When a robot on Mars does something like take a picture, how does it date that file? I imagine that the responsible laboratory is a possible referential, correct?

Is it possible / does it make sense to create a common reference to compare data (for example) made in different points of the solar system, so that it can be chronologically ordered in an easy way?

In my mind if we are going to have a community on Mars, we will not be able to use referential from here to the files made there, so would it be necessary to have a common referential? something like how many laps the sun went around itself from a zero mark?!?

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    $\begingroup$ Computers don't use unreliable things like the rotation of the Earth for measuring time here, so why would they do that on Mars, especially as that would - as you point out - cause a source of confusion. $\endgroup$
    – user20636
    Jan 12, 2019 at 21:36
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    $\begingroup$ A lot depends of how accurate you want to be. GR makes standard-second clocks on Mars separate from standard-second clocks by a large fraction of a second over a year. $\endgroup$ Jan 13, 2019 at 4:45

2 Answers 2


Curiosity's computer tracks the number of seconds from an epoch [January 1, 2000 CE], landing happened at 397502503. The mission calendar uses sols (Martian days) counting from the landing day = sol 0.

(from The Design and Engineering of Curiosity, Emily Lakdawalla)

I see no reason not to use Earth time as the baseline in a Mars community. Anything else would massively complicate things for no benefit.

  • $\begingroup$ RE using Earth or Mars time - clock drift relative to local solar day. Sitting on Earth sticking with Earth time may make sense, but I suspect within a few weeks Martians will start getting annoyed at figuring out the shifting sun/clock relationship. Even if business gets done by Earth clock, a local time system is inevitable. $\endgroup$
    – Saiboogu
    Jan 12, 2019 at 17:05
  • $\begingroup$ Sure, you'll get Martian days of 24.5 hours each, and time zones. But they'll still be based on one of Earth's time standards. $\endgroup$
    – Hobbes
    Jan 12, 2019 at 17:48
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    $\begingroup$ Note: the epoch in question appears, by counting back, to actually be January 1, 2000. $\endgroup$ Jan 12, 2019 at 19:12

The timescale used for photos taken on Mars by a robotic lander may be chosen as apropriate. It should be guaranteed that two images taken at different times always get different time stamps. The clock tick used should be so fast that two images taken at minimal time distance get different time stamps, at least by one clock tick.

During the lifetime of the robot time stamps should not repeat. The time stamps should be convertable to time and date used on Earth. The time interval between two photos should be convertable to days, hours, minutes and seconds.

It should be possible to calculate the time interval between the Martian sunrise and the time stamp of the photo.


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