Impact craters reveal details of Titan’s dynamic weathering

Scientists used data from NASA’s Cassini mission to excavate impact craters on Titan’s surface, revealing more details than ever before about how craters evolve and how time drives changes to the surface of the gigantic moon of Saturn.

Like Earth, Titan has a thick atmosphere that acts as a protective shield against meteorites; meanwhile, erosion and other geological processes effectively clear the craters formed by meteorites that reach the surface. The result is much less impact and craters than on other moons. Even so, because the impacts stir up what’s underneath and expose it, Titan’s impact craters reveal a lot.

The new examination showed that they can be divided into two categories: those of the dune fields around Titan’s equator and those of the vast plains at mid-latitudes (between the equatorial zone and the poles). Their location and composition are related: the craters between the dunes at the equator are made up entirely of organic matter, while the craters in the mid-latitude plains are a mixture of organic matter, water ice and a small amount of ice similar to methane.

From there, scientists took the connections a step further and found that craters evolve differently, depending on where they are on Titan.

Some of the new findings reinforce what scientists knew about the craters – that the mixture of organic matter and water ice is created by the heat of the impact, and those surfaces are then washed away by the methane rain. But as the researchers discovered that the clean-up process took place in the mid-latitude plains, they found that it did not occur in the equatorial region; instead, these impact zones are quickly covered with a thin layer of sandy sediment.

This means that Titan’s atmosphere and weather don’t just shape Titan’s surface; they also drive a physical process that affects materials that remain exposed on the surface, the authors found.

“The most exciting part of our results is that we found evidence of Titan’s dynamic surface hidden in the craters, which allowed us to deduce one of the most comprehensive stories from the surface evolution scenario of Titan to date, ”said researcher Anezina Solomonidou. at ESA (European Space Agency) and lead author of the new study. “Our analysis offers more evidence that Titan remains a dynamic world today.”

Unveiling secrets

The new book, recently published in Astronomy and astrophysics, used data from visible and infrared instruments aboard the Cassini spacecraft, which operated between 2004 and 2017 and made more than 120 flyovers of the Mercury-sized moon.

“The locations and latitudes seem to reveal many secrets of Titan, showing us that the surface is actively connected to atmospheric processes and possibly internal processes,” Solomonidou said.

Scientists are eager to learn more about Titan’s potential for astrobiology, which is the study of the origins and evolution of life in the universe. Titan is an oceanic world, with a sea of ​​water and ammonia beneath its crust. And as scientists search for ways for organic matter to move from the surface to the ocean below, impact craters provide a unique window into the subsoil.

The new research also found that an impact site, called the Selk Crater, is completely covered in organic material and has not been affected by the process of rain that cleans the surface of the other craters. Selk is actually a target for NASA’s Dragonfly mission, which is slated to launch in 2027; the rotorcraft lander will study key astrobiological questions as it searches for biologically important chemistry similar to that of early Earth before life emerges.

NASA had its first close encounter with Titan about 40 years ago, on November 12, 1980, when the agency’s Voyager 1 spacecraft flew a distance of only 2,500 miles (4,000 kilometers). Voyager images showed a thick, opaque atmosphere, and the data revealed that liquid may be present on the surface (this was – in the form of liquid methane and ethane), and indicated that prebiotic chemical reactions could be possible on Titan.

Managed by NASA’s Jet Propulsion Laboratory in Southern California, Cassini was an orbiter who observed Saturn for more than 13 years before depleting its fuel supply. The mission plunged it into the planet’s atmosphere in September 2017, in part to protect the moons that have the potential to contain conditions for life.