LOS ANGELES (AP) - The giant asteroid Vesta got clobbered not once but twice, and it has the scars to prove it.
    
When the Hubble Space Telescope first spied a huge depression in the asteroid's south pole, scientists believed it was carved by a collision with a celestial object, most likely a smaller asteroid.
    
But a recent closer inspection revealed a surprise -- two massive overlapping craters.
    
The double strikes occurred relatively recently - 1 to 2 billion years ago - and came to light only after researchers pored over high-resolution images snapped by the NASA Dawn spacecraft, which slipped into orbit around Vesta last year.
    
The finding is reported in Friday's issue of Science, which published a series of papers on the $466 million mission.