Titan’s surface chemical composition: what we learnt after 13 years of Cassini exploration

The Cassini spacecraft spent 13 years in the Saturnian system and performed observations of Titan through 127 flybys, along with the in situ observations of the surface by Huygens. This led to the detailed investigation of Titan’s surface composition at both local and global scale. However, due to the complexity of Titan’s atmosphere and surface, the surface composition is only partially unveiled and is still considered to be one of Titan’s largest mysteries. Titan is resembling Earth like no other body in our solar system even though its mean surface temperature in -180 ºC (~93 K), and instead of silicate rocks like on Earth, water ice is abundant in the crust. Sedimentary deposits in the form of hydrocarbon grains cover the top layer of the surface, while liquid hydrocarbons are found in the polar lakes. Titan’s active geology with its resurfacing processes creates a surficial topography where exposed materials from the underlying ‘old’ crust along with new atmospheric sediments are present. After Cassini and Huygens with their several instruments investigated Titan for more than a decade one of the prevailing questions that still remains unanswered is whether and where water ice is exposed on the surface. Additionally, advanced knowledge with regards to the mixtures and the materials that create and cover the surface is yet to be gained from future missions and ground/space telescopes that would carry advanced technology. Here, we present an overview of what we have learnt so far about the composition as well as its correlation and constraints with regards to Titan’s astrobiology.