NASA's recent capture of two large asteroids passing close to Earth was not just a routine observation. One of the asteroids had a small 'moonlet' in orbit.

While not close enough to worry about, the encounter gave astronomers an opportunity to get a closer look at the object. Doing so can help us learn more about such asteroids, as w

MK nor 2011 UL21, as the asteroids are named, came close enough to pose a hazard, but both were within range of radar imaging systems. So NASA got a few happy snaps to mark the occasion. These are more than just asteroid flyby souvenirs.

The scientists tracked the two asteroids at NASA's Jet Propulsion Laboratory in Southern California which made a flyby but did not pose a hazard