#Planets #Scientists – Scientists have a new way to determine which alien planets could truly be habitable : A new study suggests that when it comes to finding habitable planets that could support alien life, there may be far fewer suitable worlds than we previously thought.
According to the research, current estimates of planetary habitability based on the so-called Goldilocks zone – being the right distance from the Sun to sustain life – don’t take into account another crucial factor needed for life to exist on a planet: the internal temperature when the world formed.
The problem isn’t so much with the Goldilocks zone itself, says geophysicist Jun Korenaga from Yale University, but with our understanding of how planets regulate their temperature by a process called mantle convection.
To backtrack a little, planets within the Goldilocks zone of a star are considered potentially habitable because they’re the right distance from their sun for liquid water to exist on their surface.
Basically, these planets can’t be so far away from their sun that any liquid water necessary to sustain life would freeze, but they also can’t be too close, because then the star’s intense heat would make the water evaporate.
So the potential for liquid water to exist on a planet’s surface is strongly related to the planet’s surface temperature.
But there’s another factor that can influence a planet’s surface temperature – mantle convection.
This describes how underground tectonic movements alternately heat and cool the internal temperature of a planet, as rocks shift around, dispersing or containing heat.
Scientists used to think that most planets were capable of self-regulating their temperature in this way, which could lead to some worlds settling upon the right temperature to sustain life.
But that’s where Korenaga’s new study suggests we might be mistaken, finding that the initial internal temperature of the planet when it first forms has a far greater influence on its potentially habitability than any self-regulation that goes on afterwards.
“If you assemble all kinds of scientific data on how Earth has evolved in the past few billion years and try to make sense out of them, you eventually realise that mantle convection is rather indifferent to the internal temperature,” he says.
Using a new mathematical framework to calculate how this self-regulation works, Korenaga suggests that Earth-like planets are unlikely to affect their own internal temperatures in this way, meaning the right conditions for habitability – in addition to the world falling within the Goldilocks zone – depend upon the initial temperature of the world when it first forms.
“Studies on planetary formation suggest that planets like Earth form by multiple giant impacts of cosmic matter, and the outcome of this highly random process is known to be very diverse,” explains Korenaga.