                        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.

                               2019 October 4

                           InSight on a Cloudy Day
                Image Credit: NASA, JPL-Caltech, Mars InSight

   Explanation: Clouds drift through the sky as the light fades near
   sunset in this three frame animated gif. The scene was captured on sol
   145 beginning around 6:30pm local time by a camera on the Mars InSight
   lander. Of course, InSight's martian day, sol 145, corresponds to Earth
   calendar date April 25, 2019. Under the 69 centimeter (2.3 foot)
   diameter dome in the foreground is the lander's sensitive seismometer
   SEIS designed to detect marsquakes. Earthquakes reveal internal
   structures on planet Earth, and so tremors detected by SEIS can explore
   beneath the martian surface. In particular, two typical marsquakes were
   recorded by SEIS on May 22 (sol 173) and July 25 (sol 235). The subtle
   tremors from the Red Planet are at very low frequencies though, and for
   listening have to be processed into the audio frequency range. In the
   sped up recordings external noises more prevalent on cool martian
   evenings and likely caused by mechanical shifts and contractions have
   been technically dubbed dinks and donks.

                       Tomorrow's picture: moon shadow
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       Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
            NASA Official: Phillip Newman Specific rights apply.
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                             & Michigan Tech. U.

