While NASA's Cassini plunged near Saturn in its final year, the probe provided complex details about the operation of Saturn's complex rings, a new analysis reveals.
Although the mission ended in 2017, science continues to flow from the data collected. In a new article published on June 13 in Science, we describe the results obtained by four Cassini instruments taking into account the nearest observations of the main rings.
The results include fine details of features sculpted by masses embedded in the rings. Textures and patterns, from mass to straw, emerge from the images, asking questions about the interactions that shaped them. New maps reveal how colors, chemistry and temperature change from one ring to the next.
As a planet under construction inside a disk of protoplanetary material, tiny moons embedded in the rings of Saturn (named A to G, in the order of their discovery) interact with the particles who surround them. In this way, the paper provides further evidence that the rings are a window onto the astrophysical disk processes that shape our solar system.
The observations also allow scientists to better understand the complex system of Saturn. The scientists conclude that, on the outer edge of the main rings, a series of similar streaks generated by an impact in the F ring have the same length and the same orientation, which shows that they were probably caused by a group of impacts that all hit the ring at the same time. time. This shows that the ring is formed by streams of material that revolve around Saturn itself rather than, for example, by cometary debris (moving around the Sun) that breaks in the rings.
"These new details on how moons carve rings in different ways open a window to the formation of the solar system, where records also evolve under the influence of masses embedded in them," said Matt Tiscareno , principal author and scientist at Cassini, of SETI. Institute in Mountain View, California.
At the same time, new puzzles appeared and old mysteries widened with the latest research. Close-up ring images have highlighted three distinct textures – grouped, smooth and striated – and have clearly shown that these textures appear in sharp-edged belts. But why? In many places, belts are not connected to ringing features that scientists have identified.
"This tells us that the appearance of the rings is not only a function of the amount of material available," Tiscareno said. "There must be something different about particle characteristics, perhaps affecting what happens when two ring particles collide and bounce, and we do not know what it is."
The analyzed data was collected during the Ring Grazing Orbits (from December 2016 to April 2017) and the grand finale (from April to September 2017), when Cassini flew over the top of Saturn's clouds. While the satellite was running out of fuel, the mission team deliberately plunged it into the planet's atmosphere in September 2017.
The Cassini Visible and Infrared Mapping Spectrometer (VIMS) revealed another mystery. The spectrometer, which visualized the rings in visible light and in the near infrared, identified unusually weak bands of water ice in the outermost part of the ring A. It was a surprise, because we know that the region is very reflective, which is generally the sign of a less contaminated ice and therefore bands of ice water stronger.
The new spectral map also highlights the composition of the rings. And while scientists already knew that water ice was the main component, the spectral map excluded detectable ice from ammonia and ice from methane as ingredients. But he does not see organic compounds either – a surprise, given the organic matter that Cassini discovered that flowed from the D ring into Saturn 's atmosphere.
"If organic matter was present in large quantities – at least in the main A, B and C networks – we would see it," said Phil Nicholson, Cassini VIMS scientist at Cornell University in Ithaca, New York. "I am not yet convinced that they are a major component of the main rings."
The research marks the beginning of the next era of Cassini science, said Jeff Cuzzi of NASA's Ames Research Center, who has been studying Saturn's rings since the 1970s and is the interdisciplinary scientist of the Cassini mission rings.
"We're seeing a lot more and getting closer, and we're getting new, more interesting puzzles," said Cuzzi. "We are moving to the next phase, which involves building new detailed models of the evolution of the rings – including the new revelation from Cassini's data that the rings are much younger than Saturn. "
The new observations give scientists an even more intimate view of the rings than before and each review reveals new complexities, said Linda Spilker, Cassini project scientist, based at NASA's Jet Propulsion Laboratory in Pasadena, California.
"It's as if we're still increasing the power over what we could see in the rings." Everyone now has a clearer view of what's going on, "Spilker said. "The obtaining of this additional resolution has answered many questions, but there are still so many tempting ones."
The Cassini-Huygens mission is a collaborative project of NASA, ESA (European Space Agency) and the Italian Space Agency. JPL, a division of Caltech in Pasadena, manages the mission of NASA's Scientific Missions Directorate in Washington. JPL has designed, developed and assembled the Cassini orbiter. The radio antenna was built by JPL and the Italian Space Agency, in collaboration with members of the team from the United States and several European countries.
More information on Cassini can be found here: https://solarsystem.nasa.gov/cassini