The Chebarkul Meteor of 15 February 2013

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1 The Chebarkul Meteor of 15 February 2013 Introduction The earth has long been bombarded by objects from space that range from microscopic sized particles to objects tens of kilometres or larger. Fortunately, impacts with the larger objects are rare. These objects are mostly asteroids, which are metallic, rocky bodies, without atmospheres, that orbit the Sun, just like planets, but are too small to be considered planets themselves. There are tens of thousands of them gathered into the main asteroid belt, a donut-shaped ring located between the orbits of Mars and Jupiter. Astronomers conclude they are made from primordial rock. Jupiter's strong gravity prevented these small bodies from forming into a planet when the solar system began 4.6 billion years ago. In November 2007, NASA reported 900 known potentially hazardous objects (PHOs), most of which are asteroids. PHOs are defined as objects larger than 492 feet in diameter whose trajectories bring them to within about 4.6 million miles of the Earth s orbit. NASA scientists estimate the total population of PHOs to be around 20,000. A tsunami can be generated by an asteroid impacting the ocean. There are no known examples during human history of tsunami being generated by asteroids, although the earth does preserve geological evidence of ocean impacts from asteroid-tsunami. For example, there is evidence to suggest that a 1 km or larger object, the Eltanin asteroid, impacted the Southern Ocean about 2.15 million years ago. This event is estimated to have generated a tsunami with amplitudes between about 10 and 20 metres along the NSW coast. The catastrophic K/T impact event that ended the Cretaceous period about 65 million years ago is attributed to an asteroid, likely larger than 10 km, impacting the area near Chicxulub, Mexico. This event generated a huge tsunami in the Gulf of Mexico and Caribbean Sea, generating asteroid-tsunami deposits in Texas, Haiti and Florida. Objects less than 30 metres in dimension disintegrate as they enter the earth s atmosphere, and are therefore unlikely to be able to generate ground impacts or tsunami. Moderate sized objects ( metres in diameter) are expected to contribute most of the hazard due to their relatively frequent occurrence. Objects larger than this would generate global catastrophes that would engulf the entire coastlines of affected continents if they impacted the ocean, but the recurrence intervals of such events are very long. The Chebarkul Meteor of 15 February 2013 On Friday, February 15, a meteor exploded over the city of Chelyabinsk (population: 1 million) around 9.20am local time (3:20: 26 UTC) in Russia's central Ural Mountains. The shockwave from the blinding fireball injured 1,200 people and damaged thousands buildings in six. Scientists at the US space agency NASA estimated that the amount of energy released in the atmosphere was about 30 times greater than that of the nuclear bomb dropped on the Japanese city of Hiroshima during World War II. NASA stated that an event of this magnitude is expected to occur on average once every 100 years. Risk Frontiers Briefing Note 249 page 1

2 Figure 1 - The meteor as it approaches Earth. Image Credit: AP/Nasha Gazeta Figure 2 - Meteor impact area in Chelyabinsk. Image credit: Google Earth, NASA/JPL-Caltech. Risk Frontiers Briefing Note 249 page 2

Unrelated to the 2012 DA14 asteroid flyby The meteor hit just as the world braced for a close encounter with a large asteroid that was to pass by earth, as close at 17,150 miles.

3 Unrelated to the 2012 DA14 asteroid flyby The meteor hit just as the world braced for a close encounter with a large asteroid that was to pass by earth, as close at 17,150 miles. Reaching a width of 150 feet (~46 metres) the 2012 DA14 asteroid is one of the largest known asteroids to approach the planet. According to the European Space Agency there is no connection between the asteroid and the meteor that hit Russia. NASA stated that the trajectory of the Russia meteor was significantly different from the trajectory of asteroid 2012 DA14, making it a completely unrelated object. DA14 was not expected to be perceptible to the naked eye, though it was expected to be visible from Asia, Eastern Europe and Australia with the aid of binoculars. On average, objects of this size pass this close to Earth once every 40 years, and strike the planet once every 1,200 years. The last time an object of a size similar to DA14 hit the earth was also in Russia, and is known as the Tunguska event. In June 1908, the asteroid, which was estimated at 100 meters in diameter, burst in the air over the Podkamennaya Tunguska River, in Russia s Krasnoyarsk Krai region. It was the largest such hit in recorded history. A description of its impact is described further below and in Risk Frontiers Briefing Note 161, July Figure 3 - A graphic comparing the Russian meteor with the 2012 DA14 asteroid. Note some measurements have since been updated (National Post). Risk Frontiers Briefing Note 249 page 3

