Cassini Still Going Strong

Saturn’s third-largest moon Dione can be seen through the haze of Titan in this view from NASA’s Cassini spacecraft. The rings, viewed nearly edge-on, appear as a horizontal line through the image. The rings cast shadows on Saturn, which appear as dark lines at the bottom of the image. Credit: NASA/JPL-Caltech/Space Science Institute

NASA’s longstanding Cassini mission to Saturn continues to provide scientists with exciting new insights on moons Titan and Enceladus as well as the planet’s striking rings, Planetary Science Institute Senior Scientist Amanda R. Hendrix reported at a conference.

“Cassini, our emissary in the Saturn system since 2004, and the only spacecraft in orbit in the outer solar system, is still going strong,” said Hendrix, who spoke today on “The Organic Lakes of Titan and Other Moons of Saturn” at the American Association for the Advancement of Science annual meeting in Boston.

“Cassini’s longevity allows the study of seasonal variations, along with temporal variations on a variety of scales — and its suite of 12 instruments is making complementary measurements, providing insight into different aspects of various scientific discoveries,” Hendrix, an investigator on the Cassini mission, said.

These areas of study include Titan’s lakes: composition, depth and seasonal variability; Titan’s weather patterns; the interior structure of Titan; Enceladus’ startling plume activity; surprises on the other moons, such as Iapetus, Dione and Mimas; and Saturn’s bizarre collection of small moons.

Cassini will remain in orbit around Saturn until September 2017. The spacecraft began increasing its orbital inclination again last year, allowing for prime viewing of the magnificent rings, as well as the high latitudes of the planet and Titan.

A Cassini image of vaporous, icy jets emerging from fissures on Enceladus. Credit: NASA/JPL/SSI; Mosaic: Emily Lakdawalla

The first glimpses of Titan’s surface were provided by the Huygens probe, launched as part of the Cassini-Huygens mission. The probe was released in late 2004 and made its way through the hazy atmosphere of Titan to the surface in January 2005. Images of Titan’s surface — including its amazing lakes, dunes and river channels — continue to be returned by Cassini’s radar instrument, along with the imaging camera and the infrared mapping spectrometer. The remaining instruments in Cassini’s payload study the atmosphere, and its seasonal variations, while the radio science antenna makes measurements of Titan’s interior structure and its subsurface ocean.

“When Cassini arrived at Saturn, it was winter in the northern hemisphere of Titan, roughly like January on Earth. Now it’s the equivalent of May on Titan, so spring in the north. And we’re seeing significant variations on Titan that are the result of this seasonal transition,” Hendrix said. Such changes include the rain at low latitudes causing surface changes, and atmospheric variations such as haze layer changes and polar vortex evolution. “By continuing to observe and study Titan, we can put together the pieces of the puzzle of its methane-based hydrological cycle.”

Enceladus and its active south polar plume also continue to amaze, as it steadily ejects vapor and fine ice particles into the Saturn system. In Hendrix’s talk, she reviewed a summary of results from Enceladus and some of Saturn’s other intriguing moons.