Timekeeping on Mars facts for kids

This image shows how long seasons last on Mars (red) compared to Earth (blue).

Have you ever wondered what time it is on Mars? Since humans haven't built cities there yet, there isn't one official way to tell time. But scientists and space missions need to keep track of days and years on the Red Planet. They use special methods to measure time, especially for planning missions.

Mars is a lot like Earth in some ways. It spins on its axis and has a tilt, just like Earth. This means Mars also has four seasons: spring, summer, autumn, and winter. However, Mars's orbit around the Sun is more oval-shaped than Earth's. This makes its seasons last for different amounts of time.

A day on Mars is called a "sol". It's only a little bit longer than an Earth day, less than an hour more. But a Martian year is much longer, almost twice as long as an Earth year!

Martian Days: Sols

What is a Sol?

A "sol" is what scientists call a day on Mars. It helps them avoid mixing up Martian days with Earth days. This term became popular during NASA's Viking missions in 1976.

A Martian day is just a little longer than an Earth day. It lasts about 24 hours and 39 minutes. So, if you lived on Mars, your day would be about 39 minutes longer than it is here on Earth!

Because a sol is longer, a Martian hour, minute, and second are also a bit longer than ours. For example, a Martian hour is about 1 hour and 1 minute in Earth time.

Counting Martian Days

Scientists use a special way to count days on Mars, similar to how astronomers count days on Earth. It's called the Mars Sol Date (MSD).

The MSD is a continuous count of sols. It started way back on December 29, 1873. This system helps scientists keep track of time for long-term studies of Mars.

Clocks and Time Zones on Mars

Mission Clocks in Action

When spacecraft land on Mars, their teams on Earth start working on "Mars time." This means their work schedule matches the local time at the landing site on Mars.

Since a Martian day is about 40 minutes longer than an Earth day, the team's schedule shifts a little later each Earth day. Some team members even wear special wristwatches that show Martian time!

This "Mars time" helps them plan daily tasks. For example, solar panels need daylight to work. Also, temperatures on Mars change very quickly at sunrise and sunset. This is because Mars doesn't have a thick atmosphere or oceans like Earth to keep things steady.

This image shows the analemma for Mars, which illustrates how the Sun's position in the sky changes throughout the year.

How Missions Count Sols

When a NASA spacecraft lands on Mars, it starts counting sols. Most missions, like Viking, Phoenix, Curiosity, InSight, and Perseverance, call the landing day "Sol 0".

However, some missions, like Pathfinder and the Mars Exploration Rovers (Spirit and Opportunity), called their landing day "Sol 1".

Each mission uses its own local time. This time is set to match the sun's position at their landing spot. China's Zhurong rover likely uses a similar system.

Mars's Prime Meridian

Just like Earth has a prime meridian (the line of 0 degrees longitude), Mars has one too. It passes through a small crater called Airy-0.

Scientists agreed on this prime meridian for Mars a long time ago, even before Earth had its own official one! This helps everyone know where different places are on the planet.

However, Mars doesn't have official time zones like Earth. Each mission uses the local time at its landing spot. It's similar to how cities on Earth used their own local times before standard time zones were created.

A Standard Mars Time?

Scientists have thought about creating a standard "Coordinated Mars Time" (MTC). This would be like Universal Time (UT1) on Earth. It would be based on the mean solar time at Mars's prime meridian.

While MTC is a good idea for the future, it hasn't been used for missions yet. This is partly because the exact location of Airy-0 wasn't known perfectly at first. But as we explore Mars more, a standard time might become very useful.

Martian Years and Seasons

This diagram by Percival Lowell compares the length of Martian and Earth years.

How Long is a Martian Year?

A year on Mars is much longer than on Earth. It takes Mars about 687 Earth days to orbit the Sun. That's almost twice as long as our year!

In Martian days (sols), a year is about 669 sols long. Because Mars's orbit is more oval-shaped, its seasons don't all last the same amount of time.

For example, spring in the northern part of Mars is the longest season, lasting 194 sols. Autumn in the northern part is the shortest, at only 142 sols.

Seasons on Mars

Just like Earth, Mars has four seasons: spring, summer, autumn, and winter. These seasons start at specific points in Mars's orbit around the Sun.

Scientists use something called "solar longitude" (L_s) to mark the start of each season. Each season covers 90 degrees of this longitude.

Naming Martian Years

To keep track of Martian years, scientists use a special numbering system. They call the Martian year that started on April 11, 1955, "Mars Year 1" (MY1).

This system helps them compare climate data and events on Mars over long periods. For example, a big dust storm happened in 1956, which was during MY1.

The current Martian year is MY38, which started on November 12, 2024. MY37 ended on November 11, 2024. The next Martian year, MY39, will begin on September 30, 2026.

Imagining Martian Calendars

If people ever live on Mars, they will need a calendar. Just like we use the Gregorian calendar on Earth, Martians would need a way to keep track of dates, anniversaries, and seasons.

Many scientists and thinkers have proposed different ideas for a Martian calendar over the years. These calendars try to fit the longer Martian year into a system of months and weeks.

For example, in the past, astronomers like Percival Lowell and William Henry Pickering suggested calendars. They tried to make Martian dates similar to Earth dates, but adjusted for the longer year.

One interesting idea is the Darian calendar, proposed by Thomas Gangale. It has 24 months to fit the longer Martian year. This calendar tries to keep months a similar length to Earth months.

These ideas show how people are already thinking about what life might be like on Mars. A good calendar would be key for future Martian explorers and settlers.

Mars Time in Stories and Movies

Many authors and filmmakers have imagined what time would be like on Mars. They often create unique calendars and ways to measure days and years for their Martian worlds.

• In Percy Greg's old novel Across the Zodiac (1880), Martian days were divided into parts based on the number 12.
• Robert A. Heinlein's book Red Planet (1949) used a 24-month calendar. It mixed Earth months with new ones like Ceres and Zeus.
• In Arthur C. Clarke's The Sands of Mars (1951), days of the week were the same as Earth's, but months were much longer, lasting 50 to 60 days.
• Philip K. Dick's Martian Time-Slip (1964) and Kim Stanley Robinson's Mars Trilogy (1992–1996) imagined clocks that paused for 39.5 minutes at midnight. This "timeslip" became a special moment for Martians.
• The Darian calendar (a real proposal) has even appeared in science fiction, like in the Star Trek book Watching the Clock and the novel The Quantum Thief.
• In Andy Weir's popular novel The Martian (2011) and the movie based on it, the main character counts his days using "sols." This helps show how long he is stranded on Mars.
• The TV series For All Mankind shows characters on a Mars base wearing special "Mars time" wristwatches, just like real scientists use today.

See also

• Astronomy on Mars
• Universal Time
• Coordinated Universal Time