A recent analysis presented at the Goldschmidt geochemistry conference in Lyon suggests that there may be a higher probability of finding Earth-like exoplanets with liquid water than previously thought. The study reveals that even if the conditions on the surface of a planet are not ideal for liquid water, there may still be geological conditions beneath the surface that can support it.
Lead researcher Dr. Lujendra Ojha from Rutgers University explains that the presence of liquid water is crucial for the development of life. The research shows that water can exist in unexpected places, increasing the chances of finding environments where life could potentially thrive.
The researchers discovered that even if a planet’s surface is frozen, there are two main ways in which enough heat can be generated to allow for liquid water underground. Dr. Ojha explains that Earth is currently fortunate to have the right amount of greenhouse gases in its atmosphere to keep liquid water stable on the surface. However, if Earth were to lose these greenhouse gases, the average global surface temperature would drop to approximately -18 degrees Celsius, causing most surface water to freeze. This happened billions of years ago on Earth, but it doesn’t mean that all water became solid. Radioactivity deep within the Earth can generate enough heat to keep water liquid, as seen in places like Antarctica and the Canadian Arctic. There is even evidence suggesting that this may be happening currently at the south pole of Mars.
Dr. Ojha also mentions that some moons in our solar system, such as Europa and Enceladus, have significant amounts of underground liquid water despite their frozen surfaces. This is due to the gravitational effects of the large planets they orbit, which continuously churn their interiors. These moons are considered prime candidates for finding life within our solar system, and future missions have been planned to explore them.
The analysis focused on planets orbiting M-dwarfs, which are small and colder stars compared to our Sun. M-dwarfs make up 70% of the stars in our galaxy, and most of the rocky and Earth-like exoplanets discovered so far orbit these stars. The researchers modeled the feasibility of generating and sustaining liquid water on these exoplanets by considering only the heat generated by the planet itself. However, when they also considered the possibility of liquid water generated by radioactivity, they found that a higher percentage of these exoplanets could have enough heat to sustain liquid water.
Previously, it was estimated that only around 1 rocky planet per 100 stars would have liquid water. However, the new model suggests that if the conditions are right, this number could increase to 1 planet per star. This means that the chances of finding liquid water are a hundred times higher than previously thought. With approximately 100 billion stars in the Milky Way Galaxy, these findings provide promising odds for the existence of life elsewhere in the universe.