4 Size and fragments of the Chebarkul Meteor Reports from NASA state that the estimated size of the meteor that hit Russia on Friday, prior to entering Earth's atmosphere, has been revised to 55 feet (17 metres), and its estimated mass has increased to 10,000 tons. The infrasound data indicates that the event, from atmospheric entry to the meteor's airborne disintegration took 32.5 seconds. The meteor was travelling at 46,000 mph when it hit the Earth's atmosphere and exploded, according to new data from Paul Abell at the Johnson Space Center. It exploded in the atmosphere because its composition is stony, rather than metallic, like the meteor that left a massive crater in Arizona, Abell said. Over the weekend, scientists collected 53 tiny pieces of dark porous material that were recovered by local residents near Chebarkul Lake, 100 kilometres west of Chelyabinsk. The biggest piece was 7 millimetres long. The meteorite pieces collected by scientists were described as bits of a chondrite, a type of stony meteorite. They contain at least 10 per cent metallic iron and nickel alloy as well as chrysolite and sulfite. Scientists plan to search the lake again for larger pieces of the meteorite and if found plan to name the meteorite Chebarkul, after the lake. Not everyone who has found pieces is turning them in, however. Apparently some enterprising locals were offering what they claimed to be fresh meteorite pieces for sale online for as much as $10,000 apiece. This has sparked a "meteorite rush" around the industrial city of Chelyabinsk. Damage Building Most of the damage was caused by the shock waves as the meteor broke up in the atmosphere. The force of the explosion was enough to shatter dishes, televisions, and windows. The explosion is estimated to have shattered more than 1 million square feet of glass. Preliminary reports suggest that more than 3,000 homes and businesses sustained damage from broken glass and cracked walls, including regular households, hospitals, schools and a zinc factory where part of the roof collapsed. It has been reported that 30 per cent of the windows shattered by shockwaves that rocked that part of the country, where temperatures on Saturday dipped to -20C, have already been repaired. The remaining windows will be repaired over the next week, except for some large ones built in the Soviet era that will require weeks to fix. The building most seriously damaged by the shockwaves was the Chelyabinsk ice rink. Injuries The unpredicted meteor strike ground traffic to a halt in the industrial city of Chelyabinsk as residents poured out on the streets to watch the light show before hovering for safety when a sonic boom rang out directly overhead. Local authorities estimate that 1200 people were injured, most of them by flying glass. Authorities cancelled school and asked residents to stay indoors. Doctors said some Risk Frontiers Briefing Note 249 page 4

5 sustained more serious wounds from doors that were blasted off hinges and ceiling collapses. About 50 people were recovering in hospitals early Saturday. Insurance In many countries with developed insurance markets, a comprehensive multi-peril insurance policy generally will cover all risks that are not specifically excluded, meaning that meteorite damage would generally be covered. The dwelling portion of the homeowner policy is very broad and if damage from falling objects is not listed in the exclusions, it is generally covered. Russian authorities estimate the meteor that exploded in the sky over the Ural Mountains region caused more than $US30 million ($A29.12 million) in damage. "Around 100,000 homeowners were affected (by Friday's incident). The damage is estimated at more than 1 billion rubles ($US30 million)," the governor of the central Russian region of Chelyabinsk, Mikhail Yurevich, said at a press conference. The latest update is regional officials believe the damage from the explosion could cost as much as $33 million dollars to repair, while others expect this figure to rise. The Tunguska Meteor of 30 June 1908 Before the Chebarkul Meteor of 15 February 2012, the only large meteoroid impact for which modern accounts existed was the June 30, 1908 Tunguska event. The following account of the event is taken from ScienceDaily, July 1, 2008, which was adapted from materials provided by Science@NASA; the original article was written by Dr. Tony Phillips. The Tunguska event razed the Siberian forest over an area of 800 square miles. The year is 1908, and it's just after seven in the morning. A man is sitting on the front porch of a trading post at Vanavara in Siberia. Little does he know, in a few moments, he will be hurled from his chair and the heat will be so intense he will feel as though his shirt is on fire. That's how the Tunguska event felt 40 miles from ground zero. June 30, 2008, is the 100th anniversary of that ferocious impact near the Podkamennaya Tunguska River in remote Siberia--and after 100 years, scientists are still talking about it. "If you want to start a conversation with anyone in the asteroid business all you have to say is Tunguska," says Don Yeomans, manager of the Near-Earth Object Office at NASA's Jet Propulsion Laboratory. "It is the only entry of a large meteoroid we have in the modern era with first-hand accounts." While the impact occurred in '08, the first scientific expedition to the area would have to wait for 19 years. In 1921, Leonid Kulik, the chief curator for the meteorite collection of the St. Petersburg museum led an expedition to Tunguska. But the harsh conditions of the Siberian outback thwarted his team's attempt to reach the area of the blast. In 1927, a new expedition, again lead by Kulik, reached its goal. "At first, the locals were reluctant to tell Kulik about the event," said Yeomans. "They believed the blast was a visitation by the god Ogdy, who had cursed the area by smashing Risk Frontiers Briefing Note 249 page 5

