A key discovery from NASA’s Cassini mission in 2008 was that Saturn’s largest moon Titan may have a vast water ocean below its hydrocarbon-rich surface. But reanalysis of mission data suggests a more complicated picture: Titan’s interior is more likely composed of ice, with layers of slush and small pockets of warm water that form near its rocky core.
Led by researchers at NASA’s Jet Propulsion Laboratory in Southern California and published in the journal Nature on Wednesday, the new study could have implications for scientists’ understanding of Titan and other icy moons throughout our solar system.
“This research underscores the power of archival planetary science data. It is important to remember that the data these amazing spacecraft collect lives on so discoveries can be made years, or even decades, later as analysis techniques get more sophisticated,” said Julie Castillo-Rogez, senior research scientist at JPL and a coauthor of the study. “It’s the gift that keeps giving.”
To remotely probe planets, moons, and asteroids, scientists study the radio frequency communications traveling back and forth between spacecraft and NASA’s Deep Space Network. It’s a multilayered process. Because a moon’s body may not have a uniform distribution of mass, its gravity field will change as a spacecraft flies through it, causing the spacecraft to speed up or slow down slightly. In turn, these variations in speed alter the frequency of the radio waves going to and from the spacecraft — an effect known as Doppler shift. Analyzing the Doppler shift can lend insight into a moon’s gravity field and its shape, which can change over time as it orbits within its parent planet’s gravitational pull.
This shape shifting is called tidal flexing. In Titan’s case, Saturn’s immense gravitational field squeezes the moon when Titan is closer to the planet during its slightly elliptical orbit, and it stretches the moon when it is farthest. Such flexing creates energy that is lost, or dissipated, …
