More Exoplanets May Be Suitable For Life Than Previously Thought

Far more exoplanets (planets located outside of the Solar System) may have the ingredients for life than scientists currently give credit.

This is the argument theoretical physicist Sara Seager of the Massachusetts Institute of Technology lays out in a provocative review article published in the journal Science.

The basic premise scientists currently hold is that, in order to support life, a planet must have liquid water, which largely depends on the planet’s temperature.

However, as Seager points out in her article “Exoplanet habitability,” while planets with thin atmospheres rely on heating from their stars, the primary control of surface temperature for many planets is the greenhouse effect.

A planet ten times farther from their stars than Earth is from the Sun, for instance, could actually boast liquid water and thus life if, for example, its atmosphere had enough hydrogen gas.

“It’s really all about the greenhouse gases,” Seager told Space.com. “The greenhouse gases are like a blanket that moderates the temperature at the surface.”

In fact, Seager argues, a planet may not even have to orbit a star at all should it generate enough heat by processes occurring in its core, and so long as it is home to enough atmospheric gases to keep that warmth.

“If there is one important lesson from exoplanets, it is that anything is possible within the laws of physics and chemistry,” Seager wrote in the article. “Planets of almost all masses, sizes and orbits have been detected, illustrating not only the stochastic nature of planet formation but also a subsequent migration through the planetary disk from the planet’s place of origin.”

Going forward, Seager said scientists plan to use the Transiting Exoplanet Survey Satellite, which NASA recently approved for a 2017 launch, to identify promising candidates close to Earth, which will then be followed by the James Webb Space Telescope for an in-depth look at the planets’ air.

Ultimately, Seager told Space.com, her hope in publishing the article is to help “people to realize that so many types of worlds could be habitable, and that our chance of finding one is higher when we accept that.”