Ponte à Prova de Sismos

    Considerado um marco do século XXI, na Grécia, a ponte Rion-Antirion é considerada a maior ponte do mundo suspensa por cabos.

    Localizada na região Ocidental da Grécia, liga as cidades de Rion e Antirion, ligando a península do Peloponeso ao continente.

   A ponte foi projectada e construída, a fim de lidar com as condições físicas extremamente difíceis entre aquelas duas cidades. Profundidade elevada de água, camadas de solo fraco, actividade sísmica intensa, ventos fortes e deslocamentos numa das falhas mais activas da Europa são algumas das dificuldades que construtores e projectistas tiveram de ultrapassar, e que se explicam neste Documentário da National Geographic.

   Devido ao carácter inovador desta estrutura o projecto foi premiado com nove distinções pela comunidade científica internacional.

    Pode ler mais sobre o projecto aqui.

A ponte Rion-Antirion, ligando o Peloponeso ao continente (Wikipedia)

Massive Dinosaur Fossil Unearthed by Pipeline Installation Crew

A large dinosaur fossil has been found by a pipeline installation crew, during the works, on Southwest of Spirit River, Alberta (province of Canada).

View of the dinosaur fossil that was found.

Grutas Misteriosas de Guangxi

"Grutas Misteriosas de Guangxi" é o nome do programa que a National Geographic Channel irá transmitir no dia 4 de Novembro às 22h30.

Guangxi é uma pequena zona na China, onde dominam grutas profundas e tão grandes que albergam florestas e vasta e pouco exploradas.
Na China são conhecidas como Tiankeng, que significa "Abismo Divino". São contabilizadas menos de 100 em todo o mundo, e quase todas podem ser encontradas neste local.

Grutas em Guangxi

O documentário, conta com o professor Darryl Granger a liderar um equipa de espedição internacional, onde, centenas de metros abaixo da superfície da Terra têm como objectivo descobrir como se formam estas enormes grutas e o porquê da sua localização.

Life on Earth Began on Land, Not in Sea?

First cells likely arose in steamy mud pots, study suggests.

Steam rises from geothermal plains in Kamchatka, Russia.

Photograph by Michael Melford, National Geographic

Dave Mosher

for National Geographic News

Published February 13, 2012

Earth's first cellular life probably arose in vats of warm, slimy mud fed by volcanically heated steam—and not in primordial oceans, scientists say.

(Also see "All Species Evolved From Single Cell, Study Finds.")

The concept, based on the latest cellular and geologic research, resembles a suggestion by famed naturalist Charles Darwin that life could have sprung from a "warm little pond" rich in nutrients.

(Find out about Darwin's scientific inspirations in National Geographic magazine.)

Despite this early musing by Darwin, marine-origin theories for life have been popular in recent years, because oceanographers continue to find oases of life thriving on the seafloor.
In these deepwater ecosystems, simple yet hardy microbes munch on noxious minerals spewing from hot volcanic vents—a setting many experts think could resemble the birthplace of the first cells.

(Related pictures: "'Lost World' of Odd Species Found Off Antarctica.")

But in the new study, researchers argue that the fluid all cells struggle to keep within their thin cellular membranes couldn't be more dissimilar to ancient ocean water.
Instead, the team discovered, this cellular fluid is very similar to condensed vapors found in volcanic mud pots on land.
Such terrestrial environments boast the high ratios of potassium to sodium found in all living cells. Marine environments, meanwhile, are far too rich in sodium.
"For cells to synthesize proteins—their molecular machines—they need a lot of potassium. Sodium blocks these activities," said study co-author Armen Mulkidjanian, a biophysicist at the University of Osnabrück in Germany.
"Life cannot live without synthesizing proteins, so it must keep potassium high."

Keep It Simple, Cells

Cells today rely on complex proteins to pump excess sodium out through their membranes, so the cells can function properly.
The first cells, however, had no such machinery at their disposal—just rudimentary cellular membranes and whatever nutrients the cells were lucky enough to trap inside.
As a result, the first cells were highly permeable and completely at the mercy of their environments. The ratio of potassium to sodium therefore had to be greater than one to one, in favor of potassium.
But in ancient seawater—as well as in modern seawater—sodium outnumbers potassium 40 to 1.
With this hurdle in mind, Mulkidjanian and his colleagues enlisted the help of geologists to understand where else life might have originated between 4.3 and 3.8 billion years ago.

