segunda-feira, 24 de fevereiro de 2014

'Biggest observed meteorite impact' hits Moon

Scientists say they have observed a record-breaking impact on the Moon.

Spanish astronomers spotted a meteorite with a mass of about half a tonne crashing into the lunar surface last September.

They say the collision would have generated a flash of light so bright that it would have been visible from Earth.

The event is reported in the Monthly Notices of the Royal Astronomical Society.

"This is the largest, brightest impact we have ever observed on the Moon," said Prof Jose Madiedo, of the University of Huelva in south-western Spain.
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The impact we detected lasted over eight seconds”Prof Jose MadiedoUniversity of Huelva

The explosive strike was spotted by the Moon Impacts Detection and Analysis System (Midas) of telescopes in southern Spain on 11 September at 20:07 GMT.

"Usually lunar impacts have a very short duration - just a fraction of a second. But the impact we detected lasted over eight seconds. It was almost as bright as the Pole Star, which makes it the brightest impact event that we have recorded from Earth," said Prof Madiedo.

The researchers say a lump of rock weighing about 400kg (900lb) and travelling at 61,000km/h (38,000mph) slammed into the surface of the Moon.

They believe the dense mass, which had a width of 0.6-1.4m (2-4.6ft), hit with energy equivalent to about 15 tonnes of TNT.

This is about three times more explosive than another lunar impact spotted by Nasa last March. That space rock weighed about 40kg and was about 0.3-0.4m wide.

Scarred Moon

The team believes the impact has left behind a 40m-wide crater.

"That's the estimation we have made according to current impact models. We expect that soon Nasa could observe the crater and confirm our prediction," said Prof Madiedo.

It would be one of many scars on the lunar surface.

Unlike Earth, the Moon has no atmosphere to shield it from meteorite collisions, and its surface shows a record of every strike.

The researchers believe that impacts from rocks of about 1m in diameter could be far more common than was previously thought - both on the Moon and on Earth.

However, most rocks of this size would burn up as they entered the Earth's atmosphere, appearing as a fireball in the sky.

For meteorites to make more of an impact here, they need to be larger.

For example, the asteroid that exploded over Chelyabinsk in Russia on 15 February 2013 was estimated to be about 19m wide.

It hit the atmosphere with energy estimated to be equivalent to 500,000 tonnes of TNT, sending a shockwave twice around the globe. It caused widespread damage and injured more than 1,000 people.


quinta-feira, 20 de fevereiro de 2014

The third best place to find meteorites

Not many of us know that statistically Oman is the third best place in the world to find meteorites.
Recently the Public Knowledge Library welcomed Dr Beda A Hofmann from the Natural History Museum of Bern and Dr Edwin Gnos from the Natural History Museum of Geneva, who gave a talk on the Meteorites in Oman, providing an insight into just how special Oman was in terms of its relevance to meteorite enthusiasts and hunters.

Of 48,163 official meteorites found worldwide, 3,274 meteorites were found in Oman alone, making up 6.8 per cent of the world’s meteorites, and ranking Oman third in the number of meteorites found in the world after the Antarctica and Northwest Africa. It is also the first country on the list and the smallest territory compared to the previous two regions.

Dr Gnos opened the talk giving us a general introduction to meteorites, describing what a meteorite is and how we might recognise them, as well as where they came from, while Dr Beda A Hofmann concluded the talk with information about the Meteorite search in Oman and Statistics. I found it interesting to note that this space matter (known as a meteor before it reaches Earth) often comes from the asteroid belt but may also originate from mars, the moon or comets. It loses 90 per cent of its mass while making their way through the atmosphere.
Specific meteorites get their names based on the location they are found in and the total number of meteorites found in that place. Such as the example given by Dr Edwin Gnos, if a meteorite were to be found in Muscat (where none have been found as of yet) then it would be called Muscat001, given that it would be the first meteorite to be found specifically in Muscat.

As was explained, these meteorites are important, because “what we know about the age of the Solar System is basically from them.”
Many meteors have a dark outer later due to its journey through the atmosphere.
This plays a role in enabling their discovery against Oman’s landscape, making them more visible to the human eye. However, in time weathering will erode this outer layer and it is then more difficult to tell the difference between these space-rocks and surrounding earth rocks.
Some of us remember the issues brought to light by the media such as American meteor hunter who was jailed for two months who intended to return home with 35 meteorites he found in Oman.
While the legal situation was said to be not absolutely clear just yet, it was suggested why such action might take place. ‘Meteorites are not just rocks’ they are a glimpse at the wider universe, a fragment of the solar system, from ‘out there’ that we can study to tell us the facts that are out of this world.
However, according to the Unesco convention on the means of prohibiting and preventing the illicit import, export and transfer of ownership of cultural property, meteorites are listed as cultural property falling under the category of ‘rare collections and specimens of fauna, flora, minerals and anatomy, and objects of paleontological interest.
Currently meteors found in Oman are sent abroad to be studied. These are always listed, however, as the property of the Sultanate of Oman. More meteorite professionals are needed in Oman.
Fun facts about meteorites:
• Space matter is known as meteor until it passes through the atmosphere. Once on earth it is known as a meteorite.
• While five hundred meteorites are assumed to reach earth every year, only five or six are found by scientists to study.
• A meteorite more than ten meters in diameter is known as an asteroid.
• A meteorite less than 2 mm in diameter is known as a micrometeorite.
• A 1985 study estimated that a meteorite will hit a human once every 180 years.