Unlike Earth, there are millions of planets whose permanent day sides are bathed in stellar light and their permanent night sides are shrouded in darkness. The region between these two sides is called the “Terminator Zone” and is a logical place to look for other life in the galaxy, new research says.
Many planets are tidally locked to the Sun, much like the Moon is to Earth. That is, it takes the same amount of time for the planet to orbit the sun. This causes the planet to always show the same side to the Sun, resulting in a permanent bright side and a permanent dark side. The day side is scorching hot with no liquid water left, the nights are unimaginably cold, and the liquid water is solid and frozen, making neither side suitable for life.
But between these two extremes lies a land shrouded in eternal twilight known as the Terminator Zone, where temperatures and conditions are just right for liquid water—life. Or so say astronomers at the University of California, Irvine (UCI).
In reaching their conclusions, the researchers modified software commonly used to study Earth’s climate. This involved slowing the planet’s rotation to mimic a tidally locked planet. They believe their discoveries could probe an entirely new group of planets as astronomers search for planets with the right conditions to harbor life. There are many planets to study, as they are found around relatively faint M-type dwarfs, which make up about 70% of the stars visible from Earth.
Lead scientist and postdoc Anna Lobo said: “We are looking at more water-restricted planets that may have lakes and other small bodies of liquid water, even though the oceans are not extensive. I’m trying to draw your attention, these climates can actually be very promising, researchers from the UCI Department of Physics and Astronomy.
Lobo and her colleagues believe that the most likely Terminator Zone targets are on land-based exoplanets rather than watery planets, which are more likely to be covered by steam.
“Ana showed that a scenario called ‘Terminator Habitability’ could exist much more easily if there was a lot of land on Earth,” said an associate professor of physics and astronomy at the UCI. Study co-author Aokawa Shields said, “These new and exotic habitability states that our team is uncovering are no longer science fiction stories. Ana believes that such states are We did our job to show that it could be climatically stable.”
The discovery could have implications for how astronomers look for biosignatures of life. Because biosignatures for life may not be present throughout a planet’s atmosphere, but rather in fairly thin slices. The study is also consistent with previous work that has shown that air circulation between cold and hot sides of tidally locked planets can create a life-supporting atmosphere.
A paper on this research is Journal of Astrophysics.
Source: UCI News
