"I think in the next 20 years, we will find out we are not alone in the universe," said Kevin Hand, NASA's deputy chief scientist of the Solar System Exploration Directorate, at the 18th biennial conference of the Palaeontological Society of Southern Africa.
Two experts joined The Daily Circuit to discuss technological and scientific advances that would allow humans to make such a discovery.
How we could discover intelligent life on other planets
We need to detect more planets.
"We now have the ability to [find planets] by detecting little wobbles of parent stars, especially lower mass stars that wobble more easily when a giant planet is going around them," said Bob Berman, columnist for Astronomy. "We can calculate the period and if the period is regular we can know what the mass of the planet is, how many they are. And now there's a new method that actually sees the slight dimming of the star if the planetary orbit is aligned just right so that it passes in front of the star regularly."
If most, if not all, of the 400 billion stars in the galaxy have planets and we assume perhaps 1 in 1,000 planets have a friendly habitable disposition, that leaves millions of potential Earth-like planets, Berman said.
Those planets must have elements that sustain life.
The biggest green light for scientists is oxygen, Berman said.
"If we saw the signature of oxygen in the reflected spectrum of a planet, that'd be very intriguing," Berman said. "Generally you don't get free oxygen; oxygen loves to bind with stuff... Here on the Earth we have free oxygen for only one reason: plants release it. They take the oxygen that's bound up, mostly as CO2, and release it as oxygen."
A planet also must be a certain distance from its parent star in a habitable zone, said Jerome Orosz, professor of astronomy at San Diego State University.
Planets must have an equilibrium temperature that allows liquid water and that comes from its distance from the parent star. In our solar system, for example, Mercury is too close to the sun and too hot for liquid water. Mars is a bit too far from the sun and water on the planet would be frozen.
The life on other planets would need the intelligence to communicate and the interest to find other life forms.
"We can look on Earth here and we see that there are intelligent creatures like dolphins and whales that may be just as intelligent as we are and show no inclination to build machines and hurl themselves through space or even hurl themselves out of the ocean," Berman said. "It could be that our desire to communicate and create radio and TV and to fly across space... by itself may be an unusual thing."
Do you believe in the existence of extraterrestrial intelligent life? Why or why not? Leave your comments below.