Global warming linked to human migration into Europe

London, April 14 - Rising temperatures about 1.4 million years ago may have enabled the earliest humans to migrate to Europe, says a new study. 
 
The researchers from the Catalan Institution for Research and Advanced Studies (ICREA) said the spread of hominins, who were our distant human ancestors, had been halted by colder temperatures. But a warming climate 1.4 million years ago enabled them to move from Africa to Spain, and eventually across Europe, Mail Online reported on Tuesday. 
 
It is based on the analysis of the Barranco León site in the Guadix-Baza Basin in southeast Spain, where stone tools were linked to the earliest known hominins. 
 
The researchers said the early Pleistocene era (the era lasted from 2.59 million to 11,700 years ago) was characterised by colder and drier weather. "This possibly impeded the settlement of this region by the early hominin population from the southern Caucasus," the study said. 
 
But shortly afterwards, "when the climatic conditions were again favourable, a hominin presence is suddenly evidenced". 
 
The warming climate referred to in the study was on a vastly longer time scale than modern climate change. 
 
The study was led by Jordi Agusti from ICREA and its findings were published in the Journal of Human Evolution.

Comet 67P springs magnetic surprise

Vienna, April 14, 2015 - In a new twist in a landmark exploration, Europe's comet-chasing Rosetta mission has found that its target, 67P/Churyumov-Gerasimenko, has no magnetic field, scientists reported Tuesday. 
 

A robot lab sent down to Comet 67P on November 12 last year, found no evidence that its nucleus was magnetised, they said.

The finding could sweep away a key theory on the formation of comets and other solar system bodies, said researcher Hans-Ulrich Auster. 
 

It could mean that magnetic forces may not have played a role, as theorised by some, in a crucial stage of planet building.

The discovery was published in the journal Science and presented simultaneously at a meeting of the European Geosciences Union (EGU) in Vienna. 
 

It was based on measurements sent home by the washing machine-sized lab, Philae, last November.

The probe's 20-kilometre (12-mile), seven-hour descent from orbiting mothership Rosetta ended with a rough landing -- a mishap that turned out to be a boon for Auster's team.

The probe, which weighs 100 kilogrammes (220 pounds) on Earth but less than a feather in the comet's weak gravity, bounced off the hard surface several times before settling at an angle in a dark ditch. 
 

"This complex trajectory turned out to be scientifically beneficial," said a European Space Agency (ESA) statement.

"The unplanned flight across the surface actually meant we could collect precise magnetic field measurements with Philae at the four points we made contact with, and at a range of heights above the surface," said Auster. 
 

Philae had enough stored battery power for 60 hours of experiments and sent home reams of precious data before going into standby mode on November 15.

From analysis of the data, "we conclude that Comet 67P/Churyumov-Gerasimenko is a remarkably non-magnetic object," said Auster. 
 

Comets are clusters of primordial dust and ice orbiting the Sun in elliptical circuits.

The 1.3-billion-euro ($1.4-billion) Rosetta mission aims to unlock the secrets of comets, which astrophysicists believe may have "seeded" Earth with some of the ingredients for life.

Another keen area of interest is this: what comets can reveal about the role of magnetism in the formation of the solar system almost 4.6 billion years ago? 
 

The idea is that the sun, asteroids, comets, moons and planets emerged from a swirling disc of gas and dust, much of it grains of magnetite, a form of iron.

At the micro scale, magnetic fields in the protoplanetary disc helped clump material together to create embryonic bodies, according to this hypothesis. 
 

But how magnetism helped the accretion process thereafter is unclear. Some theoreticians have suggested magnetism may have played a role in the intermediary body-building phase, before the object becomes large enough -- hundreds of metres and then kilometres -- for gravity to take over as the dominant force. 
 

But Tuesday's results seem to disprove this. "The theory that magnetic forces help to build planets becomes less likely," Auster, of the Technische Universitat Braunschweig in Germany, told AFP.

"If Comet 67P/Churyumov-Gerasimenko is representative of all cometary nuclei, then we suggest that magnetic forces are unlikely to have played a role in the accumulation of planetary building blocks greater than one metre (3.25 feet) in size," he added. 
 

Karl-Heinz Glassmeier, a principal investigator on the Rosetta team, said magnetic fields appear to have been "much smaller in the early Solar System than previously thought, because if they would have been larger, we most probably would have seen a more strong magnetisation" on 67P.

Rosetta entered the comet's orbit last August after a six-billion-kilometre trek of more than a decade that required four flybys of Earth and Mars, using the planets' gravity as a slingshot to build up speed.

The comet is expected to reach its closest point to the sun, at a distance of 186 million kilometres on August 13.