We're going to detect alien life in the next decade, but not where you might think

Tiny, microbial life could be swarming deep below the surface of Mars or swimming in the underground oceans on Saturn's moon Enceladus, but that's not where we're likely to find the first life forms beyond earth.

The bad news is that the first alien life forms humankind will likely discover will be too far away to ever visit. But the great news is that we could detect these exotic beings extremely soon:

"I think we're probably going to be able to detect life on another planet in the next decade or so," Christopher Impey, who is an astronomer at the University of Arizona and author of over a dozen popular science books, told Business Insider. The way we're going to do it is "by exploring exoplanets that we're discovering in large numbers."

Exoplanets are planets that exist outside of our solar system. The closest exoplanet we know of so far is actually orbiting one of the nearest stars Alpha Centauri B about 4.3 light years from earth, but it would take current spacecraft technology well over 100,000 years to reach it.

Why exoplanets?

Discovering another life force beyond earth is going to be difficult no matter where astronomers look, but exoplanets have several advantages.

First, there are more earth-like exoplanets in our galaxy than in our solar system. Indeed, earth is the only real earth-like planet nearby, with Mars as a close but pretty disappointing second. As of right now, there are over 45 exoplanets in our galaxy thought to be potentially habitable.

I think we're probably going to be able to detect life on another planet in the next decade

Another advantage is that scientists can search for life on exoplanets inexpensively and efficiently with instruments on earth.

In contrast, large government agencies like NASA and the European Space Agency will likely have to land a robotic probe on the surface of Europa, or some of the other promising places in our solar system, to discover evidence of life. (The one exception could be Saturn's water-rich moon Enceladus.)

"They're billion-dollar, decade-long missions and NASA's budget is so tight that you can only do one big thing at a time," Impey told Business Insider about missions to land a probe on a nearby planet or moon.

On the other hand, with powerful telescopes on earth, scientists can sniff out alien life across the galaxy by inspecting the different cocktail of gases in these planets' atmospheres. Only planets with certain key elements and molecules will have the potential to spawn and sustain life.

The chemical recipe for life

However, scientists are still debating what that perfect cocktail is.

For example, until last year, the detection of oxygen - an crucial element for life on earth - within an exoplanet's atmosphere would have been an extremely exciting discovery and widely considered a sure sign for life.

But in May, 2014 a pair of researchers - Robin Wordsworth and Raymond Pierrehumbert - suggested that worlds with large amounts of liquid water could still have lots of oxygen but be completely devoid of life. That's because light from the planet's star could have enough energy to separate the hydrogen and oxygen atoms making up water vapor in the atmosphere, where the hydrogen could then escape to space, leaving behind the oxygen.

"Any claims about the remote detection of life beyond the solar system would be open to a lot of close scrutiny," Jack O'Malley-James told New Scientist for an article about the study. "So knowing more about the non-biological sources of atmospheric gases, coupled with methods for ruling those sources out, would help to make those claims more robust."

A new fleet of gigantic, revolutionary telescopes

While scientists like Wordsworth and Pierrehumbert are investigating what to look for, astronomers and engineers are working on the tools we'll use in the search for life outside our solar system by building the largest, most powerful telescopes in history.

"[Exoplanets] are far away and they're very faint," Impey told Business Insider. "You need a huge collecting area to get the light from a distance of an earth-like planet."

The collecting area of a telescope refers to the size of the part of the instrument, called the mirror, which collects the light from distant objects. Astronomers will then study this light to detect different chemical signatures in the atmosphere. Similar to how each human has a unique thumbprint, each element has a specific light signature, which astronomers can detect through a method called spectroscopy.

But, it's going to take the most powerful telescopes in history to detect the faint light signatures of these molecules on distant exoplanets. Right now, astronomers at institutes across the globe are building three gigantic, next-generation telescopes, two in Chile and one in Hawaii:

• The Giant Magellan Telescope (GMT) will be three times large than any current telescope and will produce images 10 times sharper than the Hubble Space Telescope. It's currently under construction at Las Campanas Observatory in La Serena, Chile and is scheduled to begin operations by 2024.
• The Thirty Meter Telescope (TMT) is expected to provide images that are 12 times sharper than the Hubble Space Telescope and was scheduled to begin operations atop Hawaii's dormant volcano Mauna Kea as soon as 2025. However, recent protests have temporarily halted construction.
• The European Extremely Large Telescope (E-ELT) will dwarf both the GMT and TMT with a mirror the size of half a soccer field! (See the image above.) Construction on the E-ELT began in June 2014 in Cerro Armazones, Chile, and this colossal telescope is scheduled to start operations in 2024.

These three huge telescopes each have the capability to observe distant worlds and maybe, just maybe, make the most important discovery in the history of the human race by answering that tantalizing question: Are we alone?