Extreme Temperatures Blamed for 'Dead Zone'

 

Scientists have discovered why the 'broken world' following the worst extinction of all time lasted so long -- it was simply too hot to survive.

The end-Permian mass extinction, which occurred around 250 million years ago in the pre-dinosaur era, wiped out nearly all the world's species. Typically, a mass extinction is followed by a 'dead zone' during which new species are not seen for tens of thousands of years. In this case, the dead zone, during the Early Triassic period which followed, lasted for a perplexingly long period: five million years.

A study jointly led by the University of Leeds and China University of Geosciences (Wuhan), in collaboration with the University of Erlangen-Nurnburg (Germany), shows the cause of this lengthy devastation was a temperature rise to lethal levels in the tropics: around 50-60°C on land, and 40°C at the sea-surface.

Lead author Yadong Sun, who is based in Leeds while completing a joint PhD in geology, says: "Global warming has long been linked to the end-Permian mass extinction, but this study is the first to show extreme temperatures kept life from re-starting in Equatorial latitudes for millions of years."

It is also the first study to show water temperatures close to the ocean's surface can reach 40°C -- a near-lethal value at which marine life dies and photosynthesis stops. Until now, climate modellers have assumed sea-surface temperatures cannot surpass 30°C. The findings may help us understand future climate change patterns.

The dead zone would have been a strange world -- very wet in the tropics but with almost nothing growing. No forests grew, only shrubs and ferns. No fish or marine reptiles were to be found in the tropics, only shellfish, and virtually no land animals existed because their high metabolic rate made it impossible to deal with the extreme temperatures. Only the polar regions provided a refuge from the baking heat.

Before the end-Permian mass extinction, Earth had teemed with plants and animals including primitive reptiles and amphibians, and a wide variety of sea creatures including coral and sea lillies.

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Radar helps solve painted lady migration mystery

The mystery of an annual disappearance of a UK butterfly has been solved, scientists say after tracking the painted lady's migration on radar.

They found that the butterflies do not die in this country at the end of summer, as some believed, but make a high altitude escape south - one leg of a 9,000-mile migration.

The team analysed 60,000 sightings from British observers for the study.

The discoveries are "astonishing", says Richard Fox, a co-author on the paper.

The findings are based on data from 2009 and published in the journal Ecography.

It was known that painted ladies come to the UK from Europe to breed. But this study is the first to explain where the butterflies go as the cold weather approaches later in the year, said Richard Fox, surveys manager for Butterfly Conservation.

"The question was why don't we see them? We see birds migrating southwards, we see red admiral butterflies migrating southwards which are really close relatives of painted ladies. So the fact that we're not seeing painted ladies going southwards, does that mean they're not doing it?"

"The radar element of this study has given us an answer to that," Mr Fox told BBC Nature.

"They are going southwards but they're doing it out of human eyesight, up in the sky."

The butterflies travelled at altitudes of over 1,000m but would descend to benefit from favourable winds, the study found.

The findings debunk one theory, called the "Pied Piper hypothesis". That suggests that painted ladies come to UK to "just sit around in Britain hoping that it's the promised land and suddenly find winter comes and they all die", according to Mr Fox.

"The apparent lack of a return migration of the late-summer generation of painted lady butterflies was one of the greatest enigmas in insect migration ecology," said Dr Jason Chapman, a researcher at Rothamsted Research, Hampshire, the longest running agricultural research station in the world.

"But through a combination of traditional monitoring by butterfly enthusiasts and new radar techniques we have finally solved this long-standing puzzle," he said.

Curiosity Discovers Ancient Streambed on Mars

NASA’s Curiosity rover has captured images of bedrock that suggest a fast-moving stream once flowed on the Martian surface.

“From the size of gravels it carried, we can interpret the water was moving about 3 feet per second, with a depth somewhere between ankle and hip deep,” explained Curiosity science co-investigator Dr William Dietrich of the University of California in Berkeley.

“Plenty of papers have been written about channels on Mars with many different hypotheses about the flows in them. This is the first time we’re actually seeing water-transported gravel on Mars. This is a transition from speculation about the size of streambed material to direct observation of it,” Dr Dietrich said according to science news. com website.

The site lies between the north rim of Gale Crater and the base of Mount Sharp, a mountain inside the crater. Earlier imaging of the region from Mars orbit allows for additional interpretation of the gravel-bearing conglomerate. The imagery shows an alluvial fan of material washed down from the rim, streaked by many apparent channels, sitting uphill of the new finds.

The rounded shape of some stones in the conglomerate indicates long-distance transport from above the rim, where a channel named Peace Vallis feeds into the alluvial fan. The abundance of channels in the fan between the rim and conglomerate suggests flows continued or repeated over a long time, not just once or for a few years.

The discovery comes from examining two outcrops, called ‘Hottah’ and ‘Link,’ with the telephoto capability of Curiosity’s mast camera. Those observations followed up on earlier hints from another outcrop, which was exposed by thruster exhaust as Curiosity, the Mars Science Laboratory Project’s rover, touched down.