Posts Tagged ‘near earth asteroids’

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“Everybody talks about the Tunguska Event…” (De)Extinction Files: Cosmic Catastrophism

Fireballs caused by disintregrating asteroids streak through Earth’s skies at least twice per month on average, scientists say.

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A new map created by NASA researchers documents 556 fireball events — produced when small asteroids explode in Earth’s atmosphere — that occurred around the world between 1994 and 2013.

Fireballs, also known as bolides, are defined as meteors that blaze at least as brightly as the planet Venus in the sky.

Scientists compiled the new map using data collected by U.S. government sensors. That database is more complete than others previously available to NEO researchers, but it does not include every single fireball that blazed up over the last two decades, NASA officials said in the statement. So the actual number is higher than the 556 depicted on the map.

The map also charts the energy released by each fireball. The most powerful of all was the Russian meteor explosion, which occurred in February 2013 when a 65-foot-wide (20 meters) space rock detonated over the city of Chelyabinsk, injuring more than 1,200 people.

Scientists think there are about 1,000 potential “civilization-enders” at least 0.6 miles (1 kilometer) wide out there. NASA’s NEO Observations Program has already spotted about 96 percent of these mountain-size space rocks, and none of them pose a threat for the foreseeable future.

But there may be about 25,000 near-Earth asteroids at least 460 feet (140 m) in diameter, which could cause massive destruction on a local scale if they hit the planet. And many of them are cruising undiscovered through space.

Indeed, scientists have found just over 11,600 near-Earth asteroids of all sizes to date; the entire population likely numbers in the millions.

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This NASA graphic shows the orbits of all the known Potentially Hazardous Asteroids (PHAs), numbering over 1,400 as of early 2013.

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This diagram illustrates the differences between orbits of a typical near-Earth asteroid (blue) and a potentially hazardous asteroid, or PHA (orange). PHAs have the closest orbits to Earth’s orbit, coming within 5 million miles (about 8 million kilometers), and they are large enough to survive passage through Earth’s atmosphere and cause significant damage.

Currently there is no comprehensive dynamic map of our inner solar system showing the positions and trajectories of these asteroids that might threaten Earth.  The citizens of Earth are essentially flying around the Solar System with eyes closed. Asteroids have struck Earth before, and they will again – unless we do something about it. The probability of a 100 Megaton impact somewhere on Earth each and every year is the same as the probability of an individual being killed in an automobile accident each year – about .01%.  These odds are small, yet few among us would drive around each day without wearing a seat belt.  What precautions are we taking with our planet?

Between 2000 and 2013, a network of sensors that monitors Earth around the clock listening for the infrasound signature of nuclear detonations detected 26 explosions on Earth ranging in energy from 1-600 kilotons – all caused not by nuclear explosions, but rather by asteroid impacts.

These findings were recently released from the Nuclear Test Ban Treaty Organization, which operates the network.

To put this data in perspective, the atomic bomb that destroyed Hiroshima in 1945 exploded with an energy impact of 15 kilotons. While most of these asteroids exploded too high in the atmosphere to do serious damage on the ground, the evidence is important in estimating the frequency of a potential “city-killer-size” asteroid.

A list of the impacts shown in the video can be found here.

Join us as we investigate the hundreds of meteorites that have crashed to earth throughout history and the team of dedicated scientists working feverishly to protect us in the future. See how these men and women, using high-tech equipment, plan to fend off Apophis, a 250-ton behemoth heading directly for us.

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