Dinoflagellate biogeography and sea surface temperature paleothermometry reveal that the earliest throughflow of a westbound Antarctic Counter Current began ∼49–50 Ma through a southern opening of the Tasmanian Gateway. This early opening occurs in conjunction with the simultaneous onset of regional surface water and continental cooling (2–4 °C), evidenced by biomarker- and pollen-based paleothermometry. We interpret that the westbound flowing current flow across the Tasmanian Gateway resulted in cooling of Antarctic surface waters and coasts, which was conveyed to global intermediate waters through invigorated deep convection in southern high latitudes. Although atmospheric CO2 forcing alone would provide a more uniform middle Eocene cooling, the opening of the Tasmanian Gateway better explains Southern Ocean surface water and global deep ocean cooling in the apparent absence of (sub-) equatorial cooling.
So Much for the Living With Nature Myth: Earliest Lead Pollution is From North America 8,000 Years Ago
Humans began contributing to environmental lead pollution as early as 8,000 years ago, according to a University of Pittsburgh research report.
The Pitt research team detected the oldest-discovered remains of human-derived lead pollution in the world in the northernmost region of Michigan, suggesting metal pollution from mining and other human activities appeared far earlier in North America than in Europe, Asia, and South America. Their findings are highlighted on the cover of the latest issue of Environmental Science & Technology.
"Humanity's environmental legacy spans thousands of years, back to times traditionally associated with hunter-gatherers. Our records indicate that the influence of early Native Americans on the environment can be detected using lake sediments," said David Pompeani, lead author of the research paper and a PhD candidate in Pitt's Department of Geology and Planetary Science. "These findings have important implications for interpreting both the archeological record and environmental history of the upper Great Lakes."
The University of Pittsburgh research team—which included, from Pitt's Department of Geology and Planetary Science, Mark Abbott, associate professor of paleoclimatology, and Daniel Bain, assistant professor of catchment science, along with Pitt alumnus Byron A. Steinman (A&S '11G)—examined Michigan's Keweenaw Peninsula because it is the largest source of pure native copper in North America. Early surveys of the region in the 1800s identified prehistoric human mining activity in the form of such tools as hammerstones, ladders, and pit mines.
The team from the Department of Geology and Planetary Science investigated the timing, location, and magnitude of ancient copper mining pollution. Sediments were collected in June 2010 from three lakes located near ancient mine pits. They analyzed the concentration of lead, titanium, magnesium, iron, and organic matter in the collected sediment cores—finding distinct decade- to century-scale increases in lead pollution preserved from thousands of years ago.
"These data suggest that measurable levels of lead were emitted by preagricultural societies mining copper on Keweenaw Peninsula starting as early as 8,000 years ago," said Pompeani. "Collectively, these records have confirmed, for the first time, that prehistoric pollution from the Michigan Copper Districts can be detected in the sediments found in nearby lakes."
By contrast, reconstructions of metal pollution from other parts of the world, such as Asia, Europe, and South America, only provide evidence for lead pollution during the last 3,000 years, said Pompeani.
Professor Martin Richards, who heads the University's Archaeogenetics Research Group, co-authors a new article in the journal Proceedings of the National Academy of Sciences of the United States of America. It refutes a recent theory, that there is archaeological evidence for the presence of modern humans in southern Asia before the super-eruption of the Mount Toba volcano in Sumatra.
One of the most catastrophic events since humans evolved, it happened approximately 74,000 years ago. In 2005, Professor Richards led research published in an article in the journal Science which used mitochondrial DNA evidence to show that anatomically modern humans dispersed from their Africa homeland via a "southern coastal route" from the Horn and through Arabia, about 60,000 years ago – after the Toba eruption.
However, a team of archaeologists excavating in India then claimed to have found evidence that modern humans were there before the eruption – possibly as early as 120,000 years ago, much earlier than Europe or the Near East were colonised. These findings, based on the discovery of stone tools below a layer of Toba ash, were published in Science in 2007.
