The numbers
The near match with an Earth day is almost accidental: other planets have wildly different day lengths. That closeness is what makes Mars convenient for humans - and also creates the very problem with those forty minutes.
The third tile changes everything else. The year is almost twice as long, so the seasons last twice as long too: winter on Mars lasts about six Earth months, and work has to be planned around that.
Living by Martian time
Teams running rovers switched to sols: each day, their shift began forty minutes later. After two weeks, the workday had moved to the other half of the day - like flying across a time zone every day and a half, but without ever landing.
People described it as a grueling schedule: constant sleepiness, missing out on family life, and working at 3 a.m. Earth time. For some missions, special clocks were made that ran on Martian time.
The reason was sunlight. A rover runs on solar panels, so teams plan its day so that instructions arrive in the Martian morning - otherwise the vehicle sits idle for an entire sol.
There is also a second delay, unrelated to the length of a day. A signal takes anywhere from a few minutes to more than twenty minutes one way, so it is impossible to control the vehicle in real time: it receives a program for the entire day all at once.
How much longer is a Martian day than an Earth day?
Why did teams switch to Martian time?
Sources
- A Martian day lasts about 24 hours 39 minutes, and a Martian year lasts about 687 Earth days
- rover operations teams switched to local time, which gradually shifted their work schedule relative to Earth
Next in the “Mars” series
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