While attending an event for the series One Strange Rock in Los Angeles, they answered the burning question: Are we alone in the universe?
The discussion was based around filmmaker Darren Aronofsky’s latest series that explores the wonders of Earth.
Canadian astronaut Chris Hadfield, who has spent 4,000 hours in space, said: “We’ve basically proven that every star has planets.
“Then you start doing the math.”
“We have to think through things to find the evidence”
Within the constraints of the observable universe, there could be 1,000,000,000,000,000,000,000,000 (or septillion) stars, according to astronomer David Kornreich.
And he conceded to Space.com that the number could be a gross underestimate.
If every one of those stars has at least one planet, then he said, it seems conceivable that life would exist elsewhere.
Former astronaut Jeff Hoffman also believes there is life in the universe.
He said: “But as a scientist, I look for evidence.
“And as yet, we have no evidence. So I have nothing to support my belief. But I still believe it.”
But Mae Jemison, the first African-American woman in space said: “We have to think through things to find the evidence.
Other astronauts also believe Earth could be totally unique.
There could be something special about our solar system, the Milky Way, and planets that makes life possible here and nowhere else, however unlikely that may be.
But the astronauts added that proof of life could actually be very close to home.
Hadfield said: “If we can find one fossil on Mars, or one little tube worm deep under the oceans of Europa or Enceladus, then the universe is full of life.”
But that may not necessarily mean spaceships and ray guns.
The norm, said Hadfield, could be that “life is relatively common”, but “complex, intelligent life is rare”.
The new TV series, One Strange Rock, debuts Monday on National Geographic.