mardi 21 mars 2017
A Resolution & Pan Revealed
NASA & ESA - Cassini-Huygens Mission to Saturn & Titan patch.
March 21, 2017
NASA's & ESA's Cassini spacecraft zoomed in on Saturn's A ring, revealing narrow, detailed structures that get even finer as the cameras' resolution increases. Even at this level of detail, it is still not fine enough to resolve the individual particles that make up the ring.
High-resolution images like this help scientists map the fine structure of Saturn's rings. Features less than a half a mile (one kilometer) in size are resolvable here. But the particles in the A ring typically range in size from several meters across down to centimeters, making them still far too small to see individually here.
This view looks toward the sunlit side of the rings from about 38 degrees above the ring plane. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on Jan. 9, 2017.
The view was obtained at a distance of approximately 70,000 miles (113,000 kilometers) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 11 degrees. Image scale is 2,300 feet (690 meters) per pixel.
These two images from NASA's & ESA's Cassini spacecraft show how the spacecraft's perspective changed as it passed within 15,300 miles (24,600 kilometers) of Saturn's moon Pan on March 7, 2017. This was Cassini's closest-ever encounter with Pan, improving the level of detail seen on the little moon by a factor of eight over previous observations.
The views show the northern and southern hemispheres of Pan, at left and right, respectively. Both views look toward Pan's trailing side, which is the side opposite the moon's direction of motion as it orbits Saturn.
Cassini imaging scientists think that Pan formed within Saturn's rings, with ring material accreting onto it and forming the rounded shape of its central mass, when the outer part of the ring system was quite young and the ring system was vertically thicker. Thus, Pan probably has a core of icy material that is denser than the softer mantle around it.
The distinctive, thin ridge around Pan's equator is thought to have come after the moon formed and had cleared the gap in the rings in which it resides today. At that point the ring was as thin as it is today, yet there was still ring material accreting onto Pan. However, at the tail end of the process, that material was raining down on the moon solely in (or close to) its equatorial region. Thus, the infalling material formed a tall, narrow ridge of material. On a larger, more massive body, this ridge would not be so tall (relative to the body) because gravity would cause it to flatten out. But Pan's gravity is so feeble that the ring material simply settles onto Pan and builds up. Other dynamical forces keep the ridge from growing indefinitely.
These views are also presented in stereo (3-D) in PIA21435. The images are presented here at their original size.
The views were acquired by the Cassini narrow-angle camera at distances of 15,275 miles or 24,583 kilometers (left view) and 23,199 miles or 37,335 kilometers (right view). Image scale is 482 feet or 147 meters per pixel (left view) and about 735 feet or 224 meters per pixel (right view).
See PIA09868 and PIA11529 for more distant context views of Pan.
The Cassini-Huygens 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.
Pan Anaglyph (3-D)
Cassini Reveals Strange Shape of Saturn's Moon Pan
For more information about the Cassini-Huygens mission visit https://saturn.jpl.nasa.gov and 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, Text, Credits: NASA/Martin Perez/JPL-Caltech/Space Science Institute.
Best regards, Orbiter.ch
Publié par Orbiter.ch à 10:56