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Researcher shows how elliptical craters could shed light on age of Saturn’s moons

SwRI researcher shows how elliptical craters could shed light on the age of Saturn's moons

A unique pattern of elliptical craters along the equator of Saturn’s Tethys and Dione satellites indicates slow and shallow east-west orbital impacts and the possibility of planetocentric collision populations similar to others in the outer solar system. Credit: NASA/JPL/SSI/Lunar and Planetary Institute

A new SwRI study describes how unique populations of craters on two of Saturn’s moons could help indicate the age of the satellites and the conditions of their formation. Using data from NASA’s Cassini mission, SwRI postdoctoral researcher Dr. Sierra Ferguson elliptical craters on Saturn’s moons Tethys and Dione for this study, which was co-authored with SwRI lead scientist Dr. Alyssa Rhoden, chief scientist Dr. Michelle Kirchoff and principal analyst Dr. Julian Salmon.

“Our work aims to answer the broader question of how old these moons are. To answer this question, my colleagues and I mapped elliptical craters on the surface of these moons to determine their size, direction and location on the moon. determine,” Ferguson said.

Round craters are common and can be formed by a wide variety of impact conditions. Elliptical craters are rarer, however, and are created by slow and shallow impacts, making them especially useful in determining an object’s age, as shape and orientation also indicate the orbit of the impactor.

“By measuring the direction these craters are pointing, we can get a sense of what the impactors that created these craters looked like in a dynamic sense and from which direction they would have hit the surface,” she said.

At first, Ferguson didn’t expect a pattern between the directions of the elliptical craters, but she eventually noticed a trend along Dione’s equator, one of Saturn’s minor moons. There, elliptical craters were overwhelmingly oriented in an east/west pattern, while the directions were more random close to the moon’s poles.

“We initially interpreted this pattern as being representative of two different impactor populations creating these craters,” she said. “One group was responsible for creating the elliptical craters at the equator, while another, less concentrated population may be more representative of the regular background population of impactors around Saturn.”

Ferguson also mapped elliptical craters on Tethys, Saturn’s fifth largest moon, and found that a similar size-frequency distribution of craters is unusual for objects orbiting the Sun, but strangely matches estimates for the impactor population present. appears to be on Neptune’s moon, Triton. Because that population is thought to be planetocentric, or attracted to the massive gravity of the ice giant, Ferguson’s results point to the importance of considering planetocentric impactors when investigating the age of objects in the Saturn system.

“It was really amazing to see these patterns,” she said.

Ferguson believes the equatorial craters may have formed from independent disks of debris orbiting each moon or possibly a single disk affecting both moons.

“Using Triton as a guideline, Tethys could reasonably be billions of years old. This age estimate depends on how much material was available to influence the surface and when it was available,” Ferguson said. “Of course we need more data to be sure, but this research tells us a lot. It can give us an idea of ​​what the formation conditions of these moons were like. Was this a system that was completely chaotic with materials all over these satellites? either way, or was there a neat and orderly system?”

Ferguson hopes eventually to be able to compare her data from Saturn’s moons with that of Uranus, another ice giant. While the current data is inconclusive, one of the flagship missions recommended by the Planetary Science Decadal Survey, published in April, is a mission to Uranus and its moons.

“This is the first step towards a new perspective on the crater history of these moons and their origin and evolution,” Ferguson said.

The study is published in Earth and Planetary Science Letters


New Chronology of the Saturn System


More information:
Sierra N. Ferguson et al, A unique Saturnian impactor population of elliptical craters, Earth and Planetary Science Letters (2022). DOI: 10.116/j.epsl.2022.117652

Provided by Southwest Research Institute


Quote: Researcher shows how elliptical craters could shed light on the age of Saturn’s moons (2022, June 21), retrieved June 21, 2022 from https://phys.org/news/2022-06-elliptical-craters-age -saturn-moons.html

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