Science & Technology

Landscape of Saturn’s largest moon ‘Earth-like’ but compositions different: Study

Titan, one of Saturn’s 82 orbiting moons, can be one of the most hospitable regions in solar system

By Rohini Krishnamurthy
Published: Wednesday 04 May 2022
Landscape of Saturn’s moon ‘Earth-like’ but compositions different: Study Photo: NASA / JPL-Caltech / Space Science Institute

Saturn’s moon Titan holds liquid lakes, rivers and fields of sand dunes, much like Earth. But the ingredients that make up the landscapes of the two worlds are different. A new study puts forth a theory to explain how these features form on the “alien” moon despite the differences.

For instance, Titan’s sand dunes — rounded piles of sand deposited by the wind — contain hydrocarbons, unlike sand on Earth, according to the study published in Geophysical Research Letters.

The hydrocarbon grains that make up Titan’s landscape are soft and brittle and are expected to break down into dust. Instead, they remain grain-sized, Mathieu Lapôtre, one of the report’s authors and assistant professor of geological sciences at Stanford’s School of Earth, Energy & Environmental Sciences, told Down To Earth.

“Why Titan’s dunes have been active for tens to hundreds of thousands of years thus remained an open question,” the expert added. 

Titan is one of the 82 moons orbiting Saturn. This icy world can be one of the most hospitable regions in our solar system, according to the United States National Aeronautical and Space Administration (NASA). 

Methane lakes and sand dunes dot this mysterious world, showed data from the US space agency’s Cassini spacecraft and European Space Agency’s Huygens.

In this study, Lapôtre and his colleagues proposed a hypothesis to identify the forces that might have created Titan’s landscape, which is thought to host dunes at the equator, rocks in the mid-latitude and labyrinth terrains — eroded plateau areas — in the higher latitudes.

The research team turned to sediments on Earth called ooids — rounded, sand-sized particles of calcium carbonate found in shallow tropical seas — to find answers.

Ooids form when calcium carbonate from the water attaches in layers around a grain, such as quartz, the report noted.

While ooids grow as the mineral solidifies from a solution, they also break down when grains are smashed into each other by waves and storms. This process ensures the size stays constant, the researchers highlighted.

Something similar can be playing out on Titan, too, the researchers speculated. The hydrocarbon sediments might break down during their transport through wind or methane rivers. They are likely to grow back as fragments combine to form sand-sized grains during rest.

The moon is dry around the equator while its poles are wet due to an abundance of methane lakes.

At the equator, sand transport occurs primarily by winds, indicating the presence of fine sand grains — an ingredient of sand dunes, the authors hypothesised. 

In the labyrinth terrains of the higher latitudes, rivers might be providing coarse grains thought to make up the landscape, the paper stated.

As for mid-latitudes, the frequency of sediment transport is likely lower than at low and high latitudes, scientists observed. This means sediment grains experience less breakdown and more sintering, where grains accumulate to become larger over time, probably forming "rocks" in the process, the Lapôtre said.

He added:

Sedimentary "rocks" (which on Titan can be made of complex organics and ices) offer a prime target to better understand past environmental conditions, and thus, the history of Titan's surface and atmosphere. 

NASA believes Titan can be potentially habitable. The moon’s atmosphere contains roughly 95 per cent nitrogen and 5 per cent methane. The air is so dense that humans will not need a pressure suit to walk on the surface, according to the space agency.

Its atmosphere is also thought to be conducive to the type of prebiotic chemistry [organic compounds] that may have given rise to life on Earth, according to Lapôtre.

Humans, however, cannot survive on Titan without an oxygen mask and the moon’s average temperature is minus 179 degrees Celsius, according to NASA.

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