Planets outside our solar system that orbit stars are known as exoplanets. Since 1992, scientists have discovered more than 3,500 exoplanets, according to the Christian Science Monitor. Until now, they haven't been able to determine if any exoplanets contained life.

However, recent work by Nexus for Exoplanet System Science (NExSS), synthesized by Science Daily, could be cause for optimism. The research outlines new tools and techniques that may help us answer the burning question: "Is there life beyond Earth?"

Looking for Signatures of Life

NASA formed NExSS in an effort to pool existing scientific knowledge and methods. The group includes scientists from four research communities — astrophysicists, heliophysicists, planetary scientists and Earth scientists — with the goal of "elevating the visibility and priority of exoplanet science research."

"While it is impossible to detect life directly on far away planets, we can look for tell-tale signs or 'biosignatures,'" said Carlos Niederstrasser, a master systems engineer with Northrop Grumman.

NExSS reported that there are two primary biosignatures to search for that indicate life on exoplanets: oxygen levels and color, like algae blooms or leaves, said Science Daily.

Scientists use Earth-based telescopes to make these observations. One method, said Niederstrasser, is to pass the light reflected from a planet through a spectrograph, which breaks up the light into its spectrum colors much like a prism makes a rainbow. These spectra can span not just the visual colors, but also infrared and ultraviolet wavelengths which the eye cannot naturally see. "The resulting spectra gives us an insight into what chemicals and gases are in a planet's atmosphere," he said.

Searching for Exoplanets

NASA describes the Transiting Exoplanet Survey Satellite (TESS), which launched on April 18, as, "the next step in the search for planets outside of our solar system, including those that could support life." During its mission, TESS will search for exoplanets by "surveying 200,000 of the brightest stars near the sun."

Scientists will analyze the data collected by TESS to determine which exoplanets merit further examination. TESS will then look at the planets to see if they could potentially hold signs of life, said NASA.

Don't Fall for Tricks

The search for far-off life isn't foolproof. One danger is falling for "tricks," or false indications of life. For example, planets can produce oxygen without harboring life, according to Space.com. Scientists need to think about the ways that planets can "trick" them and find other ways to identify other biosignatures.

Is There Life Beyond Earth?

The Drake Equation, named for astronomer Frank Drake, is a complex formula that provides a rough estimate for the odds of finding other forms of life in the universe, according to Space.com. More recently, NASA scientists have used the Drake Equation to determine that the odds that Earth is the only planet with life are 1 in 10 billion trillion, according to NASA.

Now here's the catch: Many of these exoplanets are thousands of light years away. That means if we do find signs of life, we can't be sure that whatever organism we're seeing is still alive. Worse, communicating directly with a far-off life form is impossible because of the time difference. In the case of the closest star to our system — Proxmia Centauri — the lag is 4.2 light-years. Proxima Centauri also hosts an Earth-like planet, according to Space.com.

The search for life on other planets continues; who knows what we will find?

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Is There Life Beyond Earth? Exoplanets May Hold the Key

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