Here's Why Astronomers Did Not Detect The Russia Meteor Ahead Of Time
It was an incredible day for near-Earth objects, with two rare cosmic events occurring on the same day.
First, a tiny asteroid actually hit Earth, creating a significant explosion over eastern Russia around 9:30 a.m. on Feb. 15 in that part of the world.
Less than 24 hours later, a larger asteroid, 2012 DA14, passed safely above Earth at a distance of around 17,200 miles, the closest an object of that size has come to our planet since scientists began monitoring the skies. Astronomers had been tracking that asteroid for about a year and knew that it posed no danger of colliding with Earth.
NASA held a teleconference this afternoon to discuss both events.
Here's what they know so far:
The Russia meteor is estimated to have been about 50 feet in diameter, which is considered a tiny asteroid, according to meteor expert Bill Cooke.
Scientists say they did not detect the asteroid because it came out of the daytime sky. These are nearly impossible to find ahead of time because telescopes can only spot asteroids during the night.
The small asteroid hit the atmosphere moving at a blistering 40,000 miles per hour. That's more than twice as fast as asteroid 2012 DA12 is moving. The space rock lasted about 30 seconds in the atmosphere before breaking apart 12 to 15 miles above Earth's surface.
When the asteroid broke apart it produced an explosion that created a shockwave, which struck the Russian city of Chelyabinsk below.
In order for a tiny asteroid to slow down, the atmosphere will absorb that energy and emit it as heat and light.
"The event must have been brighter than the sun if you were there to watch it," said Paul Chodas, research scientist in NASA's Near Earth Object Program Office.
The shockwave caused windows to break and walls to collapse, injuring hundreds of people as a result. No injuries were caused by fragments falling from the sky. There are undoubtedly pieces of rock on the ground, but none have been verified with certainty yet.
The energy released by the event was 500 kilotons, according to Cooke, leaving a trail in the sky about 300 miles long. This is the largest recorded meteorite impact since the Tunguska explosion in 1908.
Scientists also verified that the Russia meteor is not related to asteroid 2012 DA14 in any way. They know this because asteroid 2012 DA14 is about three times bigger, at 150 feet in diameter, and it was traveling in a different direction, from south to north.
Fortunately both asteroids were relatively small in nature. Tiny asteroids like the one that exploded over Russia hit the Earth on average about once every 100 years, Chodas said. Although it is an incredible coincidence that both phenomenons happened on the same day.
The bigger threat to Earth is large asteroids, like the one that ultimately wiped out the dinosaurs. NASA, the lead agency in worldwide asteroid tracking, says it has found about 95 percent of large near-Earth asteroids, asteroids that are close enough and big enough to pose a hazard to Earth, though not necessarily headed in our planet's direction.