What Is a Sol? How Long Is a Day on Mars?
A sol is a day on Mars, 24 hours 39 minutes and 35 seconds long. Here is how Mars time works, why missions use it and how a Martian year compares.
A sol is one solar day on Mars: the time from one noon to the next. It lasts 24 hours, 39 minutes and 35 seconds, only about 40 minutes longer than a day on Earth.
Why missions count in sols
Rovers run on sunlight-driven routines: they wake up, charge or warm up, drive and do science during the Martian day. So mission teams count time in sols, starting from sol 0, the day of landing. When you read that a photo was taken on "sol 1,000", it means a thousand Martian days after touchdown.
For the first months of a mission, engineers on Earth often live on Mars time too. Because a sol is 40 minutes longer, their work shift moves later every day, so after a few weeks they start work in the middle of the night.
Mars local time
Each place on Mars has its own local time, just like time zones on Earth. Mission teams use Local Mean Solar Time (LMST). In Trawers, the clock in the header shows the LMST at your rover, so you can tell whether it is morning or night where you are driving.
How long is a year on Mars?
Mars takes 687 Earth days to go around the Sun, which is about 669 sols. Its seasons are roughly twice as long as Earth's and uneven, because the Martian orbit is more stretched out than ours.
Quick numbers
- 1 sol = 24 h 39 min 35 s
- 1 Mars year = 687 Earth days ≈ 669 sols
- 1 Earth day ≈ 0.97 sols
Land on Mars in Trawers and watch the sols tick by at your landing site.