For a few hours on January 13, 2004, some astronomers believed that a 30-metre asteroid could strike the Earth in less than two days. The asteroid, named 2004 AS1, ended up passing 12 million kilometres away, but it demonstrates the difficulty asteroid hunters have searching for objects that could hit our planet. Had it struck, 2004 AS1 could have caused destruction on a city-wide scale. NASA currently has a program to search for asteroids larger than 1 km, and should locate them all by 2008. Other proposals have been suggested to search for smaller - and still dangerous - asteroids that threaten the Earth, but nothing has been approved yet.