2019 October 4
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.