New Delhi: There are only 90 impact craters identified on Titan, the ice moon in orbit around Saturn. Most of the other moons in the Solar System, including our own have pockmarked surfaces. The impact craters on Titan are also hundreds of metres shallower than expected. Researchers used sophisticated computer modelling to determine how the topography of Titan can relax and rebound after an impact event. The scientists were able to determine that a global layer of insulating methane clathrate ice, or water ice with methane gas trapped within the crystals, surrounds Titan. The scientists were able to calculate that this methane-water ice layer was between five and ten kilometres in thickness.
The proposed internal structure of Titan. (Image Credit: SOEST).
A paper describing the research has been published in The Planetary Science Journal. The methane ice shell can help explain the origin of the methane-rich atmosphere on Titan, as well as the carbon cycle on the ice moon. This is a hydrological cycle based on liquid methane. The surface of Titan is so cold that gases on Earth are liquids on the ice moon. There are hydrocarbon lakes and seas, with methane icebergs, and even waves. Titan is the only Solar System body other than Earth with liquids on the surface. Titan also has a thick, methane atmosphere, all of which make Titan a prime candidate to focus the search for extraterrestrial life.
Exotic life in Titan
There can actually be two forms of life on Titan. The global liquid water subsurface ocean can host carbon-based life forms more similar to the ones found on Earth. The surface though, an exotic form of life can exist that use ethane or acetylene for metabolic processes as against glucose on Earth. This as-yet hypothetical form of biochemistry would use liquid hydrocarbons as solvents as against water used by all organisms on Earth. These lifeforms would have to derive energy from chemical reactions instead of depending on photosynthesis. NASA is sending the Dragonfly mission to Titan to assess its habitability, with a launch currently slotted for 2028.
