As science continues to search the cosmos for evidence of intelligent extraterrestrials and, at the very least, for habitable planets that might harbor even non-intelligent life, one scientist is raising another eye-opening question: Was there a time in the far distant past when an advanced civilization actually lived on one of the planets of our solar system, long before earthlings evolved?

Pennsylvania State University astrophysicist Jason T. Wright suggests that ancient aliens may have lived on nearby planets hundreds of millions of years ago, before vanishing without a trace.

HuffPost asked Wright how far back in time he thinks aliens might have lived in our solar system and if some of them may still be lingering out there.

“It seems pretty clear there aren’t any now. That’s become more clear as we’ve explored the solar system robotically. In terms of large, intelligent, technological civilizations, that seems pretty case closed,” he said in an interview Friday.

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