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Rajasthan meteorite a rare radioactive cosmic object

Avinash Nair in Ahmedabad | August 11, 2005 10:20 IST

Elaborate tests conducted on a meteorite fragment, which fell in Rajasthan recently has revealed it to be a very rare iron meteorite showing significant radioactivity.

Tests were conducted by scientists of the Physical Research Laboratory and Basic Sciences Research Institute on the meteorite which fell at Bhuka village in Barmer district of Rajasthan on June 25, this year.

"The results of our study indicate that it is a rare iron meteorite having significant radioactivity of 54 Mn (Manganese) and 57 Co (Cobalt)," said Narendra Bhandari of BSRI.
"It seems to have orginated from the asteriodal belt between Mars and Jupiter and might have been 100 times bigger than the its present size weighing about 2.5 kilograms," the scientist said adding, tests were still to be conducted to arrive at the estimated time the body took to travel from the belt to the earth.

Also read: Object that fell from the sky was a meteorite: Scientists

The meteorite, which fell in the farm of Mubeen Sindhi with a loud cracking sound and formed a crater of about half-a-metre, is actually an alloy of iron and nickel, said Bhandari.
"It is the first iron meteorite to fall in Rajasthan among the 7 falls in the past 15 years," he said while explaining the rareness of the cosmic object.
The iron meteorite is the rarest of the three kinds of meteors, the other two being stony meteors and stony iron meteors, he said.
"Moreover, the radioactive isotopes of cobalt and manganese found together in the meteorite are also rare and is perhaps the first one to be found on earth," Bhandari added.

We were able to detect the radioactivity because the meteorite was sent to us immediately after it fell, he said, adding radioactivity slowly wanes away with the passage of time.
"About 80 per cent of most meteors entering the earth's atmosphere burn out. What makes iron meteorite rare on earth is that unlike stony meteors, they have a tendency to completely burn out," said Bhandari, who is also the president of the International Lunar Exploration Working Group.

The meteorite has a thick black crust with occasional golden or brownish tinge. The crust also has well developed regmaglypts (thumb marks formed when the metorite enters the earth's atmosphere) typical of meteorites.
"The tests conducted on a piece of the metorite sent to PRL (a large chunk was sent to the Geological Survey of India), also found it to be made of pure iron which was very different from the kind of iron found on earth which usually exists as oxides," he said.
The iron and nickel alloy, which the meteorite is made of, was formed at very high temperatures, in 'reducing atmosphere' devoid of oxygen or water before four-and-a-half billion years.

The meteorite also has a special crystalline structure which is indicative of the slow cooling process it witnessed, Bhandari said.

Since only about 126 falls have been observed all over India in the past 2 centuries, this frequency of fall (1 every 2 years) in a small area of Rajasthan anomalously high. In comparison, no more than 10 falls have been reported from the rest of India in the past 15 years, he said.

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