NASA’s Cassini spacecraft paused during its final close flyby of Enceladus to focus on the icy moon’s craggy, dimly lit limb, with the planet Saturn beyond. Layers can be seen in the high hazes of Saturn’s upper atmosphere, in the gradient that separates the planet from space. North on Enceladus is up and rotated 27 degrees to the left. The image was taken with the Cassini spacecraft narrow-angle camera on 19 December 2015, using a spectral filter, which preferentially admits wavelengths of near-infrared light. The view was acquired at a distance of approximately 15,000 miles (24,000 kilometres) from Enceladus. Image scale is 479 feet (146 metres) per pixel. Image credit: NASA/JPL-Caltech/Space Science Institute.NASA’s Cassini spacecraft has begun transmitting data and images from the mission’s final close flyby of Saturn’s active moon Enceladus. Cassini passed Enceladus at a distance of 3,106 miles (4,999 kilometres) on Saturday, 19 December at 5:49pm GMT (12:49pm EST).
“This final Enceladus flyby elicits feelings of both sadness and triumph,” said Earl Maize, Cassini project manager at JPL. “While we’re sad to have the close flybys behind us, we’ve placed the capstone on an incredible decade of investigating one of the most intriguing bodies in the solar system.”During its final close flyby of Saturn’s moon Enceladus, NASA’s Cassini spacecraft captured this view featuring the nearly parallel furrows and ridges of the feature named Samarkand Sulci. This view is centered on terrain at 13 degrees north latitude, 336 degrees west longitude. The image was taken with the Cassini spacecraft narrow-angle camera on 19 December 2015, using a spectral filter, which preferentially admits wavelengths of near-ultraviolet light. The view was acquired at a distance of approximately 8,000 miles (12,000 kilometres) from Enceladus. Image scale is 243 feet (74 metres) per pixel. Image credit: NASA/JPL-Caltech/Space Science Institute.Cassini will continue to monitor activity on Enceladus from a distance, through the end of its mission in September 2017. Future encounters will be much farther away — at closest, more than four times farther than this latest encounter.
This was the 22nd Enceladus encounter of Cassini’s mission. The spacecraft’s discovery of geologic activity there, not long after arriving at Saturn, prompted changes to the mission’s flight plan to maximise the number and quality of flybys of the icy moon.NASA’s Cassini spacecraft peered out over the northern territory on Saturn’s moon Enceladus, capturing this view of two different terrain types. A region of older terrain covered in craters that have been modified by geological processes is seen at right, while at left is a province of relatively craterless, and presumably more youthful, wrinkled terrain. Cassini acquired the view during its final close flyby of Enceladus, on 19 December 2015. North on Enceladus is up and rotated 38 degrees to the left. The image was taken in polarised green light with the Cassini spacecraft narrow-angle camera. The view was acquired at a distance of approximately 21,000 miles (34,000 kilometres) from Enceladus. Image scale is 668 feet (204 metres) per pixel. Image credit: NASA/JPL-Caltech/Space Science Institute.“We bid a poignant goodbye to our close views of this amazing icy world,” said Linda Spilker, the mission’s project scientist at NASA’s Jet Propulsion Laboratory in Pasadena, California. “Cassini has made so many breathtaking discoveries about Enceladus, yet so much more remains to be done to answer that pivotal question, ‘Does this tiny ocean world harbour life?'”
After revealing Enceladus’ surprising geologic activity in 2005, Cassini made a series of discoveries about the material gushing from warm fractures near its south pole. Scientists announced strong evidence for a regional subsurface sea in 2014, revising their understanding in 2015 to confirm that the moon hosts a global ocean beneath its icy crust.
Like cosmic ballet dancers, the stars of the Pleiades cluster are spinning, but all at different speeds. By watching these stellar dancers, NASA’s Kepler space telescope has helped amass the most complete catalogue of rotation periods for stars in a cluster. This information can provide insight into where and how planets form around these stars, and how such stars evolve.
Similar in many ways, Saturn’s moons Tethys and Rhea (left and right, respectively) even share a discoverer: Giovanni Cassini, namesake of the NASA spacecraft that captured this view. Although somewhat different in size, Rhea (949 miles across) and Tethys (660 miles) are both composed largely of ices and are generally thought to be geologically inactive today.
Much of the action on Mars occurred during a period known as the Late Heavy Bombardment about 3.9 billion years ago. Large comets and asteroids raining down on the planet would have produced enough heat to melt subsurface ice, likely enhancing climate conditions enough to make Mars more conducive to life — at least for a time.
