14 DAY TRIAL // Saturn's satellite, Titan, is 50 percent larger than our Moon in diameter, and it's even larger by diameter and mass than all known dwarf planets, like Mercury, even though the latter is more than twice as massive.
One of the satellite's curiosities is a strange radio signal emitted at an extremely low frequency, detected by the European Space Agency's Huygens probe as it descended to the moon's surface after being jettisoned from the Cassini spacecraft in 2005.
So far, no one has been able to pinpoint the origin and what causes this signal, since the only other world on which ELF waves were detected before was Earth.
According to a team of scientists, the weird radio signal could be coming from an underground ocean of liquid water, much like the one under the 15-mile-thick ice crust on another satellite of Jupiter, Europa.
Since water is the key component for life, if such an ocean were to exist beneath Titan's surface, the possibility of lifeforms existing in that ocean could not be denied. It is generally believed that the surface of Titan is a thick crust of ice, kept rock hard by the prevailing surface temperature of -178? Celsius.
Now, Fernando Simoes of the Centre d'Etudes Terrestres et Planetaires in Saint Maur, France, and his colleagues, claim to have the first observational evidence of such an ocean, thus confirming theoretical models, which predicted that ammonia-rich water deep beneath the surface could stay liquid, perhaps forming a global ocean.
The only other place where such a signal has been detected is Earth, where lightning causes an echo effect, bouncing radio waves back and forth between the ground and the upper layers of our atmosphere.
But the ice at the surface of Titan is a poor reflector of radio waves, so if the signal comes from an echo effect like that on Earth, there would have to be a more reflective material below the surface, and an underground ocean will produce exactly the same effect.
"We do not need a subsurface ocean but require a subsurface reflector," said Simoes. "If a subsurface ocean exists, the solid-liquid interface would be a good reflector."
So far, no one has been able to rule out this explanation, as it happened with other probable causes that were eventually dismissed (no lightning has been detected on Titan so far; laboratory experiments with copies of the instruments on board the probe ruled out interferences from other parts of the probe).