A giant fireball zoomed through the Earth's atmosphere and fell into the southern Atlantic Ocean on Feb. 6. The fireball likely exploded approximately 30 kilometers above the ocean yet, surprisingly, almost no one noticed it.
The fireball is said to be the largest one to hit the Earth since the Chelyabinsk explosion in February 2013. Yes, it is that significant.
The Unnoticed Giant
The incident happened around 9 a.m. EST (14:00 UTC) off the coast of Brazil. The fireball was brimming with energy that is said to be equivalent to 13,000 tons of TNT. If compared, the Chelyabinsk explosion boasted groundbreaking energy of 500,000 tons of TNT as it passed through the skies above the Ural Mountains.
Based on the high-altitude impact felt, the space rock is estimated to be about 5-7 meters (16-23 feet) in width. In comparison, the rock that caused the Chelyabinsk explosion was almost 20 meters (65 feet) in width. Looking at the numbers, the Feb. 6 event seems like a repeat of the Chelyabinsk, so the question is, why didn't it create noise right after it happened?
Why Unnoticed?
With the seemingly significant descriptions, the question is why the incident went unnoticed.
Astronomer Phil Plait investigated and made some calculations to explain what happened.
A big chunk of rock from space has the ability to cause a blazing and shattering impact as it enters the Earth's atmosphere. If the rock is big, it can go deep into the atmosphere first before burning. The rock then compresses the gas in front of it, increasing the temperature of the meteoroid until it is eventually glowing. Next, it can either evaporate or blow off, which leads to the rock slowing down or completely disappearing.
If the rock is bigger, then it can shatter as the atmosphere puts massive pressure on it. The resulting debris burn up, turning it into smaller pieces. The Chelyabinsk meteor broke up as it entered Earth's atmosphere and was observed as a series of bright lights, which can occur quickly as tremendous energy is burned away at the same time. This unravelling is why the event was so significant that it was called an explosion.
But of course, a major event cannot create a buzz if there is no audience.
While the Feb. 6 event would have been an epic one, it occurred some 1,000 kilometers, about 620 miles, away from the coast of South America, east-southeast of Rio de Janeiro.
"That's far enough out over the ocean that it's unlikely anyone saw it," says Plait.
Chelyabinsk happened in a rather more populated location, with more than 1 million residents.
NASA came to know about the giant fireball through the military, which is always on the lookout for explosions in the air for safety reasons. However, the amount of information that NASA's Jet Propulsion Laboratory received was limited to the basics such as time and direction.
Implications
Despite the growing buzz, it is safe to say that impacts like these aren't unusual. In fact, events like these occur numerous times in a year, but because about 71 percent of the Earth's surface is covered by water, most of these space rocks crash into oceans.
Although such incidents are relatively common, this still calls for better ways to detect such events. While the rocks can get very small while passing through the atmosphere and often land in an ocean, causing relatively little damage, it is still good to know when one is coming.
