January 14, 2005, was a milestone in space science history. On this day the Huygens probe made a perfect landing on Titan revealing its surface for the first time. The Cassini-Huygens mission will orbit Saturn for four years and has already sprung a few surprises.
Titan began to generate interest in the early 1900s, when astronomer Comas Sola, reported specks that looked like atmospheric clouds. The presence of an atmosphere was confirmed when Kuiper analysed sunlight reflected from Titan. During the 1970s and 1980s both Pioneer 11 and Voyager spacecrafts flew by Titan. Voyager’s data revealed that Titan had organic compounds in its atmosphere.
Why study Titan?
Why is there such a lot of interest in a satellite, which is almost a billion kilometres away? Titan is not just any moon! Scientists have detected many similarities between earth and Titan.
Atmosphere: Titan’s atmosphere is like pre-life earth before living organisms started to pump oxygen into it. It is nitrogen-rich like ours, but is 10 times thicker. It is also rich in organic material – like ethane, propane, acetylene, and others.
Weather systems: Kuiper’s analysis revealed that Titan also has methane and this led to many theories. Among the popular ones is that methane on Titan plays the role of water on Earth – it rains out of clouds, forms into rivers which feed oceans and evaporates to form clouds again. Just like Earth’s water cycle! Are there oceans of methane on Titan? Many scientists believed so.
Lessons to learn
Titan is a time vault – much like a young earth. While Mars is considered to be a later version of Earth where life perhaps disappeared, many experts think Titan is a primordial earth where life may yet evolve. Compounds discovered in Titan’s atmosphere are very similar to those present on earth 4.6 billion years ago. When the atmosphere is so much like early earth, isn’t it possible that the surface will have clues about the building blocks of life? A detailed study of Titan’s surface has never been possible because the thick atmosphere hung like a veil over the moon. Now for the first time the Cassini mission is coming up with some answers.
On a mission
The mission has overturned previous assumptions and thrown up new surprises. The first was when Huygens failed to find methane rivers or oceans. But it found a landscape scoured by floods. While the search for oceans is still on, their absence puzzled scientists as the scoured surface indicates to the presence of liquids.
The answer may lie in the latest find. Cassini spotted a volcano-like dome that scientists are calling cryovolcano. They explain that these may spew out a mixture of water, methane and ammonia. The methane may collect in the atmosphere and periodically fall as methane rain, which would create short-lived channels that eventually dry up. So is that one mystery solved?Hey! Hold your breath! Who knows what Cassini finds next in the mysterious Titan...