Asteroid will come closer than satellites – but it's not the end of the world

Lump of rock 50 metres long will soar through sky at about 8 miles a second

Anyone happening to glance towards the heavens in a week's time and glimpses a 50-metre-long lump of rock hurtling ominously through the skies need not panic.

Although it will pass closer to us than any asteroid has for the past 15 years – closer even than the TV satellites that girdle the planet – NASA insists that 2012 DA14 will miss Earth by a good 17,100 miles (27,520km).

"No Earth impact is possible," said Donald Yeomans, an astronomer with the US space agency.

He also pointed out that the planet was bombarded by about 100 tonnes of space material every day.

"Basketball-sized objects come in daily," he said. "Volkswagen-sized objects come in every couple of weeks. As you get to larger and larger sizes the number of objects out there is less and less, so the frequency of hits goes down."

Yeomans added that asteroids as big as DA14, which is abou t 46 metres wide, are estimated to strike Earth about every 1,200 years.

"For objects of this size, this is the closest predicted encounter that we're aware of," he said.

The asteroid's closest approach will be at 7.24pm on 15 February, meaning that those gazing keenly at the dark skies of eastern Europe, Asia and Australia will stand the best chance of seeing it through telescopes or binoculars.

DA14, which was discovered last year by a group of amateur astronomers in Spain, will soar through the sky at about 8 miles a second. At that speed, an object of similar size on a collision course with Earth would strike with the force of about 2.4m tonnes of dynamite.

The last time that happened was in 1908 when an asteroid or comet exploded over Siberia, levelling 80m trees over 830sq miles.

"Although they wouldn't cause a global catastrophe if they impact the Earth, they still do a lot of regional destruction," said Lindley Johnson, who oversees the Near-Earth Object Observations Programme at Nasa headquarters in Washington DC.

NASA  finds and tracks all near-Earth objects that are 1km or larger in diameter. Their efforts are intended to give scientists and engineers as early a warning as possible so that steps can be taken to avert the kind of catastrophe that did for the dinosaurs.

About 66m years ago, a six-mile-wide object smashed into the Yucatán peninsula in Mexico, leading to the demise of not just the giant lizards, but also most of the plant and animal life on Earth.

Source: the Guardian

B.N

Ozone Thinning Has Changed Ocean Circulation

 

 

 

A hole in the Antarctic ozone layer has changed the way that waters in the southern oceans mix, a situation that has the potential to alter the amount of CO2 in the atmosphere and eventually could have an impact on global climate change, a Johns Hopkins earth scientist says.

In a paper published in this week's issue of the journal Science, Darryn W. Waugh and his team show that subtropical intermediate waters in the southern oceans have become "younger" as the upwelling, circumpolar waters have gotten "older" -- changes that are consistent with the fact that surface winds have strengthened as the ozone layer has thinned,according to Science Daily.

"This may sound entirely academic, but believe me, it's not," said Waugh, of the Morton K. Blaustein Department of Earth and Planetary Sciences at Johns Hopkins' Krieger School of Arts and Sciences. "This matters because the southern oceans play an important role in the uptake of heat and carbon dioxide, so any changes in southern ocean circulation have the potential to change the global climate."

Waugh's team used measurements taken from the early 1990s to the mid-to-late 2000s of the amount of a chemical compound known as "chlorofluorocarbon-12," or CFC-12, in the southern oceans. CFC-12 was first produced commercially in the 1930s and its concentration in the atmosphere increased rapidly until the 1990s when it was phased out by the Montreal Protocol on substances that deplete the ozone layer. (Prior to the Montreal Protocol, CFC-12 was used in products such as aerosol hairsprays and refrigerants and in air conditioning systems.

From those ocean measurements, Waugh's team was able to infer changes in how rapidly surface waters have mixed into the depths of the southern oceans. Because they knew that concentrations of CFCs at the ocean surface increased in tandem with those in the atmosphere, they were able to surmise that the higher the concentration of CFC-12 deeper in the ocean, the more recently those waters were at the surface.

The inferred age changes -- "younger" in the subtropics, "older" nearer the South Pole -- are consistent with the observed intensification of surface westerly winds, which have occurred primarily because of the Antarctic ozone hole, suggesting that stratospheric ozone depletion is the primary cause of the changes in ocean ventilation. As stratospheric ozone recovers over the next 50 years, the changes in ventilation may slow or reverse. The impact of continued increases in greenhouse gases in the atmosphere will also need to be considered, however. The combined impact of the two factors on the southern oceans' ventilation and uptake of heat and carbon is an open question.

R.S

 

 

 

Seminar on Combating Desertification

DAMASCUS, (ST) - A seminar entitled "hand in hand to combat desertification" was held here and  discussed the role of traditional practices in agriculture in increasing desertification, land deterioration, the impact of the use of wastewater for irrigation and the role of guidance in agricultural work.

At the opening ceremony held by the Ministry of Environment in cooperation with the General Federation of Peasants (GFP), Deputy Minister of Environment Affairs, eng. Imad Hassoun, confirmed the importance of teamwork to rebalance the environmental systems and focus on raising awareness about the aggravated risks concerning the desertification issue, noting that the government has exerted great efforts to reduce land deterioration and combating desertification .

 "The Ministry of Environment completed the National Plan to combat desertification, which included many of the projects that have been listed in the fifth plan, including integrated development of pastures and livestock, partnership development project in local communities in the Badia, the of project of the traditional water management techniques  and the use of renewable energy," eng. Hassoun pointed out.
For his part, Head of the Agricultural Affairs Bureau at the GFP, Ali Habib Issa, clarified that the importance of working together to preserve the environment and the need to educate farmers and the people about the problem of desertification by doing initiatives to make people more aware of this vital issue and the need to circulate this experience on the Syrian governorates.

 Sh. Kh.

Sockeye salmon 'sense magnetic field of home'

Salmon use the Earth's magnetic field to navigate across the ocean as they return to their home rivers to breed, research suggests.

Each year millions of fish make the journey home in one of the toughest migrations of the animal kingdom.

The memory of the magnetic field where they first entered the sea helps them find their way back, say US scientists,according to BBC.

The data, in Current Biology, provide the first direct evidence that salmon use geomagnetic cues in migration.

Other marine animals, including turtles and seals, may also use the same homing mechanism, say researchers.

The journey of adult sockeye salmon from the northern Pacific Ocean back to the individual freshwater rivers of their birth is one of the toughest migrations of all animals.

There are several theories for how salmon locate their nurseries after spending years out at sea.

One hypothesis, known as natal homing, is that salmon use both chemical and geomagnetic cues to find their way home.

In order to test the theory, researchers studied fisheries data spanning 56 years charting the return of salmon to the Fraser River in British Columbia.

The route the fish chose to swim around Vancouver Island matched the intensity of the geomagnetic field near their home rivers.

 Sockeye salmon live in the northern Pacific Ocean, but breed in freshwater

  After spending several years in the ocean reaching sexual maturity, they return to the freshwater rivers in which they were born during the summer months

 During spawning, each female lays 2,000 eggs, before both the males and females die

 Young salmon mature in the freshwater nurseries, and at two years of age they depart for the open ocean

Nathan Putman, a researcher at Oregon State University, told BBC News: "For salmon to find their way back home, they remember the magnetic field that exists where they first enter the sea as juveniles, and once they reach maturity, they seek that same coastal location, with the same magnetic field.

 "In other words, salmon remember the magnetic field where they enter the ocean and come back to that same spot once they reach maturity."

Sea turtles, elephant seals and many other fish, including eels, tuna and sturgeon, have a similar migratory strategy, he added.

James J Anderson and Chloe Bracis of the University of Washington say the work supports recent modelling studies showing geomagnetic imprinting is feasible to return salmon to their home river. It also complements laboratory findings that trout olfactory systems can detect geomagnetic fields.

M.Wassouf

Vegetation Changes in Cradle of Humanity: Study Raises Questions About Impact On Human Evolution

The bipedal human ancestor or the grassland encroaching on the forest? A new analysis of the past 12 million years' of vegetation change in the cradle of humanity is challenging long-held beliefs about the world in which our ancestors took shape -- and, by extension, the impact it had on them.

The research combines sediment core studies of the waxy molecules from plant leaves with pollen analysis, yielding data of unprecedented scope and detail on what types of vegetation dominated the landscape surrounding the African Rift Valley (including present-day Kenya, Somalia and Ethiopia), where early hominin fossils trace the history of human evolution,according to Science Daily.

"It is the combination of evidence both molecular and pollen evidence that allows us to say just how long we've seen Serengeti-type open grasslands," said Sarah J. Feakins, assistant professor of Earth sciences at the USC Dornsife College of Letters, Arts and Sciences and lead author of the study, which was published online in Geology on Jan. 17.

Feakins worked with USC graduate student Hannah M. Liddy, USC undergraduate student AlexaSieracki, Naomi E. Levin of Johns Hopkins University, Timothy I. Eglinton of the EidgenössischeTechnischeHochschule and RaymondeBonnefille of the Universitéd'Aix-Marseille.

The role that the environment played in the evolution of hominines -- the tribe of human and ape ancestors whose family tree split from the ancestors of chimpanzees and bonobos about 6 million years ago -- has been the subject of a century-long debate.

Among other things, one theory dating back to 1925 posits that early human ancestors developed bipedalism as a response to savannas encroaching on shrinking forests in northeast Africa. With fewer trees to swing from, human ancestors began walking to get around.

While the shift to bipedalism appears to have occurred somewhere between 6 and 4 million years ago, Feakins' study finds that thick rainforests had already disappeared by that point -- replaced by grasslands and seasonally dry forests some time before 12 million years ago.

In addition, the tropical C4-type grasses and shrubs of the modern African savannah began to dominate the landscape earlier than thought, replacing C3-type grasses that were better suited to a wetter environment. (The classification of C4 versus C3 refers to the manner of photosynthesis each type of plant utilizes). While earlier studies on vegetation change through this period relied on the analysis of individual sites throughout the Rift Valley -- offering narrow snapshots -- Feakins took a look at the whole picture by using a sediment core taken in the Gulf of Aden, where winds funnel and deposit sediment from the entire region. She then cross-referenced her findings with Levin who compiled data from ancient soil samples collected throughout eastern Africa.

"The combination of marine and terrestrial data enable us to link the environmental record at specific fossil sites to regional ecological and climate change," Levin said.

R.S