Saturn's giant moon Titan may not have a vast underground ocean after all. Titan instead may hold deep layers of ice and slush more akin to Earth's polar seas, with pockets of melted water where life could possibly survive and even thrive, scientists say. A team led by researchers at NASA's Jet Propulsion Laboratory challenged the decade-long assumption of a buried global ocean at Titan after taking a fresh look at observations made years ago by NASA's Cassini spacecraft around Saturn, the AP reports.
They stress that no one has found any signs of life at Titan, the solar system's second largest moon, after Jupiter's Ganymede, spanning 3,200 miles and brimming with lakes of liquid methane on its frosty surface. But with the latest findings suggesting a slushy, near-melting environment, "there is strong justification for continued optimism regarding the potential for extraterrestrial life," said the University of Washington's Baptiste Journaux, who took part in the study published in the journal Nature. As to what form of life that might be, possibly strictly microscopic, "nature has repeatedly demonstrated far greater creativity than the most imaginative scientists," he tells the AP.
JPL's Flavio Petricca, the lead author, said Titan's ocean may have frozen in the past and is currently melting, or its hydrosphere might be evolving toward complete freezing. Computer models suggest these layers of ice, slush, and water extend to a depth of more than 340 miles. The outer ice shell is thought to be about 100 miles deep, covering layers of slush and pools of water that could go down another 250 miles. This water could be as warm as 68 degrees Fahrenheit. Because Titan is tidally locked, the same side of the moon faces Saturn all the time, just like our own moon and Earth. Saturn's gravitational pull is so intense that it deforms the moon's surface, creating bulges as high as 30 feet when the two bodies are closest.
Through improved data processing, Petricca and his team managed to measure the timing between the peak gravitational tug and the rising of Titan's surface. If the moon held a wet ocean, the effect would be immediate, Petricca said, but a 15-hour gap was detected, indicating an interior of slushy ice with pockets of liquid water. Computer modeling of Titan's orientation in space supported their theory.
- Luciano Iess at Sapienza University of Rome, whose previous studies using Cassini data indicated a hidden ocean at Titan, is not convinced by the latest findings. While "certainly intriguing and will stimulate renewed discussion ... at present, the available evidence looks certainly not sufficient to exclude Titan from the family of ocean worlds," he tells the AP.
- 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 innards. Journaux is part of that team.
- Saturn leads the solar system's moon inventory with 274. Jupiter's Ganymede is just a little 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 erupting from their frozen crusts.
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