A new analysis shows that there are probably many more exoplanets similar to Earth with liquid water than previously thought. The work reveals that even where conditions are not ideal for the existence of liquid water on the surface of a planet, water could be present beneath the planet’s surface.

Presenting the work at the Goldschmidt geochemistry conference in Lyon, lead researcher Dr. Lujendra Ojha (Rutgers University, New Jersey, USA) stated: “We know that the presence of liquid water is essential for life. Our work shows that this water can be found in places we had not considered sufficiently before. This significantly increases the chances of finding environments where life could theoretically develop.”

Researchers have discovered that even if the surface of a planet is frozen, there are two main ways to generate enough heat to allow water to liquefy underground. Lujendra Ojha said: “As Earthlings, we are currently fortunate because we have the right amount of greenhouse gases in our atmosphere to keep water stable in a liquid state on the surface. However, if Earth were to lose its greenhouse gases, the global average surface temperature would be about -18 degrees Celsius, and most of the surface water would freeze completely. Billions of years ago, this actually happened on our planet, and the surface water completely froze. However, this does not mean that the water was completely solid everywhere. For example, the heat from radioactivity in the depths of the Earth could heat the water enough to keep it liquid. Even today, we see it happening in places like Antarctica and the Canadian Arctic, where despite freezing temperatures, there are large underground lakes, sustained by the heat generated by radioactivity. There is also some evidence to suggest that this could be the case currently at the South Pole of Mars.”

Dr. Ojha continued: “Some of the moons found in the solar system (such as Europa or Enceladus) have significant amounts of liquid water underground, even though their surfaces are completely frozen. This is because their interiors are constantly stirred by the gravitational effects of the large planets around which they orbit, like Saturn and Jupiter. A similar effect to our Moon’s influence on tides, but much stronger. This makes Jupiter and Saturn’s moons the prime candidates for finding life in our solar system, and many future missions are planned to explore these celestial bodies.”

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