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.

                               2021 February 3

          Found on the Moon: Candidate for Oldest Known Earth Rock
       Video Credit: NASA, Astromaterials 3D, Erika Blumenfeld et al.

   Explanation: Was the oldest known rock on Earth found on the Moon?
   Quite possibly. The story opens with the Apollo 14 lunar mission. Lunar
   sample 14321, a large rock found in Cone crater by astronaut Alan
   Shepard, when analyzed back on Earth, was found to have a fragment that
   was a much better match to Earth rocks than other Moon rocks. Even more
   surprising, that rock section has recently been dated back 4 billion
   years, making it older, to within measurement uncertainty, than any
   rock ever found on Earth. A leading hypothesis now holds that an
   ancient comet or asteroid impact launched Earth rocks into the Solar
   System, some of which fell back to the Moon, became mixed with heated
   lunar soil and other rocks, cooled, and re-fragmented. The video
   features an internal X-ray scan of 14321 showing multiple sections with
   markedly different chemistries. Moon rocks will continue to be studied
   to learn a more complete history of the Moon, the Earth, and the early
   Solar System. Friday marks the 50th Anniversary of the Apollo 14
   landing on the Moon.

                       Tomorrow's picture: open space
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       Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
            NASA Official: Phillip Newman Specific rights apply.
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