To arrive at an answer, the space agency has announced it is questioning everything it knows about life forms so far.
For this, experts in astronomy, biology and geology have re-evaluated the markers indicative of alien life, it said.
And NASA published its new concept in a series of papers published in the scientific journal Astrobiology, reports Express.co.uk.
Until now, scientists have been scanning stars for signs of oxygen – a key element that supports life on earth.
But in a radical new step, scientists are now asking a pertinent question – what if alien lifeforms thrive in low-oxygen atmospheres. Or, if plant-life on a distant planet is not green but purple?