Asteroid danger: NASA scientist explains 'current HAZARD' and 'LARGE ONES' threat

Asteroid danger: NASA scientist explains 'current HAZARD' and 'LARGE ONES' threat

Asteroid impacts are a relatively frequent occurrence, with house-sized space rocks striking the Earth once every few decades or so. The last time

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Asteroid impacts are a relatively frequent occurrence, with house-sized space rocks striking the Earth once every few decades or so. The last time an asteroid this big hit the Earth was in February 2013, when a 65.6ft-wide (20m) meteor exploded over Russia’s Chelyabinsk Oblast without warning. The asteroid impact blew out windows in a wide radius, damaging more than 7,000 buildings and injuring more than 1,000 people with shards of razor-sharp glass. And the Earth is pelted much more frequently by smaller space rocks and sand-sized grains of cosmic dust.

According to Joanna Wendel at NASA’s Jet Propulsion Laboratory (JPL), roughly 100 tonnes of cosmic material “rain down” on Earth every single day.

Much of this material, and in particular pebble-sized rocks, shoots through the skies in the form of bright, streaking meteors or fireballs.

Ms Wendel wrote for NASA: “Occasionally, Earth passes through denser streams of small debris released from comets – that’s how we get meteor showers.

“Sometimes larger, chair-sized or even car-sized space objects enter Earth’s atmosphere and create really bright meteors, called fireballs or bolides, which disintegrate as they explode in the atmosphere.

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“Very rarely, every few decades or so, even larger objects enter the atmosphere, such as the house-sized object that streaked across the sky over Chelyabinsk, Russia, in 2013, producing a super-bright fireball and a shock wave that blasted out windows and broke down doors.”

With the frequency of asteroid impacts, it might seem as if scientists have been aware of this danger for many years, but Ms Wendel said asteroids are very much a “current hazard’.

Up until recently, astronomers believed the craters on the Moon were the result of ancient volcano activity and not asteroid impacts.

And it was only in the 1980s that scientists discovered it was an asteroid impact that wiped out the dinosaurs 65 million years ago.

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The asteroid expert said: “After scientists found the Chicxulub Crater in the Gulf of Mexico, this idea became more certain.

“In 1994, the world witnessed similar-sized impacts happening on in near-real-time when fragments of comet Shoemaker-Levy 9 impacted Jupiter – that’s when we really started to understand that large asteroid impacts could still happen today.”

But what about these bigger asteroids striking the Earth? What is the danger of truly killer-sized objects barreling towards our home planet?

By 2010, NASA’s asteroid trackers have mapped out around 90 percent of the estimated 1,000 Near-Earth asteroids (NEA) measuring 3,280ft (one kilometre) across or more.

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These fearsome asteroids were at the top of NASA’s priority list due to their potential to cause widespread chaos across the planet.

Luckily none of these space rocks appear to pose any threat to the safety of the Earth.

Ms Wendel said: “NASA’s search programs are still finding a few of these large asteroids every year and astronomers think that there are still a few dozen yet to be found.

“Because of NASA’s efforts, 90 percent of the risk of sudden, unexpected impact of an unknown large asteroid has been eliminated.”



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