Designing a Martian Clock

Telling Time on the Red Planet

A friend sent me an article yesterday discussing the potential problems that astronauts will have living on Mars. One of the problems that I only minimally considered was the difficulty of living in an environment that only approximates the day/night cycle on Earth. Mars has a day that is 24 hours and 39 minutes long which makes it a nightmare for prolonged missions.

The reason it’s so difficult for extended missions is that the communication channels between Earth and Mars need to stay constant. This means that for ground crews the day is constantly 39 minutes longer. For robotic missions it’s a little easier but for humans it plays hell with their circadian rhythms.

Imagine that normally you wake up at 6am to work. Every 18 days you would have to wake up at 6pm to go to work. Since we’re set to Earth normal, it’s a difficult problem to tackle but not unconquerable.

Andrew Louden, a Professor of Biology at the University of Manchester said:

“The rotation speed of Mars may be within the limits of some people’s internal clock, but people with short running clocks, such as extreme morning types, are likely to face serious intractable long-term problems, and would perhaps be excluded from any plans NASA has to send humans to Mars.
If we ever do get to the Red Planet, I suspect we will be faced with body clock problems; those people with abnormally slow body clocks would be best suited to living there.”

Past Mars missions have used clocks that are 2.7% slower than Earth-normal or they’ve paused at midnight for 39 minutes in order to account for the rotational difference. Coordinated Mars Time (MCT) was proposed in the 1830s to account for the time difference to Earth. It was adopted by Mars24, NASA Goddard’s Institute for Space Sciences, to account for the time of the different missions. It has yet to be adopted as an official time standard. Currently there is no given standard for timekeeping on Mars. It is all thought of in relation to Sols, or solar Martian days. Every mission has it’s own day that starts on the landing on Sol 0, and continues from there.


Why is time so important? Space missions depend immensely on time. As spacecraft get further from Earth, the on-board system clock dictates when course-corrections are made, sensors are deployed, and landing procedures are initiated. In addition, the mission clock also determines communication with Earth and operating time on a planet. That is why it is essential to have a good timekeeping system, particularly for when humanity lands on the red planet.

So let’s figure out some method by which Mars has it’s own clock. Let’s design for a given environment on the planet, not just on the basis of Earth-normal. After all, the division of 24 hours and 60 minutes is merely arbitrary and designed to mathematically segment each day into equal parts. Let’s make a clock that is designed mathematically for Mars.

A Martian solar day is 24 hours 39 minutes and 35.24409 seconds. That’s 88,775.24409 seconds per day. A Martian year is 668.5991 days. This varies depending on hemisphere but I’ve given the global averages (which is the same way Earth dictates time).

When you pare down to the seconds (SI standard) per day by equal increments of 25, you get 3,551.0097636 seconds. The decimals are always important in regards to time because they dictate the corrections later on. Earth habitually has a four day leap year, let’s see if we can do better for Mars. Factoring this down again in equal increments yields divisors of 67 and 53. Therefore a Martian day would be 25 “hours” 67 “minutes” and 53 seconds by this accounting. The reason I put quotations around the hours and minutes but not the seconds is because this clock is dictated by the seconds as a standard. The hours are dependent on the minutes and each minutes is 53 seconds. Based on this accounting, every 103 days needs a leap second.

This actually makes a good deal of sense because Mars has a lower gravity than Earth. Any athletic event performed on Mars would receive the benefit of this lower gravity and therefore be much faster, stronger, etc. The faster the clock fits the faster Martian.

So how does this work for each year? How many of these days are in each year? Is there a better system to allow for a Martian calendar?

Let’s remove all standards except for seconds. This means that we can divide by weeks and months as well. A Martian year is 59,355,048.3009 seconds and the year is 668.5991 days. Since we’ve already figured out that each day is 25 “hours” with each “hour” as 67 “minutes” and each minute as 53 seconds, let’s start figuring out how to equally divide the year into weeks and months.

The system works on a yearly basis but our current calendar would be wrong to use in this system. We need a fundamentally different “month” and “week.” The number of Martian days in a given year is 668.5991.

Let’s round down the total days to 668 “days.” There can be a yearly festival with a different day as a part of Martian culture. This can account for the last day of the year changing the time to equalize any remaining rounding errors in the yearly cycle.

The days factor into 4 and 167. What if instead of dividing by weeks and months, we also divided by seasons? Therefore Mars would have 4 seasons. A Martian season would be 167 days.

That 167 can be split into increments of 3 instances of 42 days and one of 41 days which would be the length of a Martian “month.” For each season of 167 days, there would be a total of 10 mutual events of Phobos passing in front of Deimos. At the end of each season, there would be one week with one less day.

Phobos and Deimos get mutual.

Each Martian “month” would have a maximum of 42 days. This could be divided into the standard 7 day per week but with 6 weeks per month. The Martian calendar would then have 16 months. There would be 12 months of 42 days and 4 months of 41 days.

Therefore the final breakdown of Martian time would be:

1 year = 668 days

4 seasons/year

4 months/season

6 weeks/month

7 days/week

25 hours/day

67 minutes/hour

53 seconds/minute

There would be a day each year in which a celebration would occur and the time would be reset. I suggest that this occur during the point at which Mars is closest to the sun. That is also the date at which the year begins.

In addition, there needs to be names for the four extra months. Also, since there is no current naming convention for weeks, the Martian weeks could also be named to keep track of the cycle.

Does anyone have suggestions for names for the months or weeks? Let me know. I’ll be putting together the electronics for a Martian clock and designing a calendar based on this system for a later post. ER.

Update: I found a Martian clockmaker here and will contact him to see if he has any advice about clockmaking for Mars.

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