Lisa Kaltenegger, one of the world’s leading experts on exoplanets and the potential for life beyond earth, and director of the Carl Sagan Institute at Cornell University, explains why NASA’s discovery is exciting and what life might look like on the seven Earth-like planets discovered near Trappist-1 – planets likely to have very high ultraviolet radiation flux on the surface.

Kaltenegger has two papers (“UV Surface Habitability of the TRAPPIST-1 System," currently under review at Monthly Notices of the Royal Society, and “Biofluorescent Worlds: Biological fluorescence as a temporal biosignature for flare star worlds,” forthcoming in The Astrophysical Journal) that discuss life under a very high ultraviolet radiation flux environment.


Video: Lisa Kaltenegger discusses how her team is searching for alien life,

Kaltenegger says:

“Finding multiple planets in the Habitable Zone of their host star is a great discovery because it means there can be even more potentially habitable planets per star than we thought. And finding more rocky planets in the habitable zone per star definitely increases our odds of finding life.

“Trappist-1 now holds the record for the most rocky planets in the habitable zone – our solar system only has two – Earth and Mars. Life is a definite possibility on these worlds, but it might look different because there’s likely to be very high ultraviolet radiation flux on the surface of these planets.

“How good or bad would such a UV environment be for life? Our paper, currently under review at Monthly Notices of the Royal Society, discusses just this scenario for the Trappist-1 system, examining the consequences of different atmospheres for life in a UV environment.

“We find that if the star is active, as indicated by the X-ray flux, then planets need an ozone layer to shield their surface from the harsh UV that would sterilize the surface. If the planets around Trappist-1 do not have an ozone layer (like a young Earth), life would need to shelter underground or in an ocean to survive and/or develop strategies to shield itself from the UV, such as biofluorescence.

“Atmospheric biosignatures such as methane, indicating adaptations by life, could be detected by the James Webb Space Telescope, launching in 2018, or the European Extremely Large Telescope, coming online in 2022.”

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