Scientists are torn on whether extraterrestrial life is abundant, rare or nonexistent. With 300 billion stars in the Milky Way, the late astronomer and futurist Carl Sagan figured there could be up to 10,000 advanced civilizations in our galaxy alone. Others, however, think not only are habitable planets rarer than thought, the odds of life forming are slight even on a promising world. In other words, we might be completely alone in our galaxy or even the universe.
Despite pessimism among some researchers, NASA has often implied that if a planet has the same conditions as Earth, it will automatically have life. "I see that as a marketing thing by NASA to interest people in planetary searches," said astronomer Caleb Scharf, who co-authored a paper on the odds of life forming on a planet. "I think [the chances] could be a lot lower, personally."
That's reinforced by another stark reality. "We haven't seen life everywhere we've looked so far," said astrobiologist Lauri Barge. "If life really requires some unique conditions to emerge, obviously Earth had them, but how many other planets would have them?"
We another planet to mess up. The good news? That will not be allowed. To read more, click here.