Cassini Finds an Atmosphere on Saturn's Moon Enceladus

Mar 16, 2005
This false-color, close-up look at Saturn's moon Enceladus yields new insight into the different processes that have shaped the

The Cassini spacecraft's two close flybys of Saturn's icy moon Enceladus have revealed that the moon has a significant atmosphere. Scientists, using Cassini's magnetometer instrument for their studies, say the source may be volcanism, geysers, or gases escaping from the surface or the interior.
When Cassini had its first encounter with Enceladus on Feb. 17 at an altitude of 1,167 kilometers (725 miles), the magnetometer instrument saw a striking signature in the magnetic field. On March 9, Cassini approached to within 500 kilometers (310 miles) of Enceladus' surface and obtained additional evidence.

Image: This false-color, close-up look at Saturn's moon Enceladus yields new insight into the different processes that have shaped the moon's icy surface.

The observations showed a bending of the magnetic field, with the magnetospheric plasma being slowed and deflected by the moon. In addition, magnetic field oscillations were observed. These are caused when electrically charged (or ionized) molecules interact with the magnetic field by spiraling around the field line. This interaction creates characteristic oscillations in the magnetic field at frequencies that can be used to identify the molecule. The observations from the Enceladus flybys are believed to be due to ionized water vapor.

"These new results from Cassini may be the first evidence of gases originating either from the surface or possibly from the interior of Enceladus," said Dr. Michele Dougherty, principal investigator for the Cassini magnetometer and professor at Imperial College in London. In 1981, NASA's Voyager spacecraft flew by Enceladus at a distance of 90,000 kilometers (56,000 miles) without detecting an atmosphere. It's possible detection was beyond Voyager's capabilities, or something may have changed since that flyby.

This is the first time since Cassini arrived in orbit around Saturn last summer that an atmosphere has been detected around a moon of Saturn, other than its largest moon, Titan. Enceladus is a relatively small moon. The amount of gravity it exerts is not enough to hold an atmosphere very long. Therefore, at Enceladus, a strong continuous source is required to maintain the atmosphere.

The need for such a strong source leads scientists to consider eruptions, such as volcanoes and geysers. If such eruptions are present, Enceladus would join two other such active moons, Io at Jupiter and Triton at Neptune. "Enceladus could be Saturn's more benign counterpart to Jupiter's dramatic Io," said Dr. Fritz Neubauer, co-investigator for the Cassini magnetometer, and a professor at the University of Cologne in Germany.

Since the Voyager flyby, scientists have suspected that this moon is geologically active and is the source of Saturn's icy E ring. Enceladus is the most reflective object in the solar system, reflecting about 90 percent of the sunlight that hits it. If Enceladus does have ice volcanoes, the high reflectivity of the moon's surface might result from continuous deposition of icy particles originating from the volcanoes.

Enceladus' diameter is about 500 kilometers (310 miles), which would fit in the state of Arizona. Yet despite its small size, Enceladus exhibits one of the most interesting surfaces of all the icy satellites.

Source: NASA

Explore further: N. America treated to partial solar eclipse Thurs.

add to favorites email to friend print save as pdf

Related Stories

Ten years of Cassini

Sep 09, 2014

Ten years ago, the Cassini-Huygens mission entered the Saturnian System and in January 2005, the Huygens probe landed softly on the surface of Saturn's largest moon, Titan. These historic events, which revolutionized ...

How Titan's haze help us understand life's origins

Aug 25, 2014

Where did life on Earth come from? There are several theories as to what might have happened. Maybe comets came bearing organic material, or life was transported from another planet such as Mars, or something ...

Cassini flyby focuses on Saturn's moon Enceladus

Nov 08, 2011

(PhysOrg.com) -- Saturn's moon Enceladus shows its icy face and famous plumes in raw, unprocessed images captured by NASA's Cassini spacecraft during its successful flyby on Nov. 6, 2011.

Recommended for you

Big black holes can block new stars

3 hours ago

Massive black holes spewing out radio-frequency-emitting particles at near-light speed can block formation of new stars in aging galaxies, a study has found.

MAVEN studies passing comet and its effects

4 hours ago

NASA's newest orbiter at Mars, MAVEN, took precautions to avoid harm from a dust-spewing comet that flew near Mars today and is studying the flyby's effects on the Red Planet's atmosphere.

POLARBEAR seeks cosmic answers in microwave polarization

4 hours ago

An international team of physicists has measured a subtle characteristic in the polarization of the cosmic microwave background radiation that will allow them to map the large-scale structure of the universe, ...

User comments : 0