The possibilities of finding alien life could have just gotten a big boost.
A brand new evaluation of exoplanets suggests that there’s a much greater likelihood than previously considered these worlds hosting liquid water, a necessary ingredient for all times on Earth.
The universe could due to this fact be full of more habitable planets than scientists had previously believed, with a greater likelihood of those worlds possessing environments during which alien life could develop, even in the event that they have icy outer shells.
“We all know that the presence of liquid water is crucial for all times. Our work shows that this water will be present in places we had not much considered,” research leader and Rutgers University scientist Lujendra Ojha said in a press release. “This significantly increases the probabilities of finding environments where life could, in theory, develop.”
Related: The ten most Earth-like exoplanets
Ojha and colleagues found that even exoplanets with frozen surfaces could have subsurface oceans of liquid water.
“Before we began to think about this subsurface water, it was estimated that around one rocky planet [in] every 100 stars would have liquid water,” Ojha explained. “The brand new model shows that, if the conditions are right, this might approach one planet per star. So we’re 100 times more more likely to find liquid water than we thought.”
Because there are about 100 billion stars within the Milky Way galaxy, “that represents really good odds for the origin of life elsewhere within the universe,” he added.
How icy worlds could hold on to liquid water
The researchers investigated planets found around probably the most common sort of stars in our galaxy, red dwarfs, that are smaller and cooler than the sun. Not only do red dwarfs, also often known as M-dwarfs, make up about 70% of the celebrities within the Milky Way, but also they are the celebrities around which the vast majority of Earth-like rocky worlds have been found.
The team considered two ways during which rocky planets with an icy shell may very well be heated from below, allowing them to take care of underground liquid water, the primary of which is clear here on Earth.
“As Earthlings, we’re lucky in the mean time because we’ve just the correct amount of greenhouse gases in our atmosphere to make liquid water stable on the surface. Nevertheless, if Earth were to lose its greenhouse gases, the common global surface temperature can be roughly minus 18 degrees Celsius [minus 0.4 degrees Fahrenheit], and most surface liquid water would completely freeze,” Ojha explained. “A number of billion years ago, this actually happened on our planet, and surface liquid water completely froze. Nevertheless, this doesn’t mean that water was completely solid all over the place.”
Liquid water was preserved at the moment in Earth’s history by heating in the shape of radioactivity from deep inside the planet.
“Heat from radioactivity deep within the Earth can warm water enough to maintain it liquid,” Ojha said. “Even today, we see this happening in places like Antarctica and the Canadian Arctic, where despite the frigid temperature, there are large underground lakes of liquid water, sustained by the warmth generated from radioactivity.”
The researcher said that there’s evidence to suggest that heating via radioactivity is also happening currently near the south pole of Mars.
“We modeled the feasibility of generating and sustaining liquid water on exoplanets orbiting M-dwarfs by only considering the warmth generated by the planet,” Ojha said. “We found that when one considers the opportunity of liquid water generated by radioactivity, it is probably going that a high percentage of those exoplanets can have sufficient heat to sustain liquid water — many greater than we had thought.”
One other possible heating mechanism that might help maintain liquid water below a frozen planetary shell suggested by the team arises consequently of the gravitational influence of a bigger body, causing the inside of an outwardly frozen world to endlessly churn. This can be something that is clear elsewhere in our solar system.
“A number of the moons you discover within the solar system, for instance, Europa or Enceladus, have substantial underground liquid water, though their surfaces are completely frozen,” Ojha identified, referring to icy moons of Jupiter and Saturn, respectively.
“It is because their interior is continually churned by the gravitational effects of the big planets they orbit, corresponding to Saturn and Jupiter,” he added. “This is analogous to the effect of our moon on tides but much stronger.”
Not only has this effect made Europa and Enceladus prime candidates for locating life elsewhere within the solar system, however it has implications for life-maintaining environments on worlds orbiting other stars.
NASA will soon explore a minimum of one ice world, albeit inside the bounds of the solar system: Its Europa Clipper probe is scheduled to launch toward the Jovian system in 2024 and arrive six years later.
Related: Europa Clipper: A guide to NASA’s recent astrobiology mission
Abel Méndez, director of the Planetary Habitability Laboratory on the University of Puerto Rico, was not involved in the brand new research but remarked on the implications of its findings.
“The prospect of oceans hidden under ice sheets expands our galaxy’s potential for more habitable worlds,” Méndez said. “The main challenge is to plot ways to detect these habitats by future telescopes.”
The team’s research was recently published within the journal Nature and can be presented by Ojha on the Goldschmidt geochemistry conference in Lyon, France, which is being held from Sunday (July 9) to (July 14).