But others note that Jupiter's powerful gravitational field can just as easily send an object into Earth's path as push it deeper into space.

VOA: special.2009.08.25

Many scientists believe that a huge object from space hit Earth about 65 million years ago.

VOA: special.2009.01.20

Science fiction writer Arthur C.Clarke described an object left on the moon to let aliens know when humans were able to travel in space.

VOA: standard.2010.04.16