Bengaluru: The first full, global geological map of Saturn’s largest moon Titan was revealed Monday, showing an elaborate geological features similar to that of Earth, as was expected, including large plains, lakes of liquid methane, mountains and valleys, craters and more.
The map, published by Nature Astronomy, also hinted at the potential for an increased probability of life on the planetary body.
The mapping was performed through radar and infrared measurements taken by Cassini mission from 2004 to 2017. This was because Titan is shrouded with thick clouds that obscure the surface in visible light.
Cassini was a highly ambitious and successful mission launched by the joint effort of NASA, the European Space Agency and the Italian Space Agency to study the planet Saturn and its system. The spacecraft was launched with two elements — the Cassini orbiter and the Huygens lander probe.
On Earth, there exists a water cycle — evaporation from water bodies that causes cloud formation, which then leads to rainfall, and flow of water into water bodies. On Titan, instead of water, hydrocarbons like methane and ethane go through the same process.
Titan is the only other object in the solar system where liquids can remain stable on the surface.
These hydrocarbons are in the form of gas on Earth, but are liquid on Titan due to the exceedingly cold temperatures there, which average around -180 °C. Methane and ethane rain down everywhere, throughout Titan, but rainfall is less around the equatorial region and higher in the poles, according to the new study.
“These hydrocarbons rain down on the surface, flow in streams and rivers, accumulate in lakes and seas, and evaporate into the atmosphere. It’s quite an astounding world,” the study said.
Also read: Saturn overtakes Jupiter with 82 moons — now has more than any other planet
Primary geological features
The map identifies six primary features on the surface of Titan, described by NASA as “plains (broad, relatively flat regions), labyrinth (tectonically disrupted regions often containing fluvial channels), hummocky (hilly, with some mountains), dunes (mostly linear dunes, produced by winds in Titan’s atmosphere), craters (formed by impacts) and lakes (regions now or previously filled with liquid methane or ethane)”.
Among the most prominent surface features, plains cover 65 per cent of the surface and dunes of frozen hydrocarbons, which create sand-like structures, cover 17 per cent of the surface. Dunes are more frequently found near the equatorial region. Hills and mountains made up of water ice constitute 14 per cent.
Most lakes on Titan are near its North Pole, leading scientists to think that because of Saturn’s highly elliptical orbit around Sun, the summer in the northern hemisphere is longer.
Understanding the surface features also enables us to understand Titan’s formation and evolution, adding more clues into our ever-expanding knowledge of the formation of the solar system.
Contender for life
Titan has been a strong contender for habitability in the solar system, primarily due to the abundance of hydrocarbons, which are organic materials made of carbon and essential components for life to form, given the right set of conditions.
Some of the favorable conditions can be found in liquid water, underneath icy crusts on moons in the solar system like Titan, on another of Saturn’s icy moons called Enceladus or on Jupiter’s Europa.
Some studies, including observations from Cassini, have suggested that liquid water could exist beneath the crust in an isolated layer, while others have proposed that a mixture of ammonia and water (as on Titan) could be an alternative.
Whether there is life on Titan or not is an open question that the new study does not answer.
NASA’s Dragonfly mission
Titan is the only known moon in the solar system that hosts a fully-formed atmosphere that can contain more than just trace gases. Just like liquids on the surface, Titan’s clouds are rich with hydrocarbons. Experiments have shown that upon passing energy through a simulated Titan environment, building blocks of DNA and RNA have been produced.
Titan was also visited by Cassini’s companion craft, the Huygens probe, which landed on its surface in 2005. The spacecraft, named after the discoverer of Titan, Christiaan Huygens, transmitted data for 90 minutes. It is the only landing to have taken place in the outer solar system and the farthest landing any spacecraft has performed from Earth.
NASA is also planning to send another mission to Titan, called Dragonfly. This mission will be a mobile rotorcraft, which would function like a helicopter in Titan’s hazy skies. It is planned to be launched in 2026.
Also read: NASA mission Dragonfly will scout for signs of life on largest Saturn moon Titan