Now Professor Richards – working principally with the archaeologist Professor Sir Paul Mellars, of the University of Cambridge and the University of Edinburgh, with a team including Huddersfield University's Dr Martin Carr and colleagues from York and Porto – has published his rebuttal of this theory. In doing so, they have been able to draw on a much greater body of DNA evidence that was available for the earlier article.
"One of the things we didn't have in 2005 was very much evidence from India in the way of mitochondrial sequences. Now, with a lot of people doing sequencing and depositing material in databases there are about 1,000 sequences from India," said Professor Richards.
By using the mitochondrial DNA of today's populations and working backwards, and by drawing on a wide variety of other evidence and research, the team was able to make much more precise estimates for the arrival of modern humans in India.
The evidence suggests dispersal from Africa and settlement in India no earlier than 60,000 years ago.
"We also argue that close archaeological similarities between African and Indian stone-tool technologies after 70,000 years ago, as well as features such as beads and engravings, suggest that the slightly later Indian material had an African source," states Professor Richards.
"There were people in India before the Toba eruption, because there are stone tools there, but they could have been Neanderthals – or some other pre-modern population," he adds.
"The replacement of the presumably archaic humans living previously in South Asia by modern people with these new technologies appears analogous to the replacement of Neanderthals by modern humans in Europe and western Asia 50-40,000 years ago."
DIRECT IMAGING IN THE HABITABLE ZONE AND THE PROBLEM OF ORBITAL MOTION
1. Jared R. Males (a)
2. Andrew J. Skemer (a)
3. Laird M. Close (a)
a. Steward Observatory, University of Arizona, Tucson, AZ 85721, USA
High contrast imaging searches for exoplanets have been conducted on 2.4-10 m telescopes, typically at H band (1.6 μm) and used exposure times of ~1 hr to search for planets with semi-major axes of gsim 10 AU. We are beginning to plan for surveys using extreme-AO systems on the next generation of 30 m class telescopes, where we hope to begin probing the habitable zones (HZs) of nearby stars. Here we highlight a heretofore ignorable problem in direct imaging: planets orbit their stars. Under the parameters of current surveys, orbital motion is negligible over the duration of a typical observation. However, this motion is not negligible when using large diameter telescopes to observe at relatively close stellar distances (1-10 pc), over the long exposure times (10-20 hr) necessary for direct detection of older planets in the HZ. We show that this motion will limit our achievable signal-to-noise ratio and degrade observational completeness. Even on current 8 m class telescopes, orbital motion will need to be accounted for in an attempt to detect HZ planets around the nearest Sun-like stars α Cen A&B, a binary system now known to harbor at least one planet. Here we derive some basic tools for analyzing this problem, and ultimately show that the prospects are good for de-orbiting a series of shorter exposures to correct for orbital motion.
For centuries, tycoons and adventurers alike have dreamed of building a canal through Nicaragua between the Pacific and Atlantic oceans and riding a boom in international trade to new riches. Up until now, however, all comers were forced to admit defeat when faced with the sheer challenge of building a man-made river through dense, hilly jungle.
Now, the old dream is attracting a new hopeful, and this time from the other side of the world.
The Chinese company, HK Nicaragua Canal Development Investment Co. Ltd., is working with the Nicaraguan government on a massive canal project experts say could take 11 years to finish, cost $40 billion and require digging about 130 miles (200 kilometers) of waterway.
Canal proponents say the waterway could create 40,000 construction jobs and essentially double the per-capita gross domestic product of Nicaragua, one of the poorest countries in Latin America. The government plans to grant the Chinese company a concession for 100 years.
That's sparked hopes of an economic gold rush in Nicaragua, and President Daniel Ortega has pushed approval of the canal through the country's congress. Ortega presented the canal proposal Tuesday and hopes to submit it to at least an initial vote on Monday, with final approval planned by next Thursday.