Astronomy Picture of the Day

   [1]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
   [2]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 / [3]Science Source Images

   Explanation: Is this an alien? Probably not, but of all the animals on
   Earth, the [4]tardigrade might be the best candidate. That's because
   [5]tardigrades are known to be able to go for decades without food or
   water, to survive temperatures from near [6]absolute zero to well above
   the boiling point of water, to survive pressures from near zero to well
   above that on [7]ocean floors, and to survive direct exposure to
   dangerous [8]radiations. The far-ranging survivability of these
   [9]extremophiles was [10]tested in 2011 outside an orbiting space
   shuttle. [11]Tardigrades are so durable partly because they can repair
   their own [12]DNA and reduce their body water content to a few percent.
   Some of these [13]miniature water-bears almost became extraterrestrials
   in 2011 when they were launched toward to the Martian moon [14]Phobos,
   and again in 2021 when they were launched toward Earth's own moon, but
   the [15]former launch failed, and the [16]latter landing crashed.
   [17]Tardigrades are more common than [18]humans across most of the
   Earth. [19]Pictured here in a color-enhanced [20]electron micrograph, a
   millimeter-long tardigrade crawls on [21]moss.

   Your Sky Surprise: [22]What picture did APOD feature on your birthday?
                                 (post 1995)
                      Tomorrow's picture: sea blue sky
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    Authors & editors: [34]Robert Nemiroff ([35]MTU) & [36]Jerry Bonnell
                                 ([37]UMCP)
          NASA Official: Phillip Newman [38]Specific rights apply.
              [39]NASA Web Privacy Policy and Important Notices
                A service of: [40]ASD at [41]NASA / [42]GSFC,
                         [43]NASA Science Activation
                           & [44]Michigan Tech. U.

References

   1. https://apod.nasa.gov/apod/archivepix.html
   2. https://apod.nasa.gov/apod/image/2305/tardigrade_eyeofscience_960.jpg
   3. http://www.sciencesource.com/
   4. https://en.wikipedia.org/wiki/Tardigrade
   5. http://www.youtube.com/watch?v=6H0E77TdYnY
   6. https://en.wikipedia.org/wiki/Absolute_zero
   7. https://en.wikipedia.org/wiki/Seabed
   8. https://srag.jsc.nasa.gov/SpaceRadiation/What/What.cfm
   9. https://apod.nasa.gov/apod/ap090830.html
  10. http://tardigradesinspace.blogspot.com/
  11. http://www.youtube.com/watch?v=7W194GQ6fHI
  12. https://apod.nasa.gov/apod/ap120821.html
  13. https://bigthink.com/surprising-science/scientists-finally-figure-out-why-the-water-bear-is-nearly-unstoppable/
  14. https://apod.nasa.gov/apod/ap121028.html
  15. https://en.wikipedia.org/wiki/Living_Interplanetary_Flight_Experiment
  16. https://en.wikipedia.org/wiki/Beresheet
  17. http://serc.carleton.edu/microbelife/topics/tardigrade/index.html
  18. https://apod.nasa.gov/apod/ap190818.html
  19. https://www.custom-images.sciencesource.com/science-source-blog/2018/4/30/water-bears-tardigrades-pmr52
  20. https://en.wikipedia.org/wiki/Electron_micrograph
  21. https://en.wikipedia.org/wiki/Moss
  22. https://apod.nasa.gov/apod/calendar/allyears.html
  23. https://apod.nasa.gov/apod/ap230520.html
  24. https://apod.nasa.gov/apod/archivepix.html
  25. https://apod.nasa.gov/apod/lib/apsubmit2015.html
  26. https://apod.nasa.gov/apod/lib/aptree.html
  27. https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search
  28. https://apod.nasa.gov/apod/calendar/allyears.html
  29. https://apod.nasa.gov/apod.rss
  30. https://apod.nasa.gov/apod/lib/edlinks.html
  31. https://apod.nasa.gov/apod/lib/about_apod.html
  32. https://asterisk.apod.com/discuss_apod.php?date=230521
  33. https://apod.nasa.gov/apod/ap230522.html
  34. http://www.phy.mtu.edu/faculty/Nemiroff.html
  35. http://www.phy.mtu.edu/
  36. https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html
  37. http://www.astro.umd.edu/
  38. https://apod.nasa.gov/apod/lib/about_apod.html#srapply
  39. https://www.nasa.gov/about/highlights/HP_Privacy.html
  40. https://astrophysics.gsfc.nasa.gov/
  41. https://www.nasa.gov/
  42. https://www.nasa.gov/centers/goddard/
  43. https://science.nasa.gov/learners
  44. http://www.mtu.edu/