NASA wants to know when a space object is threateningly approaching our planet, so that it can get ready for a possibly disastrous effect. For this, it launched the Planetary Defense Coordination Office (PDCO), which should detect any approaching asteroid or comet as early as possible. However, this doesn’t always happen, and a recent event is the best example for it. Although it was carefully tracked, an asteroid was detected only three days before it reached the closest point to our planet.
The asteroid was spotted when it had already got extremely close to Earth
The asteroid in question was called 2017 YZ4, which came close to Earth this week, on Thursday morning. It travelled only 138,500 miles away from our planet, which is about 58 percent of the distance between Earth and the moon. Although it was getting extremely close, PCDO managed to spot it approaching only on Christmas day.
This is a bit unusual, since NASA kept a close eye on the 2017 YZ4 asteroid since it was first discovered. However, they couldn’t tell if it posed a real collision danger. As it was spotted approaching Earth, NASA could take some measurements and discovered it was actually smaller than PCDO’s objects of study. It only measured 15 meters across, while the asteroids of interest for PCDO had to be at least 30 meters across.
NASA pays more attention to bigger asteroid which are usually more dangerous
NASA chooses to concentrate on bigger objects since they are more likely to survive a journey through Earth’s atmosphere and cause significant damage. For instance, the popular meteor which exploded above Chelyabinsk, Russia in 2013 only measured 20 meters across. In fact, it didn’t even make it to the ground in one piece, otherwise the damage would have been a lot bigger. Also, the speed of the asteroid can influence how destructive it gets.
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