PIA17184: Encroaching Shadow

 Encroaching Shadow

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Annotated version


This Cassini narrow-angle camera image – one of those acquired in the survey conducted by the Cassini imaging science team of the geyser basin at the south pole of Enceladus – was taken as Cassini was looking across the moon’s south pole. At the time, the spacecraft was essentially in the moon’s equatorial plane. The image scale is 1280 feet (390 meters) per pixel and the sun-Enceladus-spacecraft, or phase, angle is 162.5 degrees.

The image was taken through the clear filter of the narrow angle camera on Nov. 30, 2010, 1.4 years after southern autumnal equinox. The shadow of the body of Enceladus on the lower portions of the jets is clearly seen.

In an annotated version of the image, the colored lines represent the projection of Enceladus’ shadow on a plane normal to the branch of the Cairo fracture (yellow line), normal to the Baghdad fracture (blue line) and normal to the Damascus fracture (pink line).

Post-equinox images like this, clearly showing the different projected locations of the intersection between the shadow and the curtain of jets from each fracture, were useful for scientists in checking the triangulated positions of the geysers, as described in a paper by Porco, DiNino, and Nimmo, and published in the online version of the Astronomical Journal in July 2014: dx.doi.org/10.1088/0004-6256/148/3/45.

A companion paper, by Nimmo et al. is available at: dx.doi.org/10.1088/0004-6256/148/3/46.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. NASA’s 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 saturn.jpl.nasa.gov and www.nasa.gov/cassini. The Cassini imaging team homepage is at ciclops.org.

Image Credit: NASA/JPL-Caltech/Space Science Institute

Image Addition Date: 2014-07-28

Source: NASA’s Planetary Photojournal: Image No. PIA17184