A giant fireball exploded in Earth's atmosphere in December, according to NASA.
It is the second largest explosion of its kind for 30 years, and the largest since its emergence in Chelyabinsk, Russia, six years ago.
However, the incident went unnoticed until now when it happened over the Bering Sea, on the Russian peninsula of Kamchatka.
As it exploded, the bricks generated 10 times the energy released by the nuclear bomb in Hiroshima.
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Lindley Johnson, NASA's Planetary Defense Chief, told the BBC that such a large explosion only takes place two or three times every 100 years.
Around noon, local time on December 18, the asteroid crossed the atmosphere at a speed of 32 km / s, on a steep road of seven degrees.
The meteor, with a several meter extension, exploded 25.6 km from the Earth's surface, with a power of 173 kilotons.
"It is equivalent to 40% of the energy released in Chelyabinsk, but as it happened over the Bering Sea, it did not have the same kind of effect and it was not shown in the news," said Kelly Fast in the near-observation observation program. by NASA.
"It's another thing we have in our defense: our planet is full of water."
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Quickly talked about the incident below 50th Lunar and Planetary Science Conference which takes place in Woodlands, USA, between March 18 and 22.
"Problems without passports"
Military satellites discovered the explosion last year and the US Air Force passed this information to NASA.
Johnson explained that the fireball went through an area close to the routes that commercial aircraft fly between North America and Asia.
For this reason, researchers have been in contact with various airlines to find out if they saw the event or not.
In 2005, the Congress asked NASA to identify by 2020 it 90% of near-asteroids nearby of a size of 140 meters or more.
Space bars of this size have been called "pass-free problems" because they are expected to affect the entire regions if they collide with the ground.
But researchers consider it This task will take at least 30 years.
Once a nearby object is identified, NASA has successfully calculated where the effect will occur, based on accurate circuit data.
For example, in June 2018, the small 3 meter asteroid 2018 LA It was discovered by an observatory in Arizona, the United States, eight hours before it made an impact.
The Observation Center near NASA's Jet Propulsion Laboratory (JPL) accurately determines its circuitry and these data were used to calculate the probable impact zone.
The information showed that the rock would probably have influence in southern Africa.
As shown in the calculations, The fireball was captured by the security cameras on a farm over the Botswana sky.
Later fragments of the space object were found in the area.
However, the latest explosion shows that large objects can collide with the ground without warning, emphasizing the need to improve monitoring techniques.
A more robust monitoring network depends not only on telescopes on Earth, but also on observatories in space.
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A project under development launches a called telescope NeoCam to a point in space from which it can distinguish and characterize potentially dangerous asteroids greater than 140 meters.
"The idea is to get as close as possible to the goal of Congress proposing NASA to find 90% of the almost earthly asteroids of 140 meters or more," said Amy Mainzer, lead researcher at JPL's NeoCam project.
If the observatory does not start in space, projections show that it will take many decades to reach this goal with the existing tools from the field, he added.
Although the researcher adds, it could be accelerated with an infrared telescope.
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