Asteroid 2014 JO25, an asteroid the size of the Rock of Gibraltar, has just passed by Earth at a distance of only 1.8 million km (1.1 million miles) – the closest big asteroid since 2004. The next known similar event will occur in 2027 when the half-mile-wide asteroid 1999 AN10 will fly by at about 380,000 km (236,000 miles).