Heat radiating from the entire length of 150 kilometer (95 mile)-long fractures is seen in this best-yet heat map of the active south polar region of Saturn's ice moon Enceladus.

NASA's Saturn-bound Cassini spacecraft examined and sampled a surprising organic brew erupting in geyser-like phenomenon from Saturn's moon Enceladus during a close flyby on 12 March 2008. Scientists are amazed by the geologic activity and chemical composition of this small moon.

New heat maps of Enceladus’ surface show higher temperatures than previously measured in the moon’s south polar region, with hot tracks running along giant fissures. Further, scientists say the organics "taste and smell" like some of those found in comets. The jets themselves harmlessly bombarded Cassini, exerting measurable torque on the spacecraft, and yielding an indirect measure of the plume density.

"A completely unexpected surprise is that the chemistry of Enceladus, what's coming out from inside, resembles that of a comet," said Hunter Waite, Principal Investigator of the Cassini Ion and Neutral Mass Spectrometer (Southwest Research Institute). "To have primordial material coming out from inside a Saturn moon raises many questions on the formation of the Saturn system."

"Enceladus is by no means a comet. Comets have tails and orbit the Sun, and Enceladus' activity is powered by internal heat while comet activity is powered by sunlight. Enceladus' brew is like carbonated water with an essence of natural gas," said Waite.

The Ion and Neutral Mass Spectrometer recorded a much higher density of volatile gases, water vapor, carbon dioxide and carbon monoxide, as well as organic materials, some 20 times denser than expected. This drastic increase in density was remarkable when the spacecraft flew over the area of Enceladus’ plumes.

New high-resolution heat maps of the south pole of Enceladus by Cassini's Composite Infrared Spectrometer show that the “tiger stripes”, giant fissures that are the source of the geysers, are warm along almost their entire lengths, and reveal other warm fissures nearby.
These more precise new measurements reveal temperatures of at least minus 93 degrees Celsius. That is 17 degrees Celsius warmer than previously observed and 93 degrees Celsius warmer than other regions of Enceladus. The warmest regions along the tiger stripes correspond to two of the jet locations visible in Cassini images.

"These spectacular new data will really help us understand what powers the geysers. The surprisingly high temperatures make it more likely that there's liquid water not far below the surface," said John Spencer, Cassini scientist from the Composite Infrared Spectrometer team at the Southwest Research Institute.

Previous ultraviolet observations showed four jet sources, matching the sites of the plumes visible in previous images. This indicates that gas in the plume blasts off the surface into space, blending to form the larger plume.

Images acquired through previous observations show individual jets and mark locations from which they emanate. New images show how hot spot fractures are related to other surface markings. In future imaging observations, scientists hope to detect individual plume sources and investigate differences among fractures.

"Enceladus has got warmth, water and organic chemicals, some of the essential building blocks needed for life," said Dennis Matson, Cassini project scientist at NASA's Jet Propulsion Laboratory (JPL). "We have quite a recipe for life on our hands, but we have yet to find the final ingredient, liquid water, but Enceladus is only whetting our appetites for more."

At closest approach, Cassini was only 50 km from Enceladus. When it flew through the plumes it was about 190 km from the moon's surface. Cassini's next flyby of Enceladus is in August 2008.

Further Reading

NASA’s Cassini Websites
http://www.nasa.gov/cassini
http://saturn.jpl.nasa.gov/.

Aymen Mohamed Ibrahem
Senior Astronomy Specialist