                        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.

                              2025 September 28
   Part of a large rock on Mars is shown being mostly orange. On the rock
   are several irregular light-colored areas surrounded by a dark border.
        The spots are only millimeters across but might be a remnant
    biosignature of ancient Martian life. Please see the explanation for
                         more detailed information.

                       Leopard Spots on Martian Rocks
          Image Credit: NASA, JPL-Caltech, MSSS, Perseverance Rover

   Explanation: What is creating these unusual spots? Light-colored spots
   on Martian rocks, each surrounded by a dark border, were discovered
   last year by NASA's Perseverance Rover currently exploring Mars. Dubbed
   leopard spots because of their seemingly similarity to markings on
   famous Earth-bound predators, these curious patterns are being studied
   with the possibility they were created by ancient Martian life. The
   pictured spots measure only millimeters across and were discovered on a
   larger rock named Cheyava Falls. The exciting but unproven speculation
   is that long ago, microbes generated energy with chemical reactions
   that turned rock from red to white while leaving a dark biosignature
   ring, like some similarly appearing spots on Earth rocks. Although
   other non-biological explanations have not been ruled out, speculation
   focusing on this potential biological origin is causing much intrigue.

                       Tomorrow's picture: comet comet
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       Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
            NASA Official: Amber Straughn Specific rights apply.
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                           NASA Science Activation
                             & Michigan Tech. U.

