An asteroid nine-times the size of an ocean liner that flew past us on a "near-Earth" trajectory last month is an entirely new type of space rock, scientists have discovered.
Arecibo's Ellen Howell said: "Asteroid QE2 is dark, red, and primitive — that is, it hasn’t been heated or melted as much as other asteroids.
"QE2 is nothing like any asteroid we've visited with a spacecraft, or plan to, or that we have meteorites from. It's an entirely new beast in the menagerie of asteroids near Earth," reports Space.com.
QE2 was an excellent opportunity to study an asteroid, particularly one that has its own moon which is about 600 metres wide.
According to Nasa 16% of asteroids larger than 200 metres have their own satellites, but it's still pretty unique to see one so close to Earth.
By examining the orbit of the moon scientists should be able to determine the asteroid's gravitational pull and from that, its composition.
The asteroid was discovered in 1998 by the prestigious Massachusetts Institute of Technology and, despite the comparisons, was not named for the QE2 cruise ship. Its size has instead been more accurately compared to San Francisco's Golden Gate Bridge.
The space rock completes one lap around the sun every 3.8 years.