lundi 21 décembre 2015

Cassini Completes Final Close Enceladus Flyby










NASA - Cassini International logo.

Dec. 21, 2015

Enceladus, Old and New

Enceladus dramatically displays the contrast between its older and newer terrain.

Newer surfaces (on the left in the image) will not have had time to accumulate craters. But as material sits exposed on the surface, impact scars build up, as in the more heavily cratered area on the top and right. Scientists can use this, along with estimates of how frequently impacts happen, to determine ages of surfaces of solid planets and of moons like Enceladus (313 miles or 504 kilometers across).

This view looks toward the anti-Saturn side of Enceladus. North on Enceladus is up and rotated 36 degrees to the right. The image was taken in green light with the Cassini spacecraft narrow-angle camera on Aug. 18, 2015.

The view was acquired at a distance of approximately 85,000 miles (137,000 kilometers) from Enceladus. Image scale is 2,680 feet (818 meters) per pixel.


Image above: 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. Image Credits: 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 kilometers) on Saturday, Dec. 19, at 9:49 a.m. PST (12:49 p.m. 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."

Cassini will continue to monitor activity on Enceladus from a distance, through the end of its mission in Sept. 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 maximize the number and quality of flybys of the icy moon.


Image above: 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. Image Credits: 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 harbor 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.

In addition to the processed images, unprocessed, or "raw," images appear on the Cassini mission website at: http://saturn.jpl.nasa.gov/mission/flybys/enceladus20151219/

Additional information and multimedia products for Cassini's final Enceladus flybys are available at: http://solarsystem.nasa.gov/finalflybys


Image above: 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 Dec. 19, 2015. Image Credits: NASA/JPL-Caltech/Space Science Institute.

The Cassini mission is a cooperative project of NASA, ESA (the European Space Agency) and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colorado.

For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov or http://www.nasa.gov/cassini . The Cassini imaging team homepage is at http://ciclops.org and ESA's website: http://www.esa.int/Our_Activities/Space_Science/Cassini-Huygens

Images (mentioned), Text, Credits: Credits: NASA/JPL-Caltech/Preston Dyches/Space Science Institute/Tony Greicius.

Best regards, Orbiter.ch

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