Moons
Moons

This free course is available to start right now. Review the full course description and key learning outcomes and create an account and enrol if you want a free statement of participation.

Free course

Moons

1.3.14 Orbital resonances at Saturn?

In fact there are two examples of 2:1 orbital resonances among Saturn’s principal moons. Mimas (0.942 days) and Tethys (1.888 days) are in 2:1 resonance with each other (2.0, rounded from 1.9832) and Enceladus (1.370 days) and Dione (2.737 days) are also in 2:1 resonance with each other (2.0, rounded from 1.9978).

The orbital resonance between Enceladus and Dione probably accounts for the present-day activity on Enceladus.

Resonant orbits do not remain constant. Their eccentricity (and hence the amount of heating) can increase or decrease over millions of years, and moreover moons can drift in and out of resonant relationships. Curiously, Mimas shows no signs on its surface that it was ever subject to significant tidal heating, but both Tethys and Dione show features that can be attributed to tidal heating in the distant past.

Next week you’ll find out more about moons, including what they are made of, but before that there’s the first end-of-week quiz.

MOONS_1

Take your learning further

Making the decision to study can be a big step, which is why you'll want a trusted University. The Open University has over 40 years’ experience delivering flexible learning and 170,000 students are studying with us right now. Take a look at all Open University courses.

If you are new to university level study, find out more about the types of qualifications we offer, including our entry level Access courses and Certificates.

Not ready for University study then browse over 900 free courses on OpenLearn and sign up to our newsletter to hear about new free courses as they are released.

Every year, thousands of students decide to study with The Open University. With over 120 qualifications, we’ve got the right course for you.

Request an Open University prospectus