A new study reveals that at least six moons of the solar system could harbor large oceans of liquid water beneath their icy surfaces. Among them are Europa, Ganymede, Callisto, Enceladus, Titan, and Mimas, while Triton and several satellites of Uranus remain under investigation.
Hidden oceans on moons of the solar system
This discovery has revolutionized the search for habitable environments beyond our planet. Historically, scientists focused their efforts on planets located at the right distance from the Sun to maintain water in liquid form on the surface. However, some of the most promising locations are found in the colder and more distant corners of the solar system.
The evidence of these oceans does not come from direct images but from magnetic signals, gravitational measurements, orbital variations, rotation, and chemical analyses. For example, Enceladus ejects materials into space, while Callisto’s ocean is inferred from magnetic data.
NASA uses the term “ocean world” to refer to celestial bodies with a considerable amount of liquid. This water may be covered by ice and contain different compounds such as salts or ammonia, which help it remain in a liquid state.
Gravitational interaction with giant planets can stretch and compress the moons, generating internal heat in a process known as tidal heating. This phenomenon, along with radioactive decay and the presence of substances like salts and ammonia, helps maintain the water in liquid form.
Europa, one of Jupiter’s moons, is covered with young ice and shows fractures suggesting the presence of a salty ocean. This could contain more water than all of Earth’s oceans combined and be in contact with a rocky seabed, which would favor chemical reactions that could support life.
Ganymede, the largest moon in the solar system, has its own magnetic field. Variations in its auroras indicate the possible existence of an ocean beneath its surface. In Callisto, although the evidence is less direct, measurements suggest the presence of an ocean beneath a thick layer of ice.
In Enceladus, active geysers have allowed space probes to directly study the expelled water. These studies have found particles of salty ice and organic compounds. Titan presents liquid methane on its surface and a subsurface ocean that could begin 50 kilometers beneath the ice.
A surprising case is that of Mimas, a small moon of Saturn that could have a global ocean at a depth of 20 to 30 kilometers. This ocean could be geologically young, which would explain the lack of observable activity on the surface.
Upcoming missions, such as NASA’s Europa Clipper and the European Space Agency’s Juice, will head towards Jupiter. These missions will seek to clarify the depth and composition of these oceans, providing crucial data on the possibility of extraterrestrial life on these moons.
