                        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.

                                 2023 May 21
     An usual looking creature is pictured which may appear alien but is
    actually a Earth-dwelling tardigrade. The tardigrade has no apparent
   eyes, a light brown body, a circular gear-like snout, and claws at the
   end of its numerous feet. The tardigrade is seen perched on green moss.
          Please see the explanation for more detailed information.

                             Tardigrade in Moss
      Image Credit & Copyright: Nicole Ottawa & Oliver Meckes / Eye of
                       Science / Science Source Images

   Explanation: Is this an alien? Probably not, but of all the animals on
   Earth, the tardigrade might be the best candidate. That's because
   tardigrades are known to be able to go for decades without food or
   water, to survive temperatures from near absolute zero to well above
   the boiling point of water, to survive pressures from near zero to well
   above that on ocean floors, and to survive direct exposure to dangerous
   radiations. The far-ranging survivability of these extremophiles was
   tested in 2011 outside an orbiting space shuttle. Tardigrades are so
   durable partly because they can repair their own DNA and reduce their
   body water content to a few percent. Some of these miniature
   water-bears almost became extraterrestrials in 2011 when they were
   launched toward to the Martian moon Phobos, and again in 2021 when they
   were launched toward Earth's own moon, but the former launch failed,
   and the latter landing crashed. Tardigrades are more common than humans
   across most of the Earth. Pictured here in a color-enhanced electron
   micrograph, a millimeter-long tardigrade crawls on moss.

     Your Sky Surprise: What picture did APOD feature on your birthday?
                                 (post 1995)
                      Tomorrow's picture: sea blue sky
     __________________________________________________________________

       Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
            NASA Official: Phillip Newman Specific rights apply.
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                           NASA Science Activation
                             & Michigan Tech. U.

