Researchers said that evidence of opportunities for obtaining liquid water from Earth-like planets from outside the solar system suggests that the number of these planets exceeds the previously estimated numbers, an increase of up to 100% over previous estimates, which increases the chances of finding life on these planets.
In the study, the results of which were presented on July 10 at the Goldschmidt Conference of European and American geochemists, in the French city of Lyon, the researchers found that even when conditions are not ideal for the presence of liquid water on the surface of a planet, many stars will have the appropriate geological conditions to liquefy water under the surfaces of these planets.
The analysis included planets around the most common type of star, suns called M-dwarfs, meaning cool or red stars, which are mostly dwarf stars with a surface temperature of less than 3,500 K (colder than our Sun) and a mass less than half that of the Sun in our Milky Way galaxy. The researchers found that even if the planet’s surface had frozen over, there were two main ways in which enough heat could be generated to allow water to turn into a liquid state below the planet’s surface.
“We know that liquid water is essential for life. Our work shows that this water can be found in places we haven’t thought much about. This greatly increases the chances of finding environments in which life could theoretically evolve,” says the study’s principal investigator, Lochendra Uiga, assistant professor of earth sciences at Rutgers University.
Ouiga added, in a statement to The New Arab: “We, the inhabitants of planet Earth, are fortunate to have the right amount of greenhouse gases in our atmosphere to make liquid water stable on the surface. However, if the Earth loses greenhouse gases, the average surface temperature of the Earth will be around minus 18 degrees Celsius, and most of the liquid surface water will freeze completely. This actually happened a few billion years ago, when liquid water completely froze over most parts of the planet.”
The researcher noted that arriving at the results required modeling the feasibility of generating and maintaining liquid water on exoplanets orbiting M-dwarfs by looking only at the heat generated by the planet. The research team found that when taking into account the possibility of liquid water resulting from radioactivity, this suggests the possibility of a high percentage of exoplanets, which could have enough heat to maintain liquid water.
Previously, scientists believed that out of all the rocky planets orbiting 100 stars (the sun), only one rocky planet contains liquid water, but the new study has raised these estimates a lot to one planet per star, an increase of 100% from previous estimates.
Regarding the role of geothermal heat in facilitating the presence of liquid water on the surface of the planet, the researcher explains that the heat resulting from radioactivity in the depths of the earth can heat the water enough to keep it liquid. “Even today, we see this happening in places like Antarctica and the Canadian Arctic, where there are large underground lakes of liquid water that, despite freezing temperatures, feed on heat from radioactivity. There is even some evidence that this might be happening now at the south pole of Mars,” Ouiga says.
Some of the moons in the solar system, such as Europa, contain a large amount of ground liquid water, even though their surfaces are completely frozen. The authors attribute this to the fact that the interior of these moons is constantly oscillating through the gravitational effects of the large planets that orbit them, such as Saturn and Jupiter. This is similar to the effect of the moon on tides, but it is much stronger, which makes the moons of Jupiter and Saturn prime candidates for life in our solar system.
