Titan is Saturn's largest moon and the second largest natural satellite in the Solar System. It was of great interest to NASA, since its dense atmosphere made it difficult to determine what its surface would look like. However, the climate, including wind and rain, creates features that include dunes, rivers, lakes and seas, prompting many to believe that it bears similarities to the Earth.
Professor Brian Cox revealed how NASA sent a probe to explore Titan in 1997 during his new BBC series "The Planets."
He said in the first episode that aired on May 28: "Among all those moons there is one above all others that we think might have the best chance of becoming a place that we recognize.
"Out in the cold and far reaches of the Solar System, past Jupiter, around the planet of Saturn orbits a gem.
"Titan – a moon the size of a planet larger than Mercury surrounded by a thick atmosphere of nitrogen and methane with a surface that has long remained a mystery.
"The Huygens probe was our first chance to explore under the clouds and its camera sent back those first glimpses of the distant moon.
"Wonderfully, the ship made a soft landing and continued to convey what it saw."
Dr. Cox then lifted a photograph of Titan's surface and revealed how it reached near -200C temperatures.
He explained, "This is a wonderful photograph and the more you know about it, the more wonderful it gets.
"This is a photograph of the surface of the moon orbiting a planet more than a billion kilometers away.
"So we have a camera on the surface of a world and what you see here is something that looks like a floodplain or a riverbed.
"These rocks have been softened and corroded by the liquid and we know that these are, in fact, boulders of frozen water.
"They are frozen solid because the temperature on the surface of this moon is -180C."
However, Dr. Cox explained how, on closer inspection, NASA scientists were surprised by what they found.
He added: "Huygens has detected a significant amount of methane – a flammable gas on Earth.
"But the relatively high atmospheric pressure and the cold temperature on Titan's surface mean that this methane exists as a liquid.
"Titan could be wet, not with water, but with liquid methane driving rocky chunks of ice in the canals of the mountains and open flood plains.
"Oxygen survived for only a few hours, but it did not detect any traces of liquid methane at its landing site."
During the same series, Dr. Cox also revealed how NASA discovered a "secret" on the planet Mercury after sending its MESSENGER (Mercury Surface, Space Environment, Geohemistry and Ranging) probe in 2004.
He said: "MESSENGER approached Mercury at such a high speed that it was forced to fly three times on the planet, slowing down at every pass.
"Until almost seven years of seamless navigation, it arrived safely in orbit.
"MESSENGER defined his mission to map the surface of Mercury.
"He began to reveal the secrets of the most cratered planet in the Solar System in new details."
The probe also recorded chemical elements in concentrations never seen before.
Scientists did not expect to find such compositions on a planet so close to the sun today, since they usually disappear easily.