(Related: "Life Ingredients Found in Superhot Meteorites—A First.")

The team realized that geothermal fields on land could do the job, particularly the mud pots found in places such as Yellowstone National Park.
"Mud pots are where steam is coming out of the earth and condensing, carrying with it many minerals, including potassium," Mulkidjanian said. "They look like slime coming out of the earth and would make a nice kind of hatchery for the first cells."
Scientists had long ignored mud pots as possible analogs to primordial ooze, because the modern-day versions are swimming in sulfuric acid, a deadly chemical that forms when hydrogen sulfide encounters oxygen in the atmosphere.

(Related: "Space Poison Helped Start Life on Earth?")

"People were scared away by the acidic condition, but Earth used to have very little oxygen in its atmosphere," Mulkidjanian said.
"These anoxic environments were stable over millions of years and were probably conducive to supporting the first life on Earth."

The new study arguing that life started on land was published online today by the Proceedings of the National Academy of Sciences.

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Retirado de:

http://news.nationalgeographic.com/news/2012/02/120213-first-life-land-mud-darwin-evolution-animals-science/

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National Geographic - Mass Extinctions

More than 90 percent of all organisms that have ever lived on Earth are extinct. As new species evolve to fit ever changing ecological niches, older species fade away. But the rate of extinction is far from constant. At least a handful of times in the last 500 million years, 50 to more than 90 percent of all species on Earth have disappeared in a geological blink of the eye.

Though these mass extinctions are deadly events, they open up the planet for new life-forms to emerge. Dinosaurs appeared after one of the biggest mass extinction events on Earth, the Permian-Triassic extinction about 250 million years ago. The most studied mass extinction, between the Cretaceous and Paleogene periods about 65 million years ago, killed off the dinosaurs and made room for mammals to rapidly diversify and evolve.

The causes of these mass extinction events are unsolved mysteries, though volcanic eruptions and the impacts of large asteroids or comets are prime suspects in many of the cases. Both would eject tons of debris into the atmosphere, darkening the skies for at least months on end. Starved of sunlight, plants and plant-eating creatures would quickly die. Space rocks and volcanoes could also unleash toxic and heat-trapping gases that—once the dust settled—enable runaway global warming.

An extraterrestrial impact is most closely linked to the Cretaceous extinction event. A huge crater off Mexico's Yucatán Peninsula is dated to about 65 million years ago, coinciding with the extinction. Global warming fueled by volcanic eruptions at the Deccan Flats in India may also have aggravated the event. Whatever the cause, dinosaurs, as well as about half of all species on the planet, went extinct.

Massive floods of lava erupting from the central Atlantic magmatic province about 200 million years ago may explain the Triassic-Jurassic extinction. About 20 percent of all marine families went extinct, as well as most mammal-like creatures, many large amphibians, and all non-dinosaur archosaurs. An asteroid impact is another possible cause of the extinction, though a telltale crater has yet to be found.

Largest Ever Die-Off

The Permian-Triassic extinction event about 250 million years ago was the deadliest: More than 90 percent of all species perished. Many scientists believe an asteroid or comet triggered the massive die-off, but, again, no crater has been found. Another strong contender is flood volcanism from the Siberian Traps, a large igneous province in Russia. Impact-triggered volcanism is yet another possibility.

Starting about 360 million years ago, a drawn-out event eliminated about 70 percent of all marine species from Earth over a span of perhaps 20 million years. Pulses, each lasting 100,000 to 300,000 years, are noted within the larger late Devonian extinction. Insects, plants, and the first proto-amphibians were on land by then, though the extinctions dealt landlubbers a severe setback.

The Ordovician-Silurian extinction, about 440 million years ago, involved massive glaciations that locked up much of the world's water as ice and caused sea levels to drop precipitously. The event took its hardest toll on marine organisms such as shelled brachiopods, eel-like conodonts, and the trilobites.

Happening Now?

Today, many scientists think the evidence indicates a sixth mass extinction is under way. The blame for this one, perhaps the fastest in Earth's history, falls firmly on the shoulders of humans. By the year 2100, human activities such as pollution, land clearing, and overfishing may have driven more than half of the world's marine and land species to extinction.

Fonte: http://science.nationalgeographic.com