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While we were all busy getting ready for the holiday season in December, a piece of space rock was hurtling towards Earth, and on December 18 it hit our atmosphere, became a luminous fireball, and exploded with 10 times the energy of the Hiroshima atomic bomb – and we all totally missed it.
The blast was the biggest since the infamous Chelyabinsk meteor that exploded over the Russian oblast in 2013, injuring hundreds, and the second largest of its kind in 30 years. Yet, it was likely only witnessed by what we imagine were bemused sea lions and surprised whales, as it exploded over the Bering Sea.
US military satellites picked up on the explosion last year and subsequently referred it to NASA to investigate. We are hearing about it now, as Dr Kelly Fast, near-Earth objects observations program manager at NASA, was discussing it earlier today at the 50th Lunar and Planetary Science Conference in Houston, Texas, reports BBC News.
These are thought to be the first photos of the December 18 meteor.
So, what happened?
The meteor, which was several meters across, came whizzing through the atmosphere towards Earth at a speed of 32 kilometers (20 miles) per second at a steep trajectory of 7°. It appeared at 11.50pm UT (midday local time), 25.6 kilometers (16 miles) above the planet’s surface, before the friction of the atmosphere caused it to explode – which it did with an impact of 173 kilotons of TNT.
For comparison, the Little Boy atomic bomb dropped on Hiroshima on August 6, 1945, detonated with an energy release of 15 kilotons, and the Fat Man bomb dropped on Nagasaki three days later exploded with 20 kilotons.
According to Peter Brown, a meteor scientist and professor at the University of Western Ontario, Canada, who first clocked the meteor in measurements picked up by infrasound monitoring stations globally, the meteor was 10 meters (33 feet) across and had a mass of 1,400 tons.
These infrasound stations were initially set up during the Cold War to detect nuclear explosions by picking up low-frequency acoustic waves inaudible to humans. Finding the source and location of an explosion means combining the data from multiple stations, which could explain the delay in announcing the fireball.
What does this mean for Earth?
Not a lot, frankly. Earth is regularly pummeled by space rocks. Think how often we report on meteor showers (the Lyrids are up next in April, by the way). And 75 percent of Earth’s surface is water, so many burn up over the sea or disappear into it, and we are none the wiser (others, of course, like to make sure they are seen). Admittedly, Russia gets more than its fair share, but it’s the biggest country in the world so that’s not too surprising.
Lindley Johnson, planetary defense officer at NASA, told BBC News a meteor this size is only expected about two or three times every 100 years. This meteor was also only about 40 percent of Chelyabinsk's, which briefly outshone the Sun. Luckily we have plenty of people here on Earth monitoring asteroids for potential impact, such as NASA's Center for Near-Earth Object Studies, as well as how we could potentially deflect them.
So far there is no footage of this latest meteor. However, it came in not far from routes taken by commercial airplanes, so researchers are having airlines check for reported sightings. Not like the Chelyabinsk meteor, of which there is so much footage, researchers resorted to YouTube to study it.
Wait for itttttt. Chelyabinsk meteor, February 15, 2013.
