The closest an asteroid has ever been observed to pass by the Earth is around 6,500 km (4,000 miles), by the asteroid 2004 FU162 on 31 March 2004. The asteroid, which measures only around 6 m (19 ft) across is too small to be classified as an asteroid (which must be at least 50m across) and would most likely have burned up in Earth’s atmosphere had it collided with the planet.