Richard Dawkins espouses this view in his interview with Ben Stein in the documentary Expelled: No Intelligence Allowed. Moreover, Nobel Laureates Francis Crick and Leslie Orgel (somewhat playfully) held that life must have been planted here from outer space.
But of course, this hypothesis only pushes life’s origin back a step. While this hypothesis would explain the origin of life on Earth, it still wouldn’t explain the origin of life. Therefore, this earlier improbability would still warrant an explanation.
Moreover, consider what an admission this is! These naturalistic scientists are claiming that an intelligent designer brought life to Earth. However, they are specifying that it must be a natural designer. Of course, this is special pleading at its worst. Intelligent Design theorist Philip Johnson comments, “When a scientist of Crick’s caliber feels he has to invoke undetectable spacemen, it is time to consider whether the field of prebiological evolution has come to a dead end.”
 Stein, Ben. Expelled: No Intelligence Allowed. Premise Studio/ USA: n.p., 2008.
 Crick, Francis. Life Itself: Its Origin and Nature. New York: Simon and Schuster, 1981; Crick, Francis and Leslie Orgel. “Directed Panspermia” Icarus 19, 1973. 341-346.
 Johnson, Phillip E. Darwin on Trial. 2nd ed. Downers Grove, IL: InterVarsity, 1993. 111.