There are a hundred times more planets and moons with flowing water than previously thought meaning the cosmos could be teeming with alien life.
Earth-like alien worlds are dotted across the universe and many have the right geological conditions for underground oceans and lakes – when conditions above are too cold.
The findings increase the probability of discovering extra-terrestrial water a hundredfold, say the US team.
They are based on an analysis of small stars called M-dwarfs – the most common type which are much colder than our Sun.
Lead author Dr Lujendra Ojha, of Rutgers University in New Jersey, said: “We know the presence of liquid water is essential for life.
“Our work shows this water can be found in places we had not much considered. This significantly increases the chances of finding environments where life could, in theory, develop.”
The study found that even if the surface of a planet is frozen there are two main ways that enough heat can be generated to allow water to liquify below.
Dr. Ojha said: “As Earthlings, we are lucky at the moment because we have just the right amount of greenhouse gases in our atmosphere to make liquid water stable on the surface.
“However, if Earth were to lose its greenhouse gases, the average global surface temperature would be approximately -18 degrees Celsius – and most surface liquid water would completely freeze.
“A few billion years ago, this actually happened on our planet and surface liquid water completely froze.
“However, this doesn’t mean that water was completely solid everywhere. For example, heat from radioactivity deep in the Earth can warm water enough to keep it liquid.
“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 heat generated from radioactivity.
“There is even some evidence to suggest that this might be even happening currently in the south pole of Mars.”
The study is a big tonic for alien hunters. The Milky Way alone has around 100 billion stars – each with at least one orbiting planet. Millions are in the “Goldilocks zone” where water is liquid.
Dr. Ojha said: “Some of the moons you find in the solar system – for example, Europa or Enceladus – have substantial underground liquid water, even though their surfaces are completely frozen.
“This is because their interior is continually churned by the gravitational effects of the large planets they orbit, such as Saturn and Jupiter.
“This is similar to the effect of our Moon on tides but much stronger. This makes the moons of Jupiter and Saturn prime candidates for finding life in our Solar System and many future missions have been planned to explore these bodies.”
About 70 percent of stars in our galaxy are M-dwarfs – and most rocky and Earth-like exoplanets found to date orbit them.
Dr. Ojha said: “We modeled the feasibility of generating and sustaining liquid water on exoplanets orbiting M-dwarfs by only considering the heat generated by the planet.
“We found when one considers the possibility of liquid water generated by radioactivity, it’s likely a high percentage of these exoplanets can have sufficient heat to sustain liquid water – many more than we had thought.
“Before we started to consider this sub-surface water, it was estimated around one rocky planet every 100 stars would have liquid water.
“The new model shows if conditions are right, this could approach one planet per star. So we are a hundred times more likely to find liquid water than we thought.
“There are around 100 billion stars in the Milky Way Galaxy. That represents really good odds for the origin of life elsewhere in the universe.”
The earliest mission to an icy moon will be NASA’s Europa Clipper due to launch in 2024 – and arrive at Jupiter’s moon in 2030.
Professor Abel Mendez, of the Planetary Habitability Laboratory at Puerto Rico University, who was not involved in the study, said: “The prospect of oceans hidden under ice sheets expands our galaxy’s potential for more habitable worlds.
“The major challenge is to devise ways to detect these habitats by future telescopes.”
Many worlds beyond the solar system could soon be within the grasp of our technology.
More than 4,000 have been discovered so far. NASA satellite TESS is expected to multiply the number dramatically in the next decade.
Produced in association with SWNS Talker
Edited by Saba Fatima and Asad Ali
