Saturn's moon resembling Death Star could potentially house an extensive subterranean ocean.

Astronomers have uncovered the strongest indication yet of a substantial, young ocean hidden beneath the icy shell of Saturn's mini-moon, which bears striking resemblance to the Death Star from Star Wars.

The research, led by a French team, scrutinized variations in the orbit and rotation of Mimas and concluded on Wednesday that a concealed ocean 20 to 30 kilometers deep under the icy surface is more plausible than an elongated rocky core. Their conclusion relies on data collected by NASA's Cassini spacecraft, which examined Saturn and its plethora of over 140 moons for over a decade before plunging into Saturn's atmospheric layer in 2017 and disintegrating.

Despite its mere 400 kilometers in diameter, the heavily cratered moon lacks the usual indicators of subsurface activity like fractures and geysers, a typical sight on Saturn's Enceladus and Jupiter's Europa.

Valery Lainey of the Paris Observatory, one of the co-authors of the research, shared in an email that Mimas was perhaps the least expected place to find a global ocean and, more broadly, liquid water. He suggested that this discovery makes Mimas an interesting world potentially capable of supporting life, though the required timespan for life to emerge remains unknown.

The findings were published in the respected journal Nature.

Lainey estimates the ocean to make up half of Mimas' volume, yet due to the moon's small size, it only accounts for between 1.2% and 1.4% of Earth's ocean volume. Although Mimas is relatively small, it is home to the second largest impact crater of any moon in the solar system, which has led to the comparison with the fictional Death Star from the "Star Wars" films.

Matija Cuk of the SETI Institute and Alyssa Rose Rhoden from the Southwest Research Institute, both non-participants in the study, commented in an associated editorial that, "The concept that small, icy moons may contain young oceans is truly fascinating."

The underground ocean is thought to be between 5 million and 15 million years old, which makes it too young to have left any marks on the surface of the moon. Its overall temperature hovers around freezing, according to Lainey, although it might be considerably warmer at the seafloor.

Co-author Nick Cooper from Queen Mary University of London stated that given its relatively young age, the discovery of an ocean of liquid water on Mimas makes it a top contender for studying the origins of life.

Named after a giant from Greek mythology, Mimas was discovered by English astronomer William Herschel in 1789.