MOSCOW, November 10 (Itar-Tass) - The meteorite threat is becoming more acute because the density of population on Earth is constantly growing, Olga Popova, a senior research fellow of the Institute of Geosphere Dynamics of the Russian Academy of Sciences, told Itar-Tass.

Popova led an expedition that studied the impacts of the meteorite shower that hit Russia’s Chelyabinsk region in the Urals in February. The expedition visited more than 50 settlements around Chelyabinsk, interrogated dozens of eyewitnesses and conducted astronomic survey. Of great help, according to Popova, were video recordings handed over by witnesses.

Scientists have arrived at the conclusion that the February meteorites were fragments of a small asteroid (or a meteoroid), which had a diameter of up to 20 meters and a weight of about 11,000 tonnes when it entered the Earth’s dense atmosphere at a velocity of 19 kilometres a second. The object’s energy was about 0.5 megatonnes of TNT.

“It was clear from the very beginning, from the very first recordings that this object was a meteorite,” she said. “A big celestial object entered the atmosphere, broke into fragments there and its pieces fell down to the Earth.” The biggest fragment weighing more than 600 kilograms was lifted from the bottom of Lake Chebarkul in October.

According to scientists, a large number of small particles of the space origin get into the Earth’s atmosphere every day. From ten to 30 celestial objects with a diameter of about one metre enter the atmosphere annually, but big objects are rather rare. “The Tunguska meteorite of 1908 is believed to be bigger,” Popova noted. “Its energy is estimated in a arnge from three to 15 megatonnes.”

An 11,000-tonne meteorite with a diameter of about 20 meters entered the Earth atmosphere on February 15, 2013 and broke into numerous fragments, the bulk of which fell down in Russia’s Urals Chelyabinsk region. A shock wave that followed the fall of the meteorite broke windows in more than 4,700 houses in Chelyabinsk. Astronomers say the Chelyabinsk meteorite was the biggest celestial object to hit the Earth since the Tunguska event in 1908, when a huge meteorite exploded over Russia’s Siberia. This time, the meteorite shower was observed in five Russian regions - the Tyumen, Sverdlovsk, Chelyabinsk and Kurgan regions, and in the republic of Bashkortostan.

Eyewitnesses said they had first seen a bright flash in the sky and had heard the sound of explosion. More than 1,500 people, including more than 300 children, sought medical help after the incident, and as many as 69 people, including 13 children, were hospitalized.

Fragments of this meteorite are now being studied by scientists.