There is talk in the scientific community of a manned Mars mission: sending an elderly couple to slingshot past Mars and return to Earth as a trial mission, toward eventual other missions that will land there in the future. The mission would last around 300 days.

What would be the halachic challenges that the couple could face on a day-to-day basis? (This question doesn't ask whether space exploration/travel is halachically desirable.)

  • I assume you mean challenges that are unique to space travel (meaning kosher food is not the answer you are looking for).
    – Double AA
    Commented Aug 21, 2013 at 22:29
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    Good thing they are elderly or Mikva would be a big problem.
    – Double AA
    Commented Aug 21, 2013 at 22:30
  • @DoubleAA see judaism.stackexchange.com/questions/26921/… Commented Aug 21, 2013 at 22:40
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    Perhaps kosher food would be a problem. Space food often consists of powdered food that needs hydration. It may not be possible, for health reasons, to provide a balanced diet using novel space food storage techniques. I don't know!
    – bondonk
    Commented Aug 21, 2013 at 23:01
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    I know there are disagreements over how often you would need to pray in space. This could cause problems, especially since you would be required to keep to an exercise regime when on board. Chagim?
    – bondonk
    Commented Aug 21, 2013 at 23:03

1 Answer 1


This answer will focus just on those aspects which are unique to a Mars Mission, as those relating to any long-distance visit to a foreign locale have been dealt with elsewhere.

Travel in Space

Life on Mars

These questions can be summarized as follows: For those Halakhot which depend on astronomical \ planetary variables, do we follow Earth or local (Martian) values?

  • Calendar. A day on Mars is about 40 minutes longer than an Earth day. Does one go based on the the Mars day or the Earth day?
    • If we do go by the Martian day, then Mars will fall behind at a rate of about 1 day per (Earth) month. The Martian calendar will need to be re-calculated (subtract one day per month, etc) to stay in sync with the Earth calendar.
  • Kiddush Levana. Mars has two moons, Phobos and Deimos. When would one say Kiddush Levana? Would one say it once per orbit for each of these moons, once per Martian "month" (which would probably be divorced from the lunar cycles), or follow the Earth tradition? Perhaps one wouldn't say Kiddush Levana at all.
  • Zmanim. Seems pretty straight-forward, as Halakhic time is based on location and length of daylight anyways.
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    Wikified. Feel free to add.
    – Shmuel
    Commented Apr 20, 2014 at 23:24
  • I don't see why living on Mars you would go by the Martian moons for kiddish levana
    – bondonk
    Commented Apr 23, 2014 at 20:50
  • כל מצוה שהיא תלויה בארץ אינה נוהגת אלא בארץ; ושאינה תלויה בארץ נוהגת בין בארץ בין בחוצה לארץ Kiddushin 27, Mishna
    – Shmuel
    Commented Apr 24, 2014 at 1:08
  • @bondonk Because you can see their phases?
    – Double AA
    Commented Apr 24, 2014 at 3:55
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    @Shmuel with creativity you could say that 'lo bashamayim he' means mitzvot don't apply on mars! Its difficult to deviate from the traditional understanding on the moon being ours but it could be.
    – bondonk
    Commented Apr 24, 2014 at 4:22

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