Saturday, July 13, 2013

Russian Chelyabinsk meteorite pieces go under microscope


SEM of Chelyabinsk meteor fragment  
Often referred to as the Chebarkul meteorite after the lake where many pieces were found, the space rock appears to be a standard "chondrite"
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Scientists have released microscopic images of fragments of the meteorite that hit central Russia in February.
A team from the Ural Federal University was able to analyse some of the dozens of samples as soon as they were found.
But the technique they used allowed them to assess the rock's chemical make-up at the microscopic level even as they snapped pictures of the fragments.
This will provide extra information on the space rock's formation and journey.
The fragments represent just a small portion of the remains of the 17m-diameter body that struck the Earth's atmosphere in a spectacular trail of light over the city of Chelyabinsk.
The team, led by Urals Federal University's Viktor Grokhovsky, determined right away that the overall chemistry of the meteorite was a familiar "chondrite".
"The fragments contain a standard number of minerals, including olivine, pyroxene, troilite and kamacite. These minerals that can be discovered only in outer space confirm the fragments' extraterrestrial nature," he told the Voice of Russia at the time.
But far more information was in the offing.
SEM of Chelyabinsk meteor fragment  
The way differing minerals are laid out gives clues as to their origin and their journey
The team was using a scanning electron microscope, which fires a beam of electrons focused onto a tiny part of a sample, scanning around to see how the electrons are deflected and thereby building up a detailed picture of the sample's nanometre-scale bumps and valleys.
But that process causes the emission of a small amount of X-ray radiation - with the exact energy of the X-rays corresponding to the chemical element present in the focus of the electron beam.
This is where a silicon drift detector comes in - harvesting these X-rays and determining their energy. The result is a series of what are called X-ray maps - pictures of the same sample showing the presence and quantity of different elements.
It is this understanding of the minerals at a microscopic level that goes far beyond simply telling us what the meteorite is made of, said Simon Burgess of Oxford Instruments, which made the X-max silicon drift detector used by the team.
"For the researchers who are looking at this meteorite, it's going to be telling them information about which (mineral) phase is associated with which," he told BBC News.
"When they get into more detail beyond what the main chemistry of the meteorite is, they may be looking at processes in terms of how it formed, the temperature it formed at, what its history has been since its formation, possibly things about what happened to it during its impact with the Earth.
"A lot of that you cannot tell just by crushing it up and getting a 'bulk analysis'; you have to look at the chemistry of the individual parts and associations between the different minerals in the meteorite."
The X-max technology is in the running for the Royal Academy of Engineering's MacRobert Award, to be announced on Friday 19 July.
Composite image of X-max images 
 The X-ray maps show the precise distribution of individual chemical elements

Typhoon Soulik makes landfall in Taiwan


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Cindy Sui in Taipei says officials are still assessing the extent of the damage
Typhoon Soulik has made landfall in Taiwan, bringing strong winds and torrential rain to the island.
So far one person is reported to have died while 21 have been injured in the extreme weather.
More than 8,500 people have been evacuated from mountainous and other dangerous areas and thousands of soldiers have been deployed.
Soulik is set to arrive in mainland China's eastern provinces of Fujian and Zhejiang later on Saturday.
Local authorities there have been asked to implement emergency response plans, China's state-run news agency Xinhua reported, after recent torrential rain across large parts of the country reportedly left 200 people dead or missing.
Uprooted trees Typhoon Soulik, a medium-force typhoon, had wind speeds of around 173 km/h (100 mph) on Saturday morning.
It made landfall at around 03:00 on Saturday (19:00 GMT on Friday), Taiwan's Central Weather Bureau reported.
A police officer was killed by falling bricks but other people suffered mostly light injuries, including from fallen trees or being blown off their scooters.
The strong winds and heavy rain have caused electricity disruptions, a run on food and essential supplies in supermarkets, and uprooted trees and signs in some areas.
This typhoon is the first to hit Taiwan this year and there had been fears of major damage because the island was the first place it made landfall, reports the BBC's Cindy Sui in the capital Taipei.
Nearly 50,000 soldiers have been put on standby, she says.
Schools and offices in Taipei and several other cities had closed on Friday afternoon as the tropical storm neared.
Map showing Taiwan and the Chinese provinces of Fujian and Zhejiang
Some flights to Taiwan have been disrupted, with both Cathay Pacific and China Airlines announcing cancellations.
Precautionary measures have been taken to close the roads and bridges along areas most susceptible to disaster, officials said.
Fishing boats had been returned to the shore before the typhoon hit, and members of the public were urged to avoid mountain and coastal areas.
Evacuated residents - including 3,000 from Kaohsiung city and 2,000 from Pingtung county in the south of Taiwan - have been taken to local government buildings that have been turned into shelters, Agence France Presse reported.
More than 2,000 tourists had earlier been evacuated from Taiwan's Green Island, near the city of Taitung, as a precaution.
Typhoons are common during the summer in parts of East Asia, where the warm moist air and low pressure conditions enable tropical cyclones to form.
In 2009, Taiwan was hit by Typhoon Morakot, which left hundreds dead in floods and mudslides.