Mysteries of Titan Explained

Dr. Chris McKay, a planetary scientist at NASA Ames, gave a Director’s Colloquium to students and staff on Aug. 14. The topic of McKay’s discussion was Titan, the largest moon on Saturn.

In many ways, Titan is similar to the Earth. Titan has a similar cycle with methane as Earth has to water. The spacecraft, Voyager, flew by Titan in the 1980s. Based on those images, it was assessed that Titan had an ocean. However, that doesn’t seem to be the case which they discovered when the Huygens, named after Christiaan Huygens who discovered the moon, probe landed.

There are no oceans on Titan. That has become an unsolved mystery – what is the source of methane on Titan? Oceans provide methane while sunlight destroys it. That’s the cycle. So, the source of this methane is still unknown. However, there is a theory that volcanoes provide the methane but that is not known for certain as well.

Scientists did discover from the data returned from the Huygens expedition that the air temperature of Titan has not changed in 13 years as the temperatures were very similar to the temperatures that Voyager recorded 13 years prior. It was also noted that the probe landed on wet ground because of how it landed. Interestingly, vapor came up from around the probe when it landed. Steam rose from around the probe, which would indicate that the ground was wet, most likely with methane.

There is also the question about how the channels in the equator, where it looks like rivers formerly flowed. One theory is that there are seasonal storms. However, the Titan equatoral regions of Titan do not vary with season or with day or night. So, that theory seems unlikely. The second theory is that there was a “wet age” when there was even more methane in the atmosphere. That methane isn’t currently prevalent, as it has been destroyed by sunlight.

With data returned from the Cassini spacecraft, it was discovered that there were clouds at the South Pole of Titan. However, these clouds are not there anymore. One theory for why the clouds were not there is that they are only present during solstice. With this theory, the next time we will see such strong clouds is in 15 years during the northern solstice.

The last mystery of Titan is the methane. Does methane on a planet indicate life? That remains uncertain. It would require an organism with a healthy appetite for hydrogen. Although it is possible that Titan has life, at the moment this is unknown.