A multitude of potentially habitable moons

When we think of astrobiology within our Solar systemwe usually think of March. The Red Planet, close to the Earth, sheltered in the past water in the state liquid on its surface, making it an ideal candidate for the search for extraterrestrial life. But scientists are increasingly turning to the study of moons outer solar system: some, likeEurope – moon of Jupiter – or ofEnceladus – moon of Saturn – are suspected of harboring a liquid internal ocean, which could potentially harbor life, thus pushing the search for extraterrestrial life outside the living area of one star system.

Gravitational interactions to warm the interior of the moons?

To understand the mechanisms that come into play to form a liquid ocean within a body far from its star, we can take the example of Europa, a satellite of Jupiter. Here theenergy solar energy is far too weak to maintain liquid water there, yet scientists strongly suspect the presence of a internal ocean. According to the researchers, it would be the gravitational interactions between the moon and its host planet, Jupiter, which would make it possible to generate movements in the interior of Europe, and thus to maintain a sufficiently high temperature under the surface of the moon to form a layer of liquid water there: this is what is called the heating by effect of tide.

Considering the relatively large number of moons likely to harbor an inner ocean in our Solar System alone, scientists consider the chances of observing similar multilunar systems elsewhere in our Galaxy are quite high, pushing back the search for signs ofexobiology beyond the habitable zone of a star system. In their studythe scientists point out that within multilunar systems, the resonances orbital – for example when the orbital period of a moon around its host planet is twice that of a second – between different moons could increase tidal heating phenomena. In some cases, these resonance phenomena could increase the eccentricity of a moon, also increasing the warming effects. In the models used in the study, tidal heating can, in the most extreme theoretical case, warm the interior of a moon by more than 200°C, for a moon orbiting a exoplanet terrestrial type in two to four days.

Gravitational interactions to stabilize a system?

But the gravitational interactions between two bodies can have other apps for the habitability of a system. In a better-known case, scientists suggest that the formation of the Moon played a crucial role in the appearance of life on Earth, by stabilizing the tilt axial of our planet, allowing the appearance of a regular seasonal cycle. The heating induced by the interactions between the two bodies also has a role to play in the movements within the earth coregenerating the magnetic field who protects us from cosmic raysand which protects our atmosphere of the solar winds. Thus, the gravitational interactions between a planet and its moons have effects on the habitability of both the moons and the planet.

These results have important applications in the search for life outside our solar system, now including the search for exomoons, which are very difficult to find. According to the authors of the study, the effects induced by the gravitational interactions between an exoplanet and its potential moons could on the other hand be visible, making the detection of exomoons potentially easier.