A question regarding the topic bearing the forum's name. Namely, how massive does an object in outer space have to be to keep you from being like Dr. Smith, Will(Danger)Robinson & company-namely lost in space. Namely to put escape velocity beyond your jumping/running speed(in a spacesuit of course) I'm sure it depends some on the density as well as mass. Is there a known ballpark mass threshold that makes it impossible to jump up beyond the point of no return? Is Diemos big enough? Phobos?(the moons of Mars) I know that in the movie "Deep Impact" one of the astronauts on the Messiah was supposedly blasted to escape velocity by one of the gas jets of the 500 gigaton(1 quadrillion#) icy chunk that was the fictional Comet Wolf Beterman. That however, was from a jet of gas. Would an iceball that size have enough gravity to keep a spacesuited astronaut from "flying off into space by his own metabolic power?