Credit: ZME Science/Midjourney.

On Mars, clocks run slightly faster. Physicists at the National Institute of Standards and Technology (NIST) just calculated the precise difference. They found that, on average, clocks on Mars tick 477 microseconds faster every single day than clocks on Earth.

This temporal lag is a direct consequence of Albert Einstein’s Theory of General Relativity. The rule is simple: the weaker the gravity, the faster time passes. Mars’s surface gravity is a weakling, approximately five times weaker than Earth’s. That deficit speeds up time.

Four hundred seventy-seven microseconds sounds minuscule. It’s about one-thousandth of the time it takes you to blink. But for the advanced communication networks of the future, like 5G, this small discrepancy is absolutely critical. That sliver of time could also mean the difference between a rover’s successful landing and a disastrous miss.

If humanity wants a working colony on the Red Planet — a colony with synchronized communication and navigation — we first need to fix our watches.

A New Interplanetary “Time Zone”

The study led by NIST physicists Neil Ashby and Bijunath Patla dives deep into the tangled mathematics of relativity, orbital mechanics, and planetary gravity. Their work builds on decades of research into how time behaves under different gravitational and orbital conditions — first for the Moon, now for Mars.

On Earth, timekeeping depends on an intricate global network of atomic clocks, GPS satellites, and communication relays. But Einstein’s general relativity reminds us that gravity and motion bend time itself. The stronger the gravity, the slower a clock ticks. The faster something moves, the more its sense of time stretches.

Mars, sitting farther from the Sun and with surface gravity about one-fifth of Earth’s, lives in a weaker gravitational field. That makes its clocks run faster. But that’s not all. Mars’ highly eccentric orbit — much more elliptical than Earth’s — means its distance from the Sun changes more dramatically, subtly speeding or slowing time throughout its year.

Using data from NASA’s Mars Reconnaissance Orbiter and high-precision models of planetary motion, the researchers estimated that the Red Planet’s clocks gain an average of 477 microseconds per day, with variations of about 226 microseconds depending on where Mars is in its orbit. Previously, physicists at the Jet Propulsion Laboratory led by Slava Turyshev found that time runs faster on the Moon than on Earth by 57 microseconds per day.

Over the course of a Martian year (687 Earth days), that drift adds up to roughly 0.3 seconds — a significant offset, especially if you’re trying to coordinate spacecraft across tens of millions of miles.

The team even found subtle modulations — about 40 microseconds every 15.8 Earth years — linked to complex gravitational tugging between Earth, Mars, and the Sun.

Why Martian Milliseconds Matter

Why obsess over a few millionths of a second? Think of GPS on Earth and how useful it is. GPS depends on synchronizing satellite clocks to within billionths of a second. If our planetary cousins ever want a similar network — a Martian “internet” or interplanetary GPS — these offsets must be built into the system.

“It may be decades before the surface of Mars is covered by the tracks of wandering rovers, but it is useful now to study the issues involved in establishing navigation systems on other planets and moons,” said Ashby in a statement. “Like current global navigation systems like GPS, these systems will depend on accurate clocks, and the effects of clock rates can be analyzed with the help of Einstein’s General Theory of Relativity.”

Currently, messages between Earth and Mars can take anywhere from four to 24 minutes to arrive. That delay turns conversation into something out of the 19th century “pre-telegram communications,” as Patla put it, only with data packets instead of handwritten letters. If humans establish a synchronized Martian network, though, communications could feel much closer to real-time despite the physical delay.

“If you get synchronization, it will be almost like real-time communication without any loss of information. You don’t have to wait to see what happens,” Patla explained.

Just as Coordinated Universal Time (UTC) governs Earth, future astronauts may one day rely on Mars Coordinated Time, anchored by atomic clocks ticking on the planet’s surface. It’s the first step toward a true Solar System Internet.

Testing Einstein Across Worlds

The project also serves as a new kind of laboratory for Einstein’s theories. Mars’ changing gravitational environment offers physicists a natural experiment in time dilation — how time stretches differently across the cosmos.

Ashby and Patla’s model even incorporated solar tidal effects on Earth’s orbit, referring to the Sun’s gravitational tug subtly altering our planet’s rotation and position. This refined the precision of their Mars–Earth time comparison to within ±100 nanoseconds per day, or about the time it takes light to travel three centimeters.

“The passage of time is fundamental to the theory of relativity: how you realize it, how you calculate it, and what influences it,” Patla said in the study’s conclusion. “It’s good to know for the first time what is happening on Mars timewise. Nobody knew that before.”

The research suggests that with further refinements, including accounting for even tinier effects like orbital precession and relativistic length contraction, scientists could synchronize Martian and Earth clocks well enough to run shared systems of navigation, communication, and even finance between worlds.

Last year, NIST proposed a timekeeping framework for the Moon. The new Martian calculations take the next step: designing a scalable system of time standards for the entire inner solar system.

As NASA’s Artemis program and its “Moon-to-Mars” architecture move forward, a universal reference for time — spanning Earth, the Moon, and Mars — is increasingly becoming a reality. One day, it will be fully embedded in our communications infrastructure.

The findings were reported in The Astronomical Journal.