Cassini measures geisers of Saturn’s moon Enceladus

Cassini data obtained during a close flyby of the Saturn moon Enceladus support an observation that large amounts of water are spewing into space from the tiny moon’s surface. This water originates near south polar “hot spots” on the moon, possible locations for the development of primitive life in the solar system.

Announced by the Cassini Imaging Science Team in today’s issue of Science, the theory is bolstered by measurements from the Cassini Plasma Spectrometer (CAPS), as reported in the same issue by a team led by Robert Tokar of Los Alamos National Laboratory. CAPS was partly designed and built at Los Alamos.

“During the July 14 close flyby we began getting signatures, far from Enceladus, of water ejection. From the deflections we could measure of the ionized gas in the magnetosphere, it was erupting at 100 kg per second (220 lbs per second), and the data are consistent with measurements from the spacecraft’s other instruments. It is actual H20 molecules,” said Tokar.

Enceladus is a small moon, but highly reflective due to the fresh layer of snow and ice on its surface. Tokar suggests that the icy geisers at the south pole, erupting from a series of cracks, are pumping a continuous flow of water particles into the area above the moon. Much of the material falls back to the surface as snow.

In addition to constantly refreshing the snowy moon’s surface, the geisers also appear to be supplying oxygen atoms to the planet’s E ring. Like an icy version of a steam engine, the little moon is chugging around its parent planet, leaving a floating trail visible to the spacecraft’s cameras and strong telescopes.

“Our paper, with 12 coauthors from US and Europe, looks at the plasma of hydrogen, water and electrons in the ionized gas of the magnetosphere. The magnetosphere itself deflects in the vicinity of Enceladus, and we measure the plasma and that deflection. That is how we were able to determine the amount of water being ejected,” said Tokar.