Bus-Sized Asteroid Zips Past Earth 2011 MD comes within 7,500 miles By Rob Quinn, Newser Staff Posted Jun 28, 2011 2:42 AM CDT 3 comments Comments NASA's chart of 2011 MD's path. (NASA) (Newser) – Astronomers got a treat yesterday when an asteroid roughly the size of a bus passed within 7,500 miles of Earth—closer than many satellites. The space rock, named 2011 MD, was over the south Atlantic near Antarctica at the time of its closest approach, reports the Christian Science Monitor. The asteroid was only spotted a few days ago, but experts say it was too small to have survived entering Earth's atmosphere even if it was on a path to score a direct hit. The asteroid, which had been in an orbit around the sun so Earth-like that astronomers initially thought it was a piece of space junk, was sent off on a new trajectory through the solar system by its close brush with Earth. Asteroids the size of 2011 MD pass close by Earth every 6 years or so on average, although one came even closer to our planet just a few months ago.