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Saturn’s rings were formed when dinosaurs roamed Earth

17 Jan 2019, 19:00 UTC
Saturn’s rings were formed when dinosaurs roamed Earth
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Saturn’s rings are just 100 million years old and formed when dinosaurs roamed Earth. This is much younger than Saturn, which formed about 4.5 billion years ago. Their age was determined by studying doppler-shifted radio signals from the doomed Cassini spacecraft. The signals were transmitted during the mission’s final orbits around Saturn and have also revealed startling details about the unseen interior of the planet.

Cassini used its Radio Science Subsystem to measure Saturn’s gravitational field. Saturn’s gravity tugged on the spacecraft, so any radio signals it beamed back to Earth exhibit a tiny Doppler shift, just 10 cm/s, as a consequence.
Radio transmissions made earlier in the mission, from outside of Saturn’s rings, gave a measurement of the gravitational field of both the planet and its rings. Cassini’s “grand finale” in 2017, however, saw the spacecraft’s orbit move inwards, between the planet and the rings, before the spacecraft entered Saturn’s atmosphere and was destroyed on 15 September 2017. By travelling between the planet and the rings, the radio signals were Doppler-shifted by gravity acting in different directions – the planet alone on one side, and the rings on the other. By disentangling these signals, it was possible to obtain ...

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