(Illustration courtesy of NASA)

Is there anyone out there? The answer is almost certainly yes, a top NASA scientist said this week.

The search for alien life has long since shifted from a question of whether it exists to a question of when we'll find it.

And NASA's chief scientist Ellen Stofan predicted this week that the answer could come within the next decade.

"I believe we are going to have strong indications of life beyond Earth in the next decade and definitive evidence in the next 10 to 20 years," Stofan said at a panel on Tuesday, according to the Los Angeles Times. 

The search has taken a number of forms, but one of the most important facets has been the task of searching the universe for signs of liquid water, which contains some of the essential building blocks of life as we know it.

[Do we really want to know if we’re not alone in the universe?]

So far, scientists have found plenty of evidence that water is, simply put, everywhere.

There is evidence to suggest that vast oceans could well be sloshing around under the surface of moons and dwarf planets within our own solar system. Mars might have once had an expanse of liquid water on its surface. And in our galaxy, the Milky Way, billions of stars are capable of having orbiting planets that hold the building blocks of life, a recent study found.

And in a new study published Wednesday in Nature, researchers announced the first-ever spotting of complex organic molecules -- the ones necessary for building amino acids and proteins -- in the planet-forming region of a young star system. This could mean that these building blocks are actually pretty common, and that many star systems have the capacity to seed life on their planets.

Within our own solar system, Europa, an icy moon belonging to Jupiter, is probably the greatest object of speculation.

Beneath the freezing cold surface could well be a massive, liquid collection of water, scientists believe. That environment might not be so different from the deep frozen lakes of our own polar regions, which we now know to contain intrepid microbes.

[Remastered image shows the icy surface of Jupiter’s moon in living color]

Europa is promising enough that NASA has proposed a mission to check the moon out from a better vantage point.

This icy moon has also taught us that liquid water -- and perhaps the early building blocks of life -- doesn't require the "prefect" proximity to a nearby sun, which scientists used to believe was necessary to heat up a planet or moon just enough so that water could remain in liquid form. They believe that Europa's water, for example, is heated up just enough by the gravitational force of its planet Jupiter to remain liquid beneath the surface despite being far from our sun.

Now, scientists believe that our search for life can extend to moons orbiting planets, not just planets orbiting suns, which opens up endless possibilities.

"We now recognize that habitable zones are not just around stars, they can be around giant planets, too," Jim Green, director of planetary science at NASA, said according to the LA Times. "We are finding out the solar system is really a soggy place."

[Two new exoplanets are more Earth-like than any we’ve found before]

And there are other possible places where we might see this kind of phenomenon, which NASA has helpfully outlined here.

"NASA science activities have provided a wave of amazing findings related to water in recent years that inspire us to continue investigating our origins and the fascinating possibilities for other worlds, and life, in the universe," Stofan said, according to NASA. "In our lifetime, we may very well finally answer whether we are alone in the solar system and beyond."

Don't worry. She isn't really talking about the kind of alien life that might have haunted your nightmares or been featured in countless science-fiction movies.

"We are not talking about little green men," Stofan said. "We are talking about little microbes."

Want more science? Give these a click:

For the first time, scientists find complex organic molecules in an infant star system

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The water on our planet may be older than the sun, which is good news in the hunt for extraterrestrial life

Scientists hit new milestone in search for water on planets outside our solar system

 

A hot water clue to life on Saturn moon