Cassini Flies over Enceladus

Today “Cassini is set to begin a series of scraping Enceladus flybys that will take place in 2008 and will take us flying within a mere 50 km (~ 30 miles) over the equatorial region of the moon, approaching from the north and then departing towards the south, with passage through the edges of the moon's famous south polar plume” said Catheryn Porco, Cassini Imaging Team Leader. At closest approach, the spacecraft will pass the moon at a speed of about 14 kilometers (9 miles) per second. “We will make several daring plunges over the surface of Enceladus and through its plume of vapor and icy particles,” said Porco. “These maneuvers will take us deep into the plume and allow many of Cassini's instrument teams to improve their measurements of the region's properties. The heat-sensing instrument will map the terrain's thermal emission over a wider area than before in search of additional hot spots, and the instrument capable of sniffing out the plume's composition will improve tenfold its measurements of the plume's molecular concentrations. All of us are eager to learn if we are correct in suspecting that organic-rich, liquid water reservoirs are truly the sources of the moon's dramatic geologic activity…We should come away, in particular, with a better measure than we've had up until now of the abundances of ammonia and some simple organic compounds, both of which are important to ascertaining the astrobiological potential of the source environment of the jets.”

The Voyagers showed that Enceladus is only 500 km in diameter and reflects almost 100% of the sunlight that strikes it. Voyager 1 found that Enceladus orbited in the densest part of Saturn's diffuse E ring, indicating a possible association between the two, while Voyager 2 revealed that despite the moon's small size, it had a wide range of terrains ranging from old, heavily cratered surfaces to young, tectonically deformed terrain, with some regions with surface ages as young as 100 million years old.

The Cassini spacecraft of the mid- to late 2000s acquired additional data on Enceladus, answering a number of the mysteries opened by the Voyager spacecraft and starting a few new ones. As a result of several close flybys of Enceladus in 2005, the probe discovered a water-rich plume venting from the moon's south polar region. This discovery, along with the presence of escaping internal heat and very few (if any) impact craters in the south polar region, shows that Enceladus is geologically active today. Moons in the extensive satellite systems of gas giants often become trapped in orbital resonances that lead to forced libration or orbital eccentricity; proximity to the planet can then lead to tidal heating of the satellite's interior, offering a possible explanation for the activity.

Enceladus is one of only three outer solar system bodies (along with Jupiter's moon Io and Neptune's moon Triton) where active eruptions have been observed. Analysis of the outgassing suggests that it originates from a body of sub-surface liquid water, which along with the unique chemistry found in the plume, has fueled speculations that Enceladus may be important in the study of astrobiology.The discovery of the plume has added further weight to the argument that material released from Enceladus is the source of the E-ring (Wikipedia).

Enceladus was named after the Titan Enceladus of Greek mythology. The name was chosen because Saturn, known in Greek mythology as Cronus, was the leader of the Titans.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Cassini-Huygens mission for NASA's Science Mission Directorate, Washington, D.C. The imaging team consists of scientists from the US, England, France, and Germany. The imaging operations center and team lead (Dr. C. Porco) are based at the Space Science Institute in Boulder, Colo.For more information about the Cassini-Huygens mission, visit http://saturn.jpl.nasa.gov and the Cassini imaging team home page, http://ciclops.org.

Nina Munteanu is an ecologist and internationally published author of novels, short stories and essays. She coaches writers and teaches writing at George Brown College and the University of Toronto. For more about Nina’s coaching & workshops visit www.ninamunteanu.me. Visit www.ninamunteanu.ca for more about her writing.