Insight Web Extra June 2009
—Scientists working on NASA’s nuclear-powered Cassini mission have detected sodium salts in ice grains of Saturn's outermost ring. Detecting salty ice indicates that Saturn's moon Enceladus, which primarily replenishes the ring with material from discharging jets, could harbor a reservoir of liquid water—perhaps an ocean—beneath its surface.
Cassini discovered the water-ice jets in 2005 on Enceladus. These jets expel tiny ice grains and vapor, some of which escape the moon’s gravity and form Saturn’s outermost ring. Cassini’s cosmic dust analyzer has examined the composition of those grains and found salt within them.
“We believe that the salty minerals deep inside Enceladus washed out from rock at the bottom of a liquid layer,” said Frank Postberg, Cassini scientist for the cosmic dust analyzer at the Max Planck Institute for Nuclear Physics in Heidelberg, Germany. Postberg is lead author of a study that appears in the June 25 issue of the journal Nature.
Scientists on Cassini's cosmic dust detector team conclude that liquid water must be present because it is the only way to dissolve the significant amounts of minerals that would account for the levels of salt detected.
The team will get their next opportunity to gather data on Enceladus during two flybys in November.
The Cassini-Huygens mission, launched in 1997, is a cooperative project of NASA, the European Space Agency and the Italian Space Agency.
Electrical power for Cassini, and other deep-space probes, is provided by radioisotope thermoelectric generators. RTGs are essential for deep-space missions, where the sun is too distant for solar-powered generators. RTGs use long-lived plutonium-238 to generate heat, which is converted directly to electricity for the spacecraft’s computers, transmitters and other systems.
If you’d like to keep track of the exciting discoveries being made by the ongoing Cassini and New Horizons missions, visit NASA's current mission site
NEI also has a web page
on how radioactive isotopes are used to power these missions. Cassini imaging scientists used views like this one to help them identify the source locations for individual jets spurting ice particles, water vapor and trace organic compounds from the surface of Saturn's moon Enceladus. [Image credit: NASA/JPL/Space Science Institute]
—Read more articles in Nuclear Energy Insight and Insight Web Extra.