How The Seasons Shaped An Earth-Like Moon Near Jupiter

Sediments laden with the building blocks of life shaped the Earth-like landscapes of Titan, a moon at Saturn filled with prebiotic chemistry, a new study suggests.

A new study examines how delicate organic compounds managed to survive eons of erosion and recycling to build up a sandy landscape much like what we see on our own planet and other rocky worlds like it, especially Mars.

While researchers have found no firm evidence for life on Titan, its enigmatic chemistry and its dense atmosphere (of nitrogen) appear to be reminiscent of how weather works on our own planet. The new study builds on past research by showing how grains of sand were able to persist, organic compounds intact, over geologic eons.

“The research team found an answer by looking at sediments on Earth called ooids, which are small, spherical grains most often found in shallow tropical seas, such as around the Bahamas,” Stanford University said in a statement. “Ooids form when calcium carbonate is pulled from the water column and attaches in layers around a grain, such as quartz.”

Ooids grow through chemical precipitation even as they are worn away by erosion, due to grains crashing against each other during high winds or stormy conditions. “These two competing mechanisms balance each other out through time to form a constant grain size – a process the researchers suggest could also be happening on Titan,” Stanford stated. Sintering, which happens as neighboring grains stick together into a single piece, could also counteract any abrasion during wind-borne erosion.

Researchers used modeling of the atmosphere, along with data, from the Cassini mission that ran at Saturn and its moons between 2004 and 2017. This information showed that equatorial winds are common, but there is likely less sintering there that allows fine-grained dunes to form. Sintering, however, would be dominant in the latitudes straddling the equator, creating the bedrock underlying Titan’s plains.

“Labyrinth” terrains close to the poles likely formed like karsts in limestone on Earth, except using dissolved organic sandstones on Titan. The poles are also associated with more liquid flow and rainstorms, creating river-borne transport for the sediments that would create coarse sand grains. These sandstones would eventually create the labyrinth terrains.

“We’re showing that on Titan – just like on Earth and what used to be the case on Mars – we have an active sedimentary cycle that can explain the latitudinal distribution of landscapes through episodic abrasion and sintering driven by Titan’s seasons,” lead author Mathieu Lapôtre, a Stanford University geologist, said in the same statement. “It’s pretty fascinating to think about how there’s this alternative world so far out there, where things are so different, yet so similar.”

A study based on the research was published in Geophysical Research Letters.

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