After 13 years of planetary exploration, Cassini was programmed to crash into Saturn’s atmosphere

Although this article [attached] is not exactly on the topic of “gene-environment interactions,” the Cassini Project should boggle the mind of anyone interested in science, as well as astronomy or reading Sci-Fi books. In mid-September, after 13 years of solar system exploration, NASA’s Cassini spacecraft plunged into the upper reaches of Saturn’s atmosphere at 123,000 kilometers per hour and melted. Beaming back its last measurements to Mission Control at the Jet Propulsion Laboratory (JPL) in Pasadena, California, the orbiter had remained intact for 30 seconds longer than expected, during its fiery plunge into the atmoshere. Finally, at 4:55 a.m. local time, the radio signals stopped: Cassini’s aluminum and polymer skeleton had likely vaporized.

The spacecraft’s demise –– necessitated by diminishing fuel and a need to protect two of Saturn’s 62 moons from potential microbial contamination from Earth –– was bitter-sweet news to the researchers who had worked on the project for a decade or longer. Before the final six orbits, Cassini had orbited Saturn only outside of the rings; thus, the scientists could not distinguish between masses of the planet and the rings. But, once it began threading the gap, scientists could untangle the two measures, which should help resolve a debate about the age of the rings and be informative to scientists about development of our Solar System.

The rings appear to be “young”, i.e. perhaps 100 million years old, because the constant rain of micrometeroid pollution would have darkened anything older. Other scientists had believed the rings might be “ancient”, i.e. billions of years old, developing during the early, chaotic days of the Solar System when large planetoids would have been present to collide and provide grist for the rings. These primordial collisions would have created massive rings. But Cassini is now finding hints of a relatively low mass, suggesting the rings were probably created more recently by the destruction of a comet or small moon. As scientists sift through data from the radio science experiment, their estimates of how mass is distributed throughout the planet itself should also improve.

Other data from the final plunge into the atmosphere have already made clear that the interior and exterior layers of the planet Saturn rotate with significantly different speeds. A similar pattern is seen with the sun –– but not with Jupiter –– where deep and shallow layers rotate with little difference in rotation speeds.

Science 22 Sept 2o17; 357: 1219–1220 [just 2 pages]

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