Einstein was right: Time moves faster on Mars, and that has real implications for future explorers
A recent analysis shows that clocks on Mars run slightly faster than those on Earth. When compared from Earth, Martian clocks advance about 0.477 milliseconds (477 microseconds) per Martian day. This difference could be a key piece in designing an interplanetary network capable of coordinating communications across the solar system.
As humanity’s presence beyond Earth expands—NASA’s Artemis program aims to establish long-term presence on the Moon and beyond—the idea of a standard time system for different worlds becomes increasingly important. A universal clock for each celestial location would help astronauts navigate unfamiliar terrain and stay in sync with Earth-based operations.
Time is relative
The passage of time on any world depends on both its speed through space and its gravity. A 2024 study found that clocks on the Moon tick about 56 microseconds faster per Earth day than clocks on Earth. Building on that work, researchers Neil Ashby and Bijunath Patla of the National Institute of Standards and Technology (NIST) in Boulder, Colorado, turned to Mars.
First, they defined an areoid on Mars—the equivalent of Earth’s sea level—as a reference surface. Using physics-based equations, they calculated how time would flow at the Martian areoid, given Mars’ gravity and its orbital motion relative to Earth. Mars’ slower orbital speed would naturally tend to slow its clocks, but its much weaker surface gravity (about one-fifth that of Earth at the areoid) speeds time up more than the orbital slow-down.
Orbital shape and nearby giants matter
However, the analysis initially left out the shapes of the orbits. Mars travels along a more elongated, egg-shaped orbit than Earth’s, shaped by gravitational interactions with the Sun and with Earth’s Moon. The moons Deimos and Phobos are tiny by comparison and have little direct impact on the time calculations, but the researchers included Mars’ orbital eccentricity, the Sun’s gravity, and Earth–Moon gravity in their models.
Clocks on Mars run faster from Earth’s vantage point
The outcome: Martian clocks appear to tick faster than Earth-based clocks by an average of 477 microseconds per Earth day when observed from Earth. Interestingly, this offset isn’t constant; it varies by about 226 microseconds from day to day over a Martian year, driven by the changing shape of Mars’ orbit and the shifting gravitational tugs of nearby bodies.
There’s more—regular, but irregular, fluctuations
Additionally, the team found an extra 40-microsecond variation over seven Mars synodic periods—the time it takes for Mars to return to the same position in the sky relative to Earth and the Sun. These fluctuations were larger than the researchers anticipated and add complexity to any attempt to keep perfectly synchronized interplanetary timekeeping.
A path toward an interplanetary time standard
Published on December 1 in The Astronomical Journal, the findings establish a baseline for future tests of relativity and fundamental physics by comparing how spacetime behaves across worlds. They also form a practical foundation for future interplanetary communications networks. That said, the team notes that long-term precision remains imperfect: tiny unmodeled shifts in planetary motions can introduce errors of roughly 100 nanoseconds per day, potentially requiring periodic clock resynchronization.
Beyond the basics, the study acknowledges remaining uncertainties. It did not fully account for precession of planetary orbits or gradual wobbles in each planet’s orientation, nor did it incorporate the ways Earth’s and Mars’ mass distributions (their gravitational quadrupole moments) influence timekeeping. These omissions mean the current calculations are a solid baseline but will need refinement as models grow more comprehensive.
Why this matters
As missions grow bolder and missions to establish settlements become more credible, having consistent, well-understood time standards across planets will be crucial. It would enable faster, more reliable interplanetary communications and coordination, helping crews operate safely and efficiently in environments far from Earth.
Controversial takeaway and questions for readers
Some may wonder whether pursuing separate clocks for each world is worth the complexity, or if a single universal time would be simpler to manage. Do you think Earth-based time standards should be adapted for Mars and beyond, or would a modular, orbit- and gravity-aware system offer clearer advantages? And as our robots and humans venture farther, should timekeeping be prioritized for navigation, communications, or a deeper test of fundamental physics? Share your thoughts in the comments.