6 trees and killing animals." While testimonials may have at first been difficult to obtain, there was plenty of evidence lying around. Eight hundred square miles of remote forest had been ripped asunder. Eighty million trees were on their sides, lying in a radial pattern. "Those trees acted as markers, pointing directly away from the blast's epicenter," said Yeomans. "Later, when the team arrived at ground zero, they found the trees there standing upright but their limbs and bark had been stripped away. They looked like a forest of telephone poles." Such debranching requires fast moving shock waves that break off a tree's branches before the branches can transfer the impact momentum to the tree's stem. Thirty seven years after the Tunguska blast, branchless trees would be found at the site of another massive explosion Hiroshima, Japan. Kulik's expeditions (he traveled to Tunguska on three separate occasions) did finally get some of the locals to talk. One was the man based at the Vanara trading post who witnessed the heat blast as he was launched from his chair. His account: Suddenly in the north sky the sky was split in two, and high above the forest the whole northern part of the sky appeared covered with fire At that moment there was a bang in the sky and a mighty crash The crash was followed by a noise like stones falling from the sky, or of guns firing. The earth trembled. The massive explosion packed a wallop. The resulting seismic shockwave registered with sensitive barometers as far away as England. Dense clouds formed over the region at high altitudes which reflected sunlight from beyond the horizon. Night skies glowed, and reports came in that people who lived as far away as Asia could read newspapers outdoors as late as midnight. Locally, hundreds of reindeer, the livelihood of local herders, were killed, but there was no direct evidence that any person perished in the blast. "A century later some still debate the cause and come up with different scenarios that could have caused the explosion," said Yeomans. "But the generally agreed upon theory is that on the morning of June 30, 1908, a large space rock, about 120 feet across, entered the atmosphere of Siberia and then detonated in the sky." It is estimated the asteroid entered Earth's atmosphere traveling at a speed of about 33,500 miles per hour. During its quick plunge, the 220-million-pound space rock heated the air surrounding it to 44,500 degrees Fahrenheit. At 7:17 a.m. (local Siberia time), at a height of about 28,000 feet, the combination of pressure and heat caused the asteroid to fragment and annihilate itself, producing a fireball and releasing energy equivalent to about 185 Hiroshima bombs. "That is why there is no impact crater," said Yeomans. "The great majority of the asteroid is consumed in the explosion." Yeomans and his colleagues at JPL's Near-Earth Object Office are tasked with plotting the orbits of present-day comets and asteroids that cross Earth's path, and could be potentially hazardous to our planet. Yeomans estimates that, on average, a Tunguska-sized asteroid will enter Earth's atmosphere once every 300 years. Risk Frontiers Briefing Note 249 page 6

7 Time for future meteor impact defence plans? The Russian meteor explosion appears to be one of the most stunning cosmic events above Russia since the 1908 Tunguska Event in which a massive blast most scientists blame on an asteroid or a comet ripped through Siberia. This event alongside the 2012 DA14 asteroid passing by earth has sent off alarm bells ringing in some Russian circles about this being the time for joint global action on the space safety front. ``Instead of fighting on Earth, people should be creating a joint system of asteroid defence,'' the Russian parliament's foreign affairs committee chief Alexei Pushkov wrote on his Twitter account late Friday. "Instead of creating a (military) European space defence system, the United States should join us and China in creating the AADS - the Anti- Asteroid Defence System,'' the close ally of President Vladimir Putin wrote. The last meteorite strike was recorded in Sudan in Astronomers spotted a meteor heading toward Earth about 20 hours before it entered the atmosphere. It exploded over the vast African nation, but caused no known injuries. Hundreds of smaller meteorites strike the Earth s surface every year, although only 10 to 20 are detected. Such meteorites usually reach the surface having been burned down by the atmosphere and are too small to cause damage. Risk Frontiers Briefing Note 249 page 7

8 Global meteor impact locations: Figure 4 - Every meteorite fall on earth mapped or at least those we know about. These impact zones show where scientists have found meteorites, or the impact craters of meteorites, some dating back as far as the year 2,300BC. The data is from the US Meteorological Society and doesn't show those places where meteorites may have fallen but not been discovered (Guardian News and Media Limited 2013). Risk Frontiers Briefing Note 249 page 8

9 Figure 5 - Close up of impacts zones found in Australia. Interesting cluster in Southern Australia (Guardian News and Media Limited 2013). Risk Frontiers Briefing Note 249 page 9

July 2008 Page 1. Our closest call, 100 Years Ago... Story from 30jun_tunguska.htm?176186

July 2008 Page 1. Our closest call, 100 Years Ago... Story from 30jun_tunguska.htm?176186 Our closest call, 100 Years Ago... Story from http://science.nasa.gov/headlines/y2008/ 30jun_tunguska.htm?176186 The year is 1908, and it s just after seven in the morning. A man is sitting on the front