One of Saturn's moons is spraying icy particles into space from the area around its south pole, a sure sign of geologic activity, NASA reported Tuesday.
Recent images captured by the Cassini spacecraft reveal what looks at first like the narrow crescent shape of a solar eclipse, with plumes of particles being ejected from the Saturn moon Enceladus.
"For planetary explorers like us, there is little that can compare to the sighting of activity on another solar system body," Carolyn Porco, Cassini imaging team leader at the Space Science Institute, said in a statement. "This has been a heart-stopper, and surely one of our most thrilling results."
The Cassini images of Enceladus show multiple jets emanating from the moon's south polar region. Scientists suspect these jets arise from warm fractures, known as tiger stripes.
A faint extended plume stretches 300 miles (483 kilometers) above the surface of Enceladus, which is only 300 miles (483 kilometers) wide.
Andrew Ingersoll, an imaging team member from the California Institute of Technology in Pasadena, said he believes the images show ice particles in jets of water vapor emanating from pressurized vents.
To fling these particles aloft, the vapor must have a certain density, and Ingersoll said this implies "surprisingly warm temperatures for a cold body like Enceladus."
NASA and Cassini's imaging team featured other images of Saturn's moons as well on Tuesday, in conjunction with this week's American Geophysical Union's autumn meeting in San Francisco. Among the highlights were "movies" of Cassini's close encounters with Hyperion and Iapetus; closeup views of Rhea; and enhanced-color imagery of Rhea, Dione and Hyperion.
The Cassini-Huygens mission is a project of NASA and the European and Italian space agencies.