Published: Sep 23, 2011 3:33 PM EDT

CAPE CANAVERAL, Fla. (AP) - A 6-ton NASA satellite is plummeting back to Earth.
    
The old spacecraft is expected to hit sometime Friday afternoon or early evening Eastern time. It won't be passing over North American during that period, but scientists aren't sure exactly where it will strike. But since nearly three-quarters of the world is covered in water, it is likely to be a splashdown.
    
The NASA climate satellite is about the size of a bus. It's expected to break into more than 100 pieces, and most of it will burn up as it plunges through the atmosphere. About 25 large metal chunks are expected to survive and scatter somewhere on the planet.
    
The satellite was launched twenty years ago aboard space shuttle Discovery.

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