Cape Canaveral, Fla. (AP) – Saturn’s giant moon Titan may not have a large underground ocean.
Titan may instead hold deep layers of ice and resemble Earth’s polar oceans, pockets of meltwater where life could possibly survive and thrive, scientists reported Wednesday.
A team led by researchers from NASA’s Jet Propulsion Laboratory challenged decades-old assumptions of a global ocean buried on Titan by taking a fresh look at observations made by NASA’s Cassini spacecraft years ago around Saturn.
They stress that no one has found any signs of life on Titan, the solar system’s second-largest moon, which is 3,200 miles (5,150 km) across and filled with lakes of liquid methane on its cold surface.
But the latest findings suggest a dense, near-melting atmosphere, “there is strong justification for continued optimism regarding the possibility of exoplanet life,” said Baptiste Jernaux of the University of Washington, who participated in the study published in the journal Nature.
Whatever form life may take, possibly strictly microscopic, “nature has repeatedly demonstrated creativity far greater than the most imaginative scientists,” he said in an email.
JPL lead author Flavio Petrica said Titan’s ocean may have frozen in the past and is currently melting, or its hydrosphere may have evolved toward complete cooling.
Computer models suggest these layers of ice, slush and water extend to a depth of more than 340 miles (550 km). The outer ice shell is thought to be about 100 miles (170 km) deep, covering pools of slush and water that may extend another 250 miles (400 km) below. This water can be as hot as 68 degrees Fahrenheit (20 degrees Celsius).
Because Titan is tidally locked, the same side of the moon always faces Saturn, like our own moon and Earth. Saturn’s gravitational pull is so intense that it distorts the moon’s surface, creating bulges as high as 30 feet (10 meters) when the two bodies are closest.
Through improved data processing, Petricca and his team managed to measure the time of peak gravitational tug and rise to Titan’s surface. If the moon held a wet ocean, the effect would be immediate, Petrica said, but a 15-hour lag was detected, indicating an icy interior with pockets of liquid water. Computer modeling of Titan’s orientation in space supported their theory.
Luciano Ice of Rome’s Sapienza University, whose previous studies using Cassini data indicated a hidden ocean on Titan, is not convinced by the latest discovery.
Although “certainly interesting and will stimulate renewed discussion … at present, the available evidence is not definitively sufficient to exclude Titan from the family of ocean worlds,” Ice said in an email.
NASA’s planned Dragonfly mission — featuring a helicopter-type craft due to launch to Titan later this decade — is expected to provide more clarity on the moon’s interior. Journaux is part of that team.
Saturn leads the list of solar system moons with 274. Jupiter’s moon Ganymede is slightly larger than Titan, with a possible underground ocean. Other suspected water worlds include Saturn’s Enceladus and Jupiter’s Europa, both of which are believed to have geysers of water from their frozen crust.
Launched in 1997, Cassini reached Saturn in 2004, orbiting the ringed planet and passing its moons until it deliberately plunged into Saturn’s atmosphere in 2017.
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