Radar piercing through the thick haze of methane surrounding Saturn?s moon Titan found some prominent landmarks had moved by as much as 19 miles in two years, NASA reported last week.
The shifts provide the first evidence of a vast underground ocean of water and ammonia, on which the moon?s crust floats.
“With its organic dunes, lakes, channels and mountains, Titan has one of the most varied, active and Earthlike surfaces in the solar system,” said Ralph Lorenz, lead author and Cassini radar scientist at the Johns Hopkins Applied Physics Laboratory in Laurel.
“Now we see changes in the way Titan rotates, giving us a window into Titan?s interior beneath the surface.”
His findings appeared Friday in the journal Science.
Lorenz?s team used Cassini?s Synthetic Aperture Radar to collect imaging data during 19 passes over Titan between October 2005 and May 2007.
The geographical changes can be explained only if the crust is not attached to Titan?s core, the researchers said.
“We believe that about 62 miles beneath the ice and organic-rich surface is an internal ocean of liquid water mixed with ammonia,” Bryan Stiles of NASA?s Jet Propulsion Laboratory, based in Pasadena, Calif., said in a statement.
Scientists are interested in Titan because its frozen surface preserves many of the chemical compounds believed to cover the Earth before human life existed.
Titan is the only moon in the solar system shrouded by a dense atmosphere and the largest of Saturn?s moons, bigger even than Mercury.
“Further study of Titan?s rotation will let us understand the watery interior better, and because the spin of the crust and the winds in the atmosphere are linked, we might see seasonal variation in the spin in the next few years,” Lorenz said.
On Tuesday, just before Cassini?s planned closest approach, 620 miles above Titan, the craft?s Ion and Neutral Mass Spectrometer will analyze Titan?s upper atmosphere.
