Scientists Pin Down What Time It Is on Mars — and Why It Matters

We Now Have a Baseline for Martian Time

Knowing the local time on another planet is more than a curiosity: it will be essential for navigation, communications, and surface operations as humans and robots travel beyond Earth. Researchers at the National Institute of Standards and Technology (NIST) — Bijunath Patla and Neil Ashby — have calculated how identical clocks on Mars would run compared with identical clocks on Earth, and published their results in The Astronomical Journal.

Why the Question Isn’t Simple

As a first-order matter, a Martian solar day (a sol) is roughly 40 minutes longer than an Earth day, and a Martian year is nearly twice as long. Beyond these differences, Einstein’s theory of relativity must be accounted for: both gravitational potential and relative motion affect clock rates. Stronger gravity slows clocks; weaker gravity lets them run faster. Motion (special-relativistic time dilation) also shifts rates depending on orbital speed.

What the Team Calculated

Patla and Ashby chose a reference point on the Martian surface and evaluated the combined gravitational influences of Mars itself plus the sun, Earth and our moon. Mars’s surface gravity is about one-fifth that of Earth’s, which tends to make Martian clocks run faster. But Mars’s more eccentric orbit means the sun’s pull — and the planet’s orbital speed — vary more across the year, producing additional, time-varying corrections.

“Its distance from the sun and its eccentric orbit make the variations in time larger. A three-body problem is extremely complicated. Now we're dealing with four: the sun, Earth, the moon and Mars,” said Bijunath Patla.

After accounting for gravitational and kinematic effects, the team found that identical clocks on Mars would tick, on average, about 477 millionths of a second (477 µs) faster per Martian day (sol) than identical clocks on Earth. That average offset is not constant: it can vary by up to 226 millionths of a second (226 µs) per sol over the course of a Martian year, because of changing gravitational potentials and orbital motion.

Why Millionths of a Second Matter

Although millionths of a second sound vanishingly small, they are significant for precision navigation and timing systems. Terrestrial global navigation satellite systems (GNSS) like GPS depend on extremely accurate clocks; errors of microseconds translate into position errors of hundreds of metres. Any future Martian navigation network or timing standard will need the same relativistic corrections and the baseline numbers Patla and Ashby provide.

Patla and Ashby’s calculations give engineers and mission planners a concrete starting point for designing clocks, navigation protocols and communications systems for Mars missions — from spacecraft tracking to rover operations and interplanetary communications.

Bottom Line

The study gives a practical, relativistically corrected baseline for a Martian time standard: clocks on Mars run a few hundred microseconds faster per sol than identical Earth clocks, with predictable variations through the Martian year. That precision will be crucial for future exploration and any off-world navigation systems.