The scientific community is currently reevaluating its understanding of where life could potentially exist beyond Earth. This comes after a study led by Cornell University scientists, which suggests that an abundance of life-bearing planets could orbit stars smaller than the sun, contrary to previous beliefs.
Traditionally, scientists have focused their search for extraterrestrial life on planets that exist within a star’s “habitable zone” – the region around a star where conditions could theoretically allow liquid water, and thus life, to exist on a planet’s surface. This habitable zone is also referred to as the ‘Goldilocks Zone’ because conditions are neither too hot nor too cold, but just right for life as we know it.
The study, however, turns this conventional wisdom on its head. The Cornell-led team proposes the concept of the “subhabitable zone,” a region around a star where subsurface life could exist below a planet’s icy shell, similar to Jupiter’s moon Europa and Saturn’s moon Enceladus in our own solar system. This is a significant shift in thinking, as it moves the focus from the surface of planets to their subsurface, where life could potentially survive in liquid water below a protective layer of ice.
The team argues that considering a planet’s subsurface conditions expands the potential habitable zones to include planets that orbit smaller, cooler stars. These stars, known as K- and M-type stars, are the most common in the Milky Way galaxy. According to the study, planets orbiting such stars could maintain subsurface oceans for billions of years due to the stars’ long lifetimes, increasing the chances of life developing and evolving.
The study also indicates that a significant number of planets around these stars could have the right conditions for subsurface life, far more than previously thought. This expands the number of potential “biosignatures” – signs of life – that future space missions could detect.
This new perspective on habitability may have significant implications for future space missions. It potentially broadens the scope of planets and moons that missions, such as NASA’s upcoming James Webb Space Telescope (JWST), could study for signs of life. This could revolutionize our understanding of where life could exist in the universe, and possibly bring us one step closer to discovering extraterrestrial life.
The findings of the study are published in the Monthly Notices of the Royal Astronomical Society.
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