Astronomy Picture of the Day

    Discover the cosmos! Each day a different image or photograph of our
      fascinating universe is featured, along with a brief explanation
                    written by a professional astronomer.

                                2020 April 27

                  Fresh Tiger Stripes on Saturn's Enceladus
           Image Credit: NASA, ESA, JPL, SSI, Cassini Imaging Team

   Explanation: How will humanity first learn of extraterrestrial life?
   One possibility is to find it under the icy surface of Saturn's moon
   Enceladus. A reason to think that life may exist there are long
   features -- dubbed tiger stripes -- that are known to be spewing ice
   from the moon's icy interior into space. These surface cracks create
   clouds of fine ice particles over the moon's South Pole and create
   Saturn's mysterious E-ring. Evidence for this has come from the robot
   Cassini spacecraft that orbited Saturn from 2004 to 2017. Pictured
   here, a high resolution image of Enceladus is shown from a close flyby.
   The unusual surface tiger stripes are shown in false-color blue. Why
   Enceladus is active remains a mystery, as the neighboring moon Mimas,
   approximately the same size, appears quite dead. A recent analysis of
   ejected ice grains has yielded evidence that complex organic molecules
   exist inside Enceladus. These large carbon-rich molecules bolster --
   but do not prove -- that oceans under Enceladus' surface could contain
   life. Another Solar System moon that might contain underground life is
   Europa.

          Experts Debate: How will humanity first discover ET life?
                 Tomorrow's picture: an almost solar system
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       Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
            NASA Official: Phillip Newman Specific rights apply.
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                      A service of: ASD at NASA / GSFC
                             & Michigan Tech. U.

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