Three Moons and a Dance of Gravity



Saturn's moons

Image courtesy NASA/ESA/JPL

Three Moons and a
Dance of Gravity

| published February 22, 2016 |

By Keith H. Roberts, Thursday Review contributor


In this recent photograph taken in visible light from the Cassini spacecraft near Saturn, three of Saturn’s moons are visible in an unusual grouping. The image shows Tethys (above the plane of the rings), Enceladus (closer to the center), and the smaller Mimas.

This image—captured at a distance of about 837,000 miles from Enceladus—was taken from an angle of 0.4 degrees above the ring plane, and slightly below the orbit of Tethys. The photo shows the apparent eerie smoothness of the rings, as well as the deep scars and pockmarks of many of Saturn’s moon, which have met with frequent and violent encounters with objects such as asteroids and meteors.

The image is also a powerful reminder of the elegant and complex ballet of gravity within our solar system, for Saturn has more than 50 objects it calls its moons, ranging in size from the largest (Titan, at 2,201 miles in diameter, it is so large it has its own atmosphere) to small irregularly-shaped objects made of dense rock and ice, including Mimas, pictured here. Mimas is a favorite of astronomers—professional and amateur—for its enormous central impact crater, which, seen from a distance, gives Mimas a striking similarity to the infamous “Death Star” of the early Star Wars trilogies.

The Cassini mission is a collaborative effort of NASA, the European Space Agency (ESA), and the Italian Space Agency (ISA). The cameras were developed, designed and installed by a team at the Jet Propulsion Laboratory in Pasadena, California.

Related Thursday Review articles:

Half Moon, Or Half Enceladus; Thursday Review staff; Thursday Review; January 25, 2016.

Earthrise, 2016: Welcome to the New Year; Thursday Review staff; Thursday Review; January 7, 2016.