Is complex life in the universe a cosmic imperative or a rare phenomenon? Two researchers from Harvard say that the answer may lie within subsurface planetary oceans that never receive light, and yet, may still be able to support life.

Manasvi Lingam and Abraham Loeb released a paper on 27 November 2017 that says, “it is evident that life in the Universe has a vast range of niches that it could occupy, and worlds with subsurface oceans under ice envelopes constitute an important category.”

According to the paper’s abstract, researchers examined the prospects for life on planets with subsurface oceans, and found “that a wide range of planets can exist in diverse habitats with relatively thin ice envelopes. We quantify the energy sources available to these worlds, the rate of production of prebiotic compounds, and assess their potential for hosting biospheres. Life on these planets is likely to face challenges, which could be overcome through a combination of different mechanisms. We quantify the number of such worlds, and find that they may outnumber rocky planets in the habitable zone of stars by a few orders of magnitude.”

Lingham and Loeb conclude that “life on (exo)planets with subsurface oceans is likely to face sui generis challenges that are not prevalent on Earth. Examples include the lack of an abundant energy source equivalent to sunlight, and the possibility that the biosphere is primarily oligotrophic. On the other hand, we have not been able to identify any definitive limiters that can prevent biospheres from emerging and functioning over geologic timescales. As these worlds are likely to be far more abundant than the standard paradigm of rocky planets in the habitable zone (HZ) of stars, we suggest that more effort should focus on modeling and understanding the prospects for life in subsurface oceans.”

Earlier in 2017, the two researchers identified major challenges for the development of life in one of the most famous exoplanet systems, TRAPPIST-1.