How Time Ticks on Mars — NIST Finds Clocks Run 477 Microseconds Faster Than on Earth

Researchers at the National Institute of Standards and Technology (NIST) have calculated that identical clocks on Mars tick about 477 microseconds per day faster than those on Earth after accounting for gravity, orbital motion, and the influence of nearby bodies. While tiny, this difference matters for high-precision navigation, communications, and future crewed missions to the Red Planet.

Why clocks run at different rates

Einstein’s general theory of relativity ties the rate at which time passes to the strength of gravity and to motion. Clocks in weaker gravitational fields or moving at different speeds run at slightly different rates. On Earth, these effects are already important: for example, GPS satellite clocks, orbiting roughly 12,544 miles above Earth, gain about 45.7 microseconds per day relative to ground clocks unless engineers correct for relativity.

What makes Mars special

Mars’s surface gravity is roughly five times weaker than Earth’s, which by itself would make Martian clocks run faster. But gravity is only part of the story. Mars’s orbital speed, its more eccentric 687-day orbit (compared with Earth’s more circular path), and the gravitational pull of the Sun, Earth and Moon all affect clock rates. Adding Mars to the existing Sun–Earth–Moon system creates a more complex many-body problem that demands careful modeling.

“Adding Mars to the Sun–Earth–Moon system turns an already difficult three-body problem into something even more complex,” said NIST physicist Bijunath Patla, a co-author of the study. “We defined a Martian reference surface analogous to Earth’s sea level and included all relevant gravitational and kinematic effects to produce a practical timescale for Mars.”

NIST physicists Bijunath Patla and Neil Ashby built a Martian reference surface similar to terrestrial sea level at the equator and incorporated gravitational potentials, orbital velocities, and perturbations from neighboring bodies. Their computations yield an operational timescale: Martian surface clocks run about 477 microseconds per day faster than equivalent Earth-surface clocks.

Practical implications

Although 477 microseconds per day is extremely small, advanced systems can be sensitive to such offsets. Modern telecommunications systems and next-generation network technologies often require synchronization at or below the sub-microsecond level; 5G networks, for example, may need timing accuracy on the order of a tenth of a microsecond. For planetary missions, precise timekeeping will be critical for navigation, scientific coordination, and maintaining coherence between surface assets and Earth-based control.

Today, signal travel times between Earth and Mars already impose minutes of latency—communications with current rovers can take more than 24 minutes round-trip depending on planetary positions. But future relay networks, coupled with accurate relativistic timekeeping, could minimize synchronization errors and help make interactions with crews and instruments appear far more immediate despite the physical signal delay.

Patla added, “If you achieve tight synchronization, interactions with Martian explorers can approach real-time behavior from an information perspective, even while light-speed delays remain.”

Looking ahead

NIST’s Martian timescale builds on prior work such as their lunar timekeeping framework and offers a template for establishing timing standards for other planets and moons as human exploration expands across the solar system. The result is both a practical tool for mission planners and a clear demonstration of relativity’s everyday importance for space systems.