At 04:51 GMT today, asteroid 2017 BH30 is yet another newly discovered object that flew past the Earth at a close distance. Discovered by the Catalina Sky Survey only on Sunday, the space rock is thought to be around 4-10 meters in diameter passing at a very close distance of 40,563 miles. That’s 6 times closer than the distance to the Moon. This is the third asteroid this month after 2017 AG13 and 2017 BX that were also discovered only days before passing within the distance of the Moon and Earth.
Should we be alarmed?
Although smaller than the previous two encounters, this asteroid passed perilously closer to the Earth. It passed almost as close as geosynchronous satellites. Although this sounds alarming, asteroids of this size do enter the Earth’s atmosphere from time-to-time and often don’t make it all the way to the ground once the harsh forces of re-entry have finished with them. By comparison, the Chelyabinsk meteor in Russia was thought to be 20 meters in diameter. The airburst caused some damage to structures and minor injury but still did not impact the ground nor were there any reported fatalities.
According to NASA’s Jet Propulsion Laboratory, asteroids the size of a car enter the Earth’s atmosphere roughly once a year by burning up and causing an impressive fireball but never reaching the ground. Asteroids the size of a football field (with the potential to cause significant localised damage) impact roughly once every 2000 years. The last significant impactor of this size was the Tunguska Event. It was not strictly an impact as evidence suggests it may have exploded before impact causing a devastating air burst over the Eastern Siberian Taiga on 30 June 1908. Estimates of its size are not exact but studies suggest it was between 60 to 190 metres in diameter.