An out-of-control US spy satellite could hit the Earth at the end of February or early March.
US government officials say the satellite has lost power and they are monitoring the situation.
But a spokesman said lots of satellites had come out of orbit and fallen back to Earth harmlessly over the years.
It's thought the satellite weighs about 9,072kg - the equivalent weight of two elephants -and is about the size of a small bus.
The satellite might contain hazardous materials as well as top secret spy information.