Scientists approach the mystery that Saturn's moon Titan has 'sand dunes that should not exist'

Saturn's sixth satellite,

Titan , is the only satellite in the solar system with an abundant atmosphere and the only celestial body with a stable liquid on its surface outside of Earth. A research team led by Stanford University planetary geologist Mathieu Lapôtre on the mystery of 'there is an Earth-like sand dune that shouldn't exist' in Titan, which has some similar characteristics to the Earth. Proposed a new hypothesis.

The Role of Seasonal Sediment Transport and Sintering in Shaping Titan's Landscapes: A Hypothesis --Lapôtre --2022 --Geophysical Research Letters --Wiley Online Library

Scientists model landscape formation on Titan | Stanford News

This Giant Moon of Saturn Has Yet Another Strange Similarity to Earth

Titan is a celestial body composed mainly of ice and rock, and has a rich atmosphere consisting of nitrogen, methane , and ethane . In addition, Titan has a methane cycle similar to the water cycle of the earth, and it has been confirmed that liquid methane rains and rivers and lakes consisting of methane and ethane exist on the surface, which is similar to the earth. It is known for the existence of meteorological phenomena.

There are dunes like the earth in such Titan, but the existence of these dunes was a big mystery for scientists. Titan does have similar characteristics to the Earth, but its components are different, just as the methane cycle exists instead of the water cycle. Similarly, the sand dunes on Earth are mainly deposits of inorganic silicates , but Titan's sand dunes are made up of particles of organic compounds that are more mechanically brittle than inorganic silicates.

'When the wind carries a particle, it collides with another particle or the surface of Titan, which tends to make the particle smaller over time,' Lapôtre said. Over time, the particles that make up Titan's dunes will wear out into smaller dust, eventually failing to maintain a dune-like aggregated structure that requires large, coarse particles.

However, the dunes near the equator of Titan are likely to have been maintained for tens of thousands to hundreds of thousands of years, so there is some mechanism to maintain particle size over the geological scale. Can be inferred that exists. “We didn't have a growth mechanism that could counteract the reduction in particle size due to wear and maintain a stable size over time,” says Lapôtre.


Kevin Gill

The research team devised a mechanism to explain this mystery, inspired by particles called ' ooids ' that are often found on the shallow tropical seabed such as around the Bahamas. Ooids are rounded particles with a diameter of 2 mm or less, and the nucleus composed of bioskeletal particles and quartz particles is covered with a layer such as calcium carbonate.

A characteristic of ooids is that the material that forms the outer layer of the nucleus is attached via chemical precipitation in the marine environment, and the particles become larger over time. By balancing the growth speed of these particles with the erosion speed of the particles due to being exposed to waves, the ooid maintains a stable particle size for a certain period of time.

According to the research team's modeling, the existence of organic particles in Titan can be explained by a process similar to that of ooids. The research team suggests that Titan may grow by sintering adjacent organic particles into a single mass, counteracting the size reduction due to wear. This mechanism of maintaining particle size is important not only for the dunes near the equator, but also for forming the terrain near the poles.

'We were able to solve the paradox of why Titan had dunes for so long, despite the very brittle materials,' Lapôtre said. 'Even though it's so far away and the materials are different.' It's very fascinating to think that there is another world that is so similar. '

by NASA's Marshall Space Flight Center

in Science, Posted by log1h